Emerging Trends in the Use of Recycled Sand in Mortar: A Systematic Review

Abstract

This systematic review applies the PRISMA methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) to evaluate the use of recycled sand, obtained from construction and demolition waste (CDW), in mortars for civil construction. A total of 24 studies published between 2020 and 2025 were analyzed, retrieved from the Scopus and Web of Science databases. The main objective is to assess the technical feasibility and environmental benefits of recycled sand in mortars, while addressing research gaps such as the lack of standardized methodologies and the limited understanding of durability at higher replacement levels. Given the significant resource consumption and waste generation in the construction sector, the study highlights emerging trends in adopting recycled sand as a sustainable alternative to natural aggregates. Findings indicate that optimal replacement levels range between 30 and 50% in ordinary Portland cement (OPC) mortars, and up to 100% in geopolymer mixtures when appropriate processing and activation methods are applied, without compromising mechanical performance. Reported benefits include cost reduction, lower carbon footprint, and enhanced compactness. However, challenges such as higher porosity and the need for optimized mix designs, and high heterogeneity of CDW sources and processing methods remain. Overall, the review confirms that recycled sand is a technically viable and environmentally beneficial material for mortar production, though future research must focus on harmonizing test protocols and long-term performance evaluation. In addition, a bibliometric analysis was conducted to map scientific output on this topic, identifying key countries, journals, and publication trends.

1. Introduction

Sustainability has been gaining increasing prominence when it comes to environmental issues, mainly due to the negative consequences of human actions on the planet. Issues such as global warming, pollution, excessive use of natural resources, and environmental disasters show that urgent changes are necessary. Within this context, the construction sector plays an important role, as it consumes many resources and generates a large amount of waste. It is essential that the sector adopt more circular practices and seek to reduce the use of materials extracted from nature to become more efficient and sustainable [1]. For this reason, alternatives such as the reuse of construction waste, including the production of recycled sand, have been increasingly studied and identified as viable solutions [2,3,4,5].

For this reason, States, institutions, organizations, the business sector, non-governmental organizations, and other stakeholders have acquired a greater understanding of the limitation of natural resources and the risks this represents for human survival [6]. Recent investigations have further emphasized how recycled aggregates can significantly contribute to sustainable construction practices through reducing the environmental footprint and conserving natural resources [7].

The concept of sustainability refers to human actions aimed at meeting current needs without compromising the future of the next generations. It means taking measures to keep the Earth and its biomes alive and protected, prepared to face the risks that may arise [8]. On the other hand, the construction industry is one of the sectors negatively responsible for generating environmental impacts, both due to the generation of large amounts of waste and the production of gases that contribute to the greenhouse effect, as well as the consumption of non-renewable resources [9]. Recent research has further emphasized the importance of comprehensive sustainability assessments for concrete with recycled aggregates, highlighting the need for life-cycle thinking in the selection of construction materials [10]. This perspective was reinforced by a comparative analysis of various strategies for managing construction and demolition waste using life cycle assessment methodologies [11].

Despite growing efforts to incorporate sustainability, the construction industry still faces significant barriers to effectively implementing sustainable practices. These challenges are mainly associated with the lack of adequate planning, insufficient technical knowledge of the workforce, and the absence of standardization and compliance with technical requirements, which hinder the transition toward more sustainable construction models [12].

Recent studies highlight the crucial role of the construction industry in contributing to the United Nations Sustainable Development Goals (SDGs). Sustainable practices, such as promoting sustainability-focused events, implementing education programs on sustainability, managing water resources efficiently, and developing community projects, have been identified as key strategies for fostering environmental, economic, and social sustainability in construction worldwide [13].

However, the overproduction of construction and demolition waste (CDW) can be mitigated through proper management practices. This involves not only reducing waste generation but also lowering the associated construction costs, thereby contributing to the minimization of environmental impacts. Therefore, the use of CDW is one of the actions that must be implemented in the construction sector [14]. Advances in processing technologies and quality improvement methods have significantly increased the sustainable applications of recycled aggregates from CDW [15]. Further studies have expanded these quality enhancement methods, providing a comprehensive review of techniques that can improve the properties of recycled aggregates for construction applications [16].

The processing of construction waste, such as bricks, blocks, tiles, mortars, and concrete elements, is a way to reuse these materials and reduce the environmental impacts caused by the sector. This process generates different types of recyclable materials, including recycled sand, which can be used in place of natural sand in various applications, such as bedding mortars, plaster, and even the production of non-structural concrete. The construction industry is among the activities that consume the most sand worldwide, with a demand of approximately 50 billion tons per year, making it the second most exploited resource on the planet, second only to water [17]. Therefore, considering more sustainable alternatives, such as the use of recycled sand, becomes increasingly necessary. Recent studies have investigated the feasibility of using desert sand as a sustainable substitute for traditional construction materials, highlighting how the use of local sand resources can substantially reduce reliance on energy-intensive materials such as Portland cement and clay bricks [18]. Similarly, research has demonstrated the potential of using recycled sand from excavation waste for the sustainable production of cement mortar, offering another pathway to reduce dependence on natural sand resources [19].

Although several studies point to the possibility of using recycled sand in mortars and concretes, there is still a lack of consensus regarding the impact of this substitution on the performance of the mixtures. While some research shows positive results, others suggest that adjustments in the processing methods or in the proportions of recycled sand may be important to ensure the quality of applications. In addition, the mechanical properties and durability of mortars produced with recycled sand are still topics widely debated, as these factors may vary depending on the type of waste and the technique used in processing. This systematic review specifically addresses these inconsistencies by critically analyzing the sources of disagreement, evaluating the reliability of reported results, and identifying best practices and substitution limits to ensure optimal mortar performance. In this regard, it is essential to investigate best practices and substitution limits to ensure that mortar performance is not compromised. Critical reviews have addressed aspects of durability and service-life prediction of recycled aggregate concrete, providing valuable insights into the long-term performance of these materials [20]. Complementing this, other studies have conducted long-term research on mortars with recycled fine aggregates, offering unprecedented data on the durability and aging characteristics of these sustainable materials [21].

This study aims to present the feasibility of replacing natural sands with recycled sands in mortars, based on recent research. In this context, the article addresses the following questions:

• How does the processing of construction and demolition waste (CDW) affect the properties of recycled sand?
• What recent technologies have been applied to CDW recycled sand for use in mortars?
• What are the impacts of using recycled sand on the properties of mortars, also considering its environmental and civil construction benefits?

Addressing these issues supports systematic data collection and enables this review to identify trends in the use of recycled sand from construction and demolition waste (CDW) in mortars, highlighting technological advances, environmental benefits, and economic feasibility. To ensure rigor and conciseness, it is essential that the reviewed studies are transparent, complete, and accurate, clearly stating the purpose of the research, the studies included, and the findings reported [22]. Therefore, this review adopts the PRISMA flowchart as the main framework to structure the analysis, providing a transparent overview of the data collection process and guiding the presentation of results, discussion, and conclusions.

2. Methodology

2.1. Bibliographic Analysis

To initiate the study, an exploratory bibliographic search was conducted to define the research questions to be addressed. Subsequently, a bibliographic search was performed to identify inclusion and exclusion criteria, in order to select only relevant studies. After defining the criteria, a search was carried out in journal databases, followed by a screening process using these criteria as filters, which resulted in a significant number of relevant articles for this research. The final report of the systematic review was constructed using the PRISMA flowchart.

The PRISMA 2020 methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [22] was adopted to guide the search, selection, and organization of the articles analyzed. This approach is aligned with recent comprehensive reviews in the field, which employed similar methodological rigor in their analyses of recycled aggregate concrete [23,24]. Further studies have also reinforced the importance of methodological rigor in comprehensive reviews exploring the mechanical characteristics of recycled concrete aggregates, providing a solid basis for understanding the structural behavior of these materials [25].

To initiate the research, keywords were defined according to the study objectives and thematic scope, prioritizing the most frequently used terms while maintaining a focus on waste processing, material properties, and applications in civil construction. To ensure an effective search, the Boolean operator “AND” was used to combine expressions and guarantee that only articles containing these words would be selected, thus approaching the largest possible number of articles related to the subject under study. For this purpose, the bibliographic search used the following keywords: mortar AND “construction and demolition waste”, mortar AND “recycled sand”, mortar AND “recycled fine aggregate”, and “recycled aggregate” AND mortar AND “construction and demolition waste”, searched in English to cover the widest number of works possible. To access current research, it was necessary to analyze more recent and relevant information for the study; therefore, the period chosen was from 2020 to 2025.

The journal databases used were Scopus and Web of Science, as they are multidisciplinary, cover various fields, and are highly recognized in the field of engineering, thus ensuring greater reliability. The search was conducted using the ‘All fields’ option in both Scopus and Web of Science, with the specified keywords. This ensured that all relevant articles containing these terms anywhere in the record were retrieved. In addition, they offer similar filtering tools that guarantee precise searches. The search was conducted on 21 June 2025.

In addition to the “Year of publication” criterion, the “Document type” filter was applied: only fully published articles available in PDF format were included, while preprints or articles “in press” were excluded. This ensured a solid, homogeneous, and reliable dataset.

After the initial screening, all selected scientific articles were saved in RIS (Research Information Systems) format, according to each keyword, and organized into four “collections”, where a new screening was performed to identify duplicate articles. Once duplicates were identified, they were excluded, thus generating a new total of selected articles. These articles were then exported into a single RIS file to be later used in the bibliometric analysis. Additionally, from the journal databases, the articles were exported in formats compatible with spreadsheet, where they were arranged according to their keywords, with the aim of better organization and verification to ensure that all included articles would indeed compose the analysis.

After determining and excluding duplicate articles, a new screening was necessary, during which a new spreadsheet was created and the titles and abstracts were read, to arrive at the number of articles that should be read in full and selected to compose this study.

The search retrieved 2288 records. After year/type filters and removing duplicates, 750 unique records remained for bibliometric mapping. Title/abstract screening identified 31 full texts; 24 studies met all inclusion criteria and were synthesized in the SR (Figure 1). Exclusions followed PRISMA 2020 (out of scope/insufficient data/unretrieved after documented attempts). The first exclusion criterion applied was “Year of publication,” selecting only works published between 2020 and 2025, thus excluding 731 articles outside the specified period. The second criterion was “Document type,” opting only for “articles,” which removed 315. The third criterion was “Duplicates,” excluding 492 duplicate articles. The fifth criterion was adherence to the theme “Recycled sand composed of construction and demolition waste,” discarding 719 articles. After this selection, approximately 31 articles were chosen to be read in full, of which 7 were rejected for not having the article in PDF format available in the journal portals, leaving 24 articles to be read in full and to serve as the basis for this study, presented in detail in Figure 1, represented by the PRISMA flowchart. It is worth noting that although only 24 studies were included, this number reflects a highly focused selection of the most recent and relevant research specifically addressing the use of recycled sand from construction and demolition waste in mortars. This careful selection ensures that the review provides a rigorous and meaningful analysis, directly aligned with the research objectives. The inclusion and exclusion criteria applied during the screening process are summarized in

Table 1. Inclusion and Exclusion Criteria for Article Screening.

Criterion	Details	Type
Publication period	2020–2025	Inclusion
Language	English	Inclusion
Document type	Full articles	Inclusion
Material studied	Mortars with substitution of natural sand by recycled sand from CDW	Inclusion
Concrete studies not addressing mortar separately	Excluded	Exclusion
Articles without PDF available	Excluded	Exclusion
Literature reviews	Excluded	Exclusion
Duplicates	Excluded	Exclusion
Out-of-scope articles (not about recycled sand from CDW in mortar)	Excluded	Exclusion

, complementing the PRISMA flowchart. The full checklist can be found in Table S1 of the Supplementary Material.

2.2. Bibliometric Analysis

The bibliometric analysis aimed to map and understand the scientific production on the topic. VOSviewer version 1.6.20 was used to analyze how keywords appear in the articles, which are most frequent, how they are interconnected within studies related to the topic, and the bibliographic coupling of authors. In addition, spread sheets were also used as databases, assisting in the construction of charts that illustrate the evolution of publications and citations per year, analysis of production by country, a table showing a ranking of the scientific journals that published most on the subject between 2020 and 2025, and which articles among the 750 selected obtained the highest number of citations. All these charts and tables generated in Microsoft Excel 365 used data extracted in a format suitable for processing and organized into a single spreadsheet, with the aim of supporting their construction through specific formulas.

To further illustrate the growing scientific interest in recycled sand in mortars, Figure 2 presents a quantitative analysis of publication and citation trends. The chart demonstrates a consistent upward trajectory both in the number of articles published on the topic and in their subsequent citations, with a particularly notable increase in the last two years. This trend highlights the growing relevance and impact of research in this field, strongly justifying the timeliness of this systematic review.

Figure 3 presents a chart analyzing the bibliographic coupling of authors, carried out using the VOSviewer version 1.6.20 software, which highlights the formation of three main clusters of researchers who stand out in this field of study. The largest cluster, represented in red, is led by Xiao, Jianzhuang, who not only has the highest number of publications, totaling 42, but also occupies a central position in the network, as indicated by a Total Link Strength (TLS) of 3721. This indicates that his works share a high volume of references with other researchers, demonstrating his strong interconnectedness in the field.

The second and third clusters, simultaneously led by Ma, Zhiming (blue) and Medina, C. (green), represent smaller yet significant groups in terms of collaboration and scientific impact. The TLS represented by Ma, Zhiming has a value of 1726, evidencing good integration within the network, while Medina, C., with a value of 1490, demonstrates a more concentrated activity within his own cluster, with fewer external interactions.

Table 2. Leading Authors Identified in the Bibliometric Analysis.

Nº	Author	Documents	Citations	Total Link Strength	Average Citation/Publication
1	Xiao, jianzhuang	42	1951	3721	46.45-
2	Duan, zhenhua	21	1288	2851	61.33-
3	Ma, zhiming	14	794	1726	56.71-
4	Singh, amardeep	12	720	1562	60.00
5	Madina, c	5	189	1490	37.80
6	Sáez del bosque, i.f.	4	82	1490	20.50
7	Sánchez de rojas, m.i.	5	98	1454	19.60
8	Hou, shaodan	8	714	1450	89.25
9	Del angel-meraz, ebelia	3	33	1426	11.00
10	Díaz, sergio alberto	3	33	1426	11.00
11	Magaña-hernández, Francisco	3	33	1426	11.00
12	Mora-ortiz, rené sebastián	3	33	1426	11.00
13	Wu, huixia	11	712	1362	64.73
14	Wang, changqing	7	336	1247	48.00
15	Zou, shuai	7	472	1229	67.43
16	Li, long	4	167	1142	41.75
17	Deng, qi	5	79	1086	15.80
18	Liu, qiong	8	316	1011	39.50
19	De brito, Jorge	13	263	451	20.23-
20	Mukherjee, abhijit	3	36	296	12.00

complements this analysis by highlighting the 20 most productive authors with the greatest impact. In addition to the number of documents and total citations, two indicators deserve special attention: Total Link Strength (TLS) and Average Citation/Publication. While TLS identifies how connected an author is within the research network, the Average Citation/Publication indicator reflects the average impact of each article.

As an example, the performance of the top three authors can be mentioned. Duan, Zhenhua has an average of 61.33 citations per article, and Ma, Zhiming has 56.71, surpassing Xiao, Jianzhuang in terms of average impact, even with a smaller production.

These results show that, although Xiao leads in productivity and connectivity, Duan and Ma stand out for the high relevance of each individual publication, which highlights that their works have greater visibility and influence within the scientific community.

Figure 4 present the distribution of articles published by country between 2020 and 2025, considering the 20 most productive countries. According to the study, China leads significantly, with around 210 publications, followed by India with 72 and Spain with 58. This result highlights a strong scientific output in Asian and European countries, which show the highest frequency of studies on the topic under investigation.

In contrast, traditionally influential countries in terms of international scientific production, such as the United States, appear in 13th place, while Brazil ranks 5th. This outcome may be related to the methodology adopted for country attribution, where the last country listed in the affiliation (corresponding author) was considered. It can also be directly associated with research focusing on the use of recycled sand from construction and demolition waste (CDW) in sustainable mortar production.

Countries such as China, India, Brazil, and Turkey face significant challenges in construction waste management, which promotes greater attention to practices that encourage the reuse of these materials. On the other hand, developed countries, such as the United States, possess waste management systems and advanced recycling technologies, which tend to direct their research towards new materials, standards, and waste logistics, rather than specifically toward mortar production with recycled sand. This explains their position in the ranking.

Table 3. Frequency of Articles Published Between 2020 and 2025 in the 20 Most Representative Journals.

Nº	Source Title	Frequency
1	Construction and Building Materials	117
2	Structural Concrete	68
3	Journal of Building Engineering	50
4	Materials	40
5	Sustainability	24
6	Journal of Cleaner Production	23
7	Advances in Civil Engineering	19
8	Case Studies in Construction Materials	19
9	Advances in Materials Science and Engineering	18
10	Cement and Concrete Composites	17
11	Buildings	15
12	Journal of Materials in Civil Engineering	14
13	Applied Sciences	13
14	Bulletin of the Chinese Ceramic Society	9
15	Cleaner Materials	7
16	Infrastructures	6
17	Journal of Material Cycles and Waste Management	6
18	Journal of Materials Research and Technology	6
19	Chemie Ingenieur Technik	5
20	Heliyon	5

presents the publication frequency of the selected articles from 2020 to 2025, revealing a scenario highly concentrated in a few journals. “Construction and Building Materials” leads the ranking, appearing 117 times, which clearly indicates that it is the main vehicle for research on the topic addressed. Close behind, “Structural Concrete” with 68 published articles and “Journal of Building Engineering” with 50 articles demonstrate strong presence in the field, serving as references for researchers.

The journals “Materials” with 40 articles, “Sustainability” with 24 articles, and “Journal of Cleaner Production” with 23 articles also stand out, as they present a profile that combines technological innovations, engineering advances, and sustainability concerns—an important balance for the future of civil construction. Titles such as “Advances in Civil Engineering”, “Case Studies in Construction Materials”, “Advances in Materials Science and Engineering”, and “Cement and Concrete Composites” appear with moderate participation but contribute relevantly to the advancement of knowledge.

It is worth noting that, to avoid making the table extensive and to facilitate visualization, only the 20 most representative journals within the analyzed dataset were included. This selection allows for a clear understanding of where the scientific production is most concentrated, ranging from applied research and case studies to other approaches.

In the context of this research, which addresses the use of recycled sand from construction and demolition waste as a sustainable alternative to natural sand, this bibliometric analysis shows that the topic finds space both in high-impact technical journals and in journals focused on sustainability and innovation in materials. This intersection of fields reinforces the relevance and timeliness of the study, indicating that the pursuit of environmentally responsible solutions in civil construction aligns with the growing interest of the international scientific community.

To make the chart clearer and more objective, a minimum threshold of 28 occurrences was set for term inclusion. Consequently, approximately 122 relevant keywords were selected and organized into four groups. Figure 5 presents the map generated based on these criteria, showing the main areas addressed in the analyzed articles.

The chart presents four main research clusters, differentiated by blue, green, red, and yellow colors, each representing distinct areas related to the topic “Recycled Sand in Mortars.” The most prominent keywords on the map, such as “concrete” and “construction”, stand out because they are the most cited and associated with other terms, indicating their crucial role in the research. Less visible terms, such as “CO₂”, symbolize lower frequency, yet they remain highly relevant to the study. In the term co-occurrence network, the acronyms “C&DW” and “C&D Waste” appear in the yellow and red clusters, respectively; however, for analysis purposes, they were considered equivalent to “CDW—(Construction and Demolition Waste)”, as highlighted in the red cluster.

Analyzing the chart, the blue node cluster contains the keyword with the greatest impact, “Concrete”, with a high number of occurrences totaling 834 and about 121 links. This cluster incorporates other keywords such as “RAC—recycled aggregate concrete” and “Aggregate Concrete”. It also connects with topics from other clusters, including “RFA—Recycled Fine Aggregate”, “Cement”, “Powder”, and “Fine Aggregates”. This cluster focuses on studies of recycled aggregate concrete, highlighting its mechanical performance and experimental modeling.

The green cluster highlights “Cement”, which also interlinks with other groups, encompassing keywords such as “Fine Aggregate” and “Recycled Mortar”, with a primary focus on evaluating the effects of using fine CDW on the physical and mechanical properties of mortar and related study objects.

The red cluster’s most prominent keyword is “Construction”, and it is composed of terms covering the reuse of construction materials, such as “Demolition Waste”, “CDW”, “Mix”, “Geopolymer”, and “Binder”. The terms “CDW” and “Demolition Waste” reflect both general and specific approaches in the literature, while “CDW” refers to a wide range of construction waste, with some studies focusing solely on demolition residues, justifying the separation in the co-occurrence map.

The yellow cluster appears more diffuse, containing few keywords, serving as a bridge between the clusters related to mortar and concrete. Its representative term is “Carbonation”, which has the highest occurrence within this cluster. However, due to its limited internal connections, it is considered of lower relevance to the central objectives of this study.

Table 4. Term Co-occurrence Table.

Nº	Term	Occurrences	Relevance
1	Concrete	834	0.35
2	Construction	671	0.34
3	Demolition Waste	485	0.39
4	CDW	383	1.01
5	Cement	378	0.41
6	RFA	377	1.79
7	RCA	370	1.51
8	Waste	367	0.43
9	Mixture	316	0.40
10	Powder	278	1.40
11	Increase	255	0.43
12	Recycled Fine Aggregate	235	1.86
13	Recycled Sand	232	0.76
14	Model	224	1.01
15	Aggregate Concrete	213	2.60
16	RAC	203	3.48
17	Behavior	201	0.44
18	Fine Aggregate	185	0.50
19	Treatment	178	0.63
20	Approach	164	0.52
21	Shrinkage	160	1.77
22	Natural Aggregate	160	0.50
23	Specimen	159	0.42
24	Brick	156	0.44
25	Recycled Concrete Aggregate	145	0.81

aims to present a ranking of the 25 most cited terms in the 750 articles included in this systematic review. These terms are ordered according to the number of occurrences, allowing the identification of the most frequent concepts in the literature.

Terms such as “Cement”, “Powder”, and “Aggregate Concrete” reflect technical aspects studied in the articles, related to the properties and performance of mortar produced with recycled aggregates. The relevance of each term, shown in the corresponding column, indicates the importance of these concepts within the analyzed body of publications, complementing the interpretation based on occurrence frequency.

Thus, the table provides a structured overview of the most addressed topics, serving as a reference for understanding the concepts and materials highlighted in this research and guiding future investigations in this area.

Table 5. Summary of Studies Included in the Systematic Review.

Title	Reference	Year	Citations	Purpose
Effect of Recycled Fine Aggregate on Properties of Mortar	[26]	2023	0	Evaluate the effect of different replacement rates of natural sand with RFA on the mechanical properties, durability, and microstructure of mortar.
Effect of Construction Demolition Waste as Fine Aggregate and NaOH Molarity on Strength and Fracture Parameters of Slag-Based Geopolymer Mortars	[27]	2024	7	Investigate the influence of NaOH molarity and RFA content from CDW on the mechanical and fracture properties of slag-based geopolymer mortar.
Study on the Effect of Recycled Fine Aggregate Qualities on Fly Ash/GBBS-Based Geopolymer Mortar	[28]	2023	5	Assess the effect of RFA quality and preprocessing on the fresh, mechanical, and shrinkage properties of FA/GGBS-based geopolymer mortar.
Characterization of Geopolymer Masonry Mortars Incorporating Recycled Fine Aggregates	[29]	2024	2	Evaluate the fresh, mechanical, physical, and durability properties of slag–fly ash geopolymer masonry mortars with up to 100% RFA.
Influence of Particle Size Distribution of Conventional Fine Aggregate and Construction Demolition Waste Aggregate in Portland Cement Mortar	[30]	2021	8	Compare the influence of particle size distribution of natural and CDW-derived fine aggregates on the physical and mechanical properties of mortars.
An Experimental and Environmental Evaluation of Mortars with Recycled Demolition Waste from a Hospital Implosion in Rio de Janeiro	[31]	2020	10	Assess the mechanical, rheological, and environmental performance of mortars with micrometer-scale recycled concrete aggregates from building demolition.
Evaluation of Mechanical Characteristics of Cement Mortar with Fine Recycled Concrete Aggregates (FRCA)	[32]	2021	28	Evaluate the optimal replacement level of natural fine aggregates with fine recycled concrete aggregates (FRCA) from urban C&DW in cement mortars.
Physico-Mechanical Performances of Mortars Prepared with Sorted Earthquake Rubble: The Role of CDW Type and Contained Crystalline Phases	[33]	2023	7	Evaluate how different types of recycled aggregates from earthquake CDW affect the mechanical performance of mortars, and the benefits of sorting RA by material type.
Formulating Geopolymer Mortars through Construction and Demolition Waste (CDW) Recycling: A Comprehensive Case Study	[34]	2023	4	Investigate the effects of recycled concrete aggregates on alkali-activated metakaolin mortars and their environmental potential as a low-impact building material.
Optimizing Masonry Mortar: Experimental Insights into Physico-Mechanical Properties Using Recycled Aggregates and Natural Fibers	[35]	2024	5	Analyze the physico-mechanical properties of cement mortars made with recycled concrete aggregates (RCA) and reinforced with natural fibers for sustainable construction.
Towards Sustainable Masonry Construction through Natural Aggregate Replacement by Fine Recycled Aggregates in Cement–Lime Mortars	[36]	2025	1	To evaluate the performance of mortars with natural sand replaced by fine recycled fractions from concrete and mixed waste.
Mechanical Characterization of Sustainable Mortars with Recycled Aggregates from Construction and Demolition Wastes: An Experimental Investigation	[37]	2024	0	Mechanically characterize sustainable mortars with partial or total replacement of natural sand by recycled sand from construction and demolition waste.
Impact of Recycled Fine Aggregate on Physical and Mechanical Properties of Green Mortar	[38]	2025	1	Evaluate the physical and mechanical properties of mortars with partial or total replacement of natural sand by recycled fine aggregate (RFA).
An Evaluation of the Strength for Recycled Fine Aggregate Replacement in Cementitious Mortars	[39]	2024	0	Evaluate the feasibility of recycled concrete aggregate (RCA) as a partial replacement for natural fine aggregates in mortars.
Engineering performance of high-content MgO-Alkali-activated slag mortar incorporating fine recycled concrete aggregate and fly ash	[40]	2021	14	To evaluate effects of fine recycled sand and fly ash in alkali-activated mortars.
Interfacial evaluation of geopolymer mortar prepared with recycled geopolymer fine aggregates	[41]	2020	61	To investigate feasibility and interfacial behavior of recycled geopolymer sand replacing natural river sand.
Fiber-reinforced geopolymers made with recycled aggregates for screed flooring and repair applications	[42]	2025	1	To evaluate fiber-reinforced geopolymer composites with recycled sand for flooring and repair applications.
Internal curing effect of saturated recycled fine aggregates in early-age mortar	[43]	2020	74	To investigate internal curing effects of saturated recycled sand on early-age mortar shrinkage.
Usage of recycled fine aggregates obtained from concretes with low w/c ratio in the production of masonry plaster and mortar	[44]	2022	6	To evaluate recycled sand from low w/c concretes for producing masonry plaster and mortar.
Assessing the effect of particle characteristics on the rheological properties of mortar with recycled fine aggregate	[45]	2025	1	To analyze influence of recycled sand particle characteristics on rheological properties of mortar mixtures.
Utilizing CO2 to improve plastic shrinkage and mechanical properties of 3D printed mortar made with recycled fine aggregates	[46]	2024	5	To investigate CO2 treatments improving shrinkage and mechanical properties of 3D-printed mortar with recycled sand.
Effects of water to cement ratio, recycled fine aggregate and air entraining/plasticizer admixture on masonry mortar properties	[47]	2020	56	To evaluate effects of w/c ratio, recycled sand, and admixtures on masonry mortar properties.
Environmental and technical assessment of mortars produced with recycled aggregate from construction and demolition waste	[48]	2025	1	To assess environmental and technical performance of mortars with recycled fine aggregates from CDW.
Rheological properties and compressive strength of construction and demolition waste-based geopolymer mortars for 3D-Printing	[49]	2022	91	To develop CDW-based geopolymer mortars with suitable rheology and strength for 3D-printing applications.

summarizes the 24 articles selected (as seeing in Section 2.1) as relevant to the review topic, which addresses the replacement of natural sand with recycled sand derived from construction and demolition waste in mortars. For each study, the authors, year of publication, journal, number of citations, as well as the purpose and main conclusions are presented.

The selection of articles followed the criteria defined by the PRISMA methodology, ensuring that only research directly related to the use of recycled sand in mortars was included.

This summary allows for a quick visualization of each study’s objective and its key findings, as well as providing an overview of trends, gaps, and advancements in the field. Thus, the table serves as a reference point for discussion, supporting the critical analysis of the existing literature.

3. General Discussion

After analyzing the selected articles, it was possible to identify the main trends in the use of recycled sand in mortars, as well as the impacts of this substitution on the properties of the mixtures. The results are presented below, organized according to the research questions that guided this study.

The bibliometric analysis revealed that the majority of research on recycled sand in mortars originates from China and India, and the most-cited studies focus on mechanical properties, processing methods, and emerging technologies. These publication patterns provide context for the findings of the systematic review: for instance, the prevalence of studies from these countries corresponds to the types of CDW and processing methods most frequently reported. Moreover, the topics highlighted by the most-cited articles generally align with the trends observed across the reviewed studies, indicating partial consensus on key technical challenges, while also pointing to areas where results remain divergent. This integration of bibliometric insights allows a more informed interpretation of the systematic review, linking publication trends with technical outcomes and regional practices.

3.1. Processing of CDW and Its Effects on the Properties of Recycled Sand

The literature consistently highlights that the performance of mortars with recycled sand is strongly dependent on both the characteristics of the original CDW and the processing techniques employed. Across studies, the main stages identified are crushing, sieving, washing, and, in some cases, thermal or chemical treatments, each of which has direct implications for aggregate quality and, consequently, mortar behavior [33].

There is broad agreement that recycled aggregates derived predominantly from concrete and natural stone result in mortars with superior mechanical performance compared to those obtained from ceramic fractions such as bricks and roof tiles. The higher porosity and mineralogical heterogeneity of ceramic-based aggregates explain their weaker performance, while concrete- and stone-based fractions tend to provide greater stability and strength. These differences underscore the importance of classifying CDW into homogeneous groups prior to processing, as the composition of the source material is a decisive factor for predicting mortar properties.

Several authors also emphasize the role of combining recycled and natural aggregates to mitigate performance losses, suggesting that partial blending is a viable strategy for balancing sustainability and mechanical reliability. In this context, detailed mineralogical characterization, often performed through X-ray diffraction, has proven essential to ensure reproducibility and to anticipate performance variability, particularly in large-scale scenarios such as post-earthquake debris management.

Emerging approaches such as automated CDW sorting—based not only on particle size but also on mineralogical composition and density—represent promising pathways for improving the consistency of recycled sand. By enabling the separation of higher-quality fractions and reducing heterogeneity, these techniques could expand recycling practices while aligning with sustainability and circular economy goals.

Overall, the evidence indicates that while the technical feasibility of recycled sand is established, the lack of standardized processing protocols remains a critical barrier. Without harmonization of methods such as crushing type, washing intensity, or sorting criteria, it becomes difficult to compare results across studies and to define reliable thresholds for large-scale application. The main steps involved in the processing of CDW for obtaining recycled sand are summarized in Figure 6.

Some studies exemplify how different processing approaches influence the performance of recycled sand [30,39]. A consistent finding is that particle size distribution and mineralogical composition strongly affect mortar properties, regardless of whether the aggregate is natural or recycled. For instance, a comparative analysis between crushed natural sand and recycled sand derived from CDW demonstrated that mortars with recycled sand generally performed worse [30]. However, this difference was largely attributed to the greater heterogeneity and irregular grading of the recycled material, rather than to an inherent unsuitability of recycled sand. This highlights that when processing achieves an appropriate granulometric profile, the performance gap between natural and recycled aggregates can be reduced.

Studies with recycled concrete aggregate (RCA), which represents a more homogeneous fraction of CDW, further confirm this pattern [39]. When adequately processed through crushing and sieving, RCA achieved compressive and flexural strength values comparable to natural sand at substitution levels up to 50%. Above this threshold, performance losses were observed, emphasizing that the balance between substitution ratio and processing quality is critical. These findings suggest that recycled sand does not inherently limit mortar performance; rather, inadequate processing or excessive replacement levels are responsible for negative outcomes.

The type of crushing equipment has also been shown to play a decisive role [50]. Jaw crushers typically produce more cubic particles, enhancing workability, whereas impact crushers often generate irregular grains with higher water demand. Such differences in particle morphology directly influence both rheological behavior and mechanical strength, explaining why results across studies are not always consistent.

Washing emerges as another key factor for improving recycled sand quality. Studies have shown that simple treatments such as washing and sieving can reduce water absorption of recycled fine aggregates to around 4.8%, meeting the EHE-08 limit of 5% for structural use. As a result, mortars with 25% substitution achieved compressive and flexural strengths close to the control mix, with only a 19.5% decrease in compressive strength at 28 days and even a 4% increase in flexural strength at 90 days [32]. Conversely, the absence of adequate washing increases porosity and heterogeneity, which negatively impact both fresh and hardened properties.

Finally, the presence of contaminants such as gypsum, clay, or organic matter remains a critical concern. Even small amounts can significantly compromise mortar durability and mechanical strength. Therefore, strict quality control during CDW processing is not optional but rather a prerequisite for ensuring the suitability of recycled sand in construction applications.

Table 6. CDW processing methods, recycled sand properties, and reported effects on mortars.

Reference	Processing Method	Affected Properties	Observed Effects
[30]	Crushing + Screening	Granulometry, density, absorption	Lower performance than crushed natural sand; particle size and mineralogical composition strongly affect mortar properties
[39]	Crushing + Screening (RCA)	Particle size, impurity removal	Up to 50% replacement maintains resistance close to natural; above that, significant performance drop
[50]	Crusher type (jaw, impact, cone)	Morphology and surface texture	Direct influence on workability and mechanical properties, via rheological behavior
[32]	Washing + Sieving	Absorption, particle size	Reduced absorption and better particle size distribution; performance similar to natural sand in partial replacements
[33]	Mineralogical classification of RCD (concrete, natural stone, ceramic, tiles)	Heterogeneity, porosity	Concrete/stone-rich RCD outperforms ceramic materials; mineralogical characterization is crucial
[51]	Contaminant control (gypsum, clay, organic matter)	Durability, resistance	The presence of contaminants impairs the properties of the mortar; quality control is essential

summarizes the main processing strategies identified in the reviewed studies and their impact on recycled sand properties. The comparison makes clear that while crushing and sieving are widely used, they do not fully address high porosity and absorption, whereas complementary treatments such as washing or chemical activation achieve more consistent improvements. This synthesis reinforces the importance of combining processing methods to ensure recycled sand quality and mortar durability.

3.2. Experimental Assessment of Mortars with Recycled CDW Sand

The substitution of natural sand with fine recycled aggregates (RFA) from construction and demolition waste (CDW) has proven to be a promising strategy for sustainable construction. However, challenges remain regarding the variability of the material and the mechanical and durability properties of the mortars [26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49]. The analyzed studies indicate that mortar performance depends on the replacement ratio, the type of CDW used, and the preprocessing of the aggregates.

Compressive and flexural strength are the primary criteria for assessing the feasibility of using CDW-derived RFA in mortars. Moderate substitutions of natural sand with RFA, typically up to 30–50%, result in mechanical strength comparable to conventional mortar [26,29,32,36,37,39,44], whereas higher replacement ratios can significantly reduce strength due to increased porosity, microcracks, and residual adhered paste on the aggregates [30,33,34,37,38,47]. Strategies such as washing, sieving, and particle classification have been shown to reduce these losses, enabling even full replacements while maintaining acceptable performance [26,29,32,36,40,41].

The durability of mortars with CDW RFA is influenced by characteristics such as water absorption, porosity, and permeability [26,30,33,36,43,48]. Chloride migration tests, wet–dry cycles, and freeze–thaw resistance indicate that mortars maintain satisfactory performance when replacement is partial and the aggregates are properly processed [26,31,40,46]. Scanning electron microscopy (SEM) and interfacial transition zone (ITZ) analyses highlight that ITZ compaction is crucial for preserving strength and reducing microcracking [28,29,41,42].

Other important aspects include workability and consistency, which are often affected by the high water absorption of CDW RFA [26,27,30,36,45,48]. Adjustments in water-to-cement ratio and paste-to-aggregate proportion can compensate for these variations, ensuring mortars with adequate performance. In fiber-reinforced or 3D-printed applications, CDW RFA has proven compatible, potentially improving ductility and reducing cracking [35,42,46,49].

The most frequently applied experimental tests to characterize mortars with CDW RFA include compressive and flexural strength [26,29,32,37,39], consistency and workability [26,27,30,36,44], water absorption and porosity [26,30,31,38,44], chloride migration and durability under freeze–thaw or wet–dry cycles [26,31,40,46], and microstructural evaluation by SEM and ITZ analysis [28,29,41,42]. Additional tests include shrinkage, sorptivity, 3D-printing performance, and environmental assessment [35,42,48,49].

In summary, recycled sand from CDW can effectively replace natural sand in mortars, provided that the replacement ratio, aggregate processing, and mix adjustments are considered. The use of CDW RFA contributes to the circular economy and reduces the environmental impact of construction, with technical feasibility demonstrated under various experimental conditions [26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49].

3.3. Recent Technologies Applied to CDW Recycled Sand

Technological innovations have significantly expanded the feasibility of using recycled sand from CDW in mortars. Among the most effective strategies are surface and chemical treatments, as well as aggregate pre-processing, all of which aim to reduce water absorption and enhance strength. Recent studies focusing on carbonation and polymeric coatings demonstrate consistent improvements in durability and mechanical behavior, although the balance between treatment intensity and substitution level remains crucial. For example, in geopolymer mortars with recycled fine aggregates, higher NaOH concentrations (up to 10 M) increased compressive strength by about 19–21% and flexural strength by 10–12%, while also raising the peak load to 2.6 kN. However, excessive replacement of natural sand (40% RFA) led to marked reductions in flowability (≈28–31%), compressive strength (≈23–26%), and flexural strength (≈41%), ultimately increasing brittleness [27]. These findings highlight that technological solutions are not universally positive and must be optimized to avoid trade-offs between performance and sustainability. Future work should therefore define optimal treatment intensities and substitution thresholds that maximize mechanical performance without compromising durability.

Geopolymer-based systems, especially those incorporating slag and fly ash binders, stand out for their capacity to accept up to 100% recycled fine aggregates while maintaining or even surpassing the performance of conventional cementitious mortars [29]. Beyond mechanical properties, these binders eliminate the need for water curing, reducing construction time. However, they also introduce cost and environmental trade-offs due to activator production. A key direction for future studies is the development of low-cost, environmentally friendly activators that can make geopolymer mortars more feasible for large-scale adoption.

Aggregate pre-processing, particularly the removal of very fine particles, has been shown to improve workability and strength, especially at substitution levels above 75% [28]. By reducing fines, recycled sand forms a denser interfacial transition zone, allowing better strength retention. Complementary strategies such as the integration of natural fibers (e.g., abaca, coconut, and toquilla) further enhance thermal insulation, flexural strength, and dimensional stability, though compressive strength and adhesion still lag behind mortars with natural sand [35]. These results suggest that hybrid approaches, combining recycled sand with fibers or partial blending with natural aggregates, are more effective than relying solely on untreated recycled sand. Research should now focus on optimizing fiber dosage and investigating the long-term performance of fiber-reinforced systems under real service conditions.

The influence of recycled sand fraction and source is also critical. Mortars with mixed recycled sand and fine fractions demonstrated higher initial mechanical strength than those produced with natural aggregates, while mortars with fine RCA showed inferior performance [36]. This suggests that carefully selecting waste type and fraction can prioritize specific properties, such as reduced density, higher early strength, or lower absorption, making recycled sand a flexible material adaptable to project requirements. However, since these benefits are not always maintained over time, future investigations must assess durability across different exposure conditions and mortar classes to establish reliable guidelines for practice.

Recent advances extend beyond material composition to new construction technologies. Entirely CDW-based geopolymer mortars have been successfully tested in 3D printing applications, demonstrating adequate extrusion, buildability, and compressive strength without requiring chemical admixtures [49]. These findings highlight that recycled sand is compatible with emerging digital fabrication methods, although challenges remain regarding the adhered mortar layer on aggregates, which reduces strength in alkali-activated systems [34]. Overcoming this limitation will require improvements in aggregate treatment techniques and systematic durability evaluations of 3D-printed components at both laboratory and pilot scales.

Overall, the evidence suggests that new technologies—geopolymer binders, surface treatments, pre-processing techniques, and fiber reinforcement—can substantially improve the viability of recycled sand in mortars. However, the benefits are highly context-dependent, and their large-scale adoption will depend on technical optimization combined with cost, environmental, and durability considerations.

3.4. Mechanical Properties of Mortars with Recycled Sand

The substitution of natural sand with recycled sand significantly affects both the fresh and hardened properties of mortars, and identifying optimal replacement levels is crucial to balance performance and sustainability. The majority of studies indicate that partial substitution, generally up to 30%, can lead to compressive strength values equal to or even higher than those of conventional mortars, as observed for RM30, which outperformed the reference mortar [26]. However, when substitution exceeds this range, negative effects emerge: for instance, at 28 days, RM50, RM70, and RM100 showed reductions in compressive strength of 11.7%, 12%, and 10.9%, respectively, while flexural strength decreased most noticeably in RM50 and was highest in RM70. In addition, higher substitution levels led to reduced consistency, increased chloride ion mobility, and lower freeze–thaw resistance. Microstructural analyses confirm that higher porosity, lower CH content, and irregular hydration product distribution are the underlying causes of these deteriorations, highlighting durability as the main limitation for high substitution levels.

Studies evaluating mortars with controlled particle size distributions confirm that substitution levels of up to 50% can improve both compressive and flexural strength at early ages, while 100% substitution reduces density and increases absorption, leading to weaker microstructural integrity [23]. Further evidence from mortars prepared with mixed recycled sand (containing concrete, ceramic bricks, and other small fractions) indicates that performance also depends on strength class. Low-strength mortars (M2.5) benefited from partial substitution, likely due to unhydrated cement particles contributing to strength gain, while higher-strength mixes experienced reductions that nevertheless remained within normative limits [37].

Taken together, these results demonstrate that while recycled sand can enhance strength at low to moderate substitution levels, durability concerns and fresh-state penalties become more pronounced at higher proportions. The suitability of recycled sand is therefore context-specific, depending on mortar class, mix design, and application.

3.5. Environmental Benefits of Recycled Sand

Despite the mechanical penalties at higher replacement levels, recycled sand offers clear environmental advantages. For example, mortars incorporating micro-recycled aggregates obtained from hospital demolition exhibited improved strength despite reduced workability, as the aggregates absorbed up to 4.5 times more water, lowering the effective water/cement ratio and enhancing compressive performance. Life cycle assessment (LCA) indicated notable environmental benefits, with reductions of up to 14% in ozone depletion potential (ODP) and 13% in abiotic depletion potential (ADP-f) for the best-case scenario. These advantages were observed even considering transport distances ranging from 200 to 700 km for most materials. The results demonstrate that micro-recycled aggregates can generate both mechanically robust and environmentally efficient mortars, supporting the development of eco-efficient materials and contributing to a circular economy [31].

Environmental benefits, such as reduced natural resource extraction, diversion of waste from landfills, and contributions to the circular economy, are consistently reported across studies. Full substitution, although mechanically less favorable, was considered the most eco-efficient option, illustrating that eco-efficiency and structural performance are not always aligned and that trade-offs must be carefully assessed in design choices.

Therefore, the literature converges on the idea that the technical viability of recycled sand hinges on strict quality control and optimized mix designs, while its environmental value is undeniable. Future research must focus on identifying formulations and processing methods that reconcile mechanical performance with sustainability, enabling wider adoption in the construction sector.

3.6. Critical Analysis of Limitations and Methodological Contradictions in the Literature

Although recent literature on the use of recycled aggregates from CDW in mortars and concretes demonstrates significant progress, it also reveals important limitations and contradictions that restrict comparability and hinder the consolidation of generalizable conclusions. The most recurrent challenge is the intrinsic heterogeneity of CDW, which varies widely in composition and origin, directly influencing the physical and chemical properties of the recycled sand. For instance, Ning and Lv [26] and Grabois et al. [31] analyzed aggregates obtained under distinct geographic and processing contexts, making it difficult to compare results and draw consistent conclusions. This variability highlights the need for more systematic reporting of material origin and characteristics, as outcomes are strongly context-dependent.

Differences in processing methodologies are another major source of divergence. Some authors apply pre-treatments such as washing, sieving, or impurity removal, while others use untreated recycled aggregates, as seen in Xiao et al. [23] and Vadim Grigorjev et al. [36]. Such variations directly affect parameters like water absorption, workability, and strength, explaining why certain studies report strength gains at 30–50% substitution levels, whereas others observe sharp performance declines at even lower rates. Without standardized processing protocols, it becomes challenging to identify whether performance discrepancies stem from material quality or methodological differences.

Equally problematic is the lack of uniformity in testing and evaluation criteria. Consistency, for example, is measured using different methods and at varying times, preventing reproducibility. Divergent curing ages further complicate interpretation: Xiao et al. [23] emphasized results at 14 days, while Vadim Grigorjev et al. [36] extended evaluation to 90 days, naturally leading to distinct conclusions about long-term performance. These inconsistencies weaken cross-study comparisons and slow the establishment of reliable benchmarks.

In addition, the scope and objectives of studies are highly fragmented. Some authors, such as Grabois et al. [31], incorporate environmental and life cycle assessments, while others restrict their focus to mechanical performance or mixture optimization. Although this diversity enriches the field, it also generates a fragmented body of knowledge, with limited integration between technical, environmental, and economic perspectives. As a result, the literature provides useful case-specific insights but fails to converge into universally applicable guidelines.

Overall, the contradictions observed in the literature can be traced to three main issues: the heterogeneity of CDW sources, the lack of standardized processing and characterization protocols, and inconsistent testing criteria. Addressing these limitations will require multicentric studies, harmonized methodologies, and integrated assessments that jointly consider mechanical, environmental, and economic dimensions. Only through such coordinated efforts can recycled sand from CDW be established as a robust, sustainable, and technically viable alternative in construction.

4. Practical Implications for Industry and Policy Makers

The results of this systematic review have significant practical implications for various stakeholders in the construction sector, including material producers, construction companies, and policy makers. Implementing these insights can facilitate the transition to more sustainable construction practices through the effective use of recycled sand in mortars.

4.1. Recommendations for Material Producers and Suppliers

For companies involved in the production and supply of construction materials, integrating recycled sand into their product lines represents both a challenge and an opportunity. In addition to production and supply considerations, understanding the end-users and applications of recycled sand is essential for its successful market adoption. Recycled sand can be applied in a variety of construction products, including masonry mortars, plasters, concrete blocks, and 3D-printed materials, each with specific performance requirements. Knowledge of the users’ needs, such as construction companies, prefabrication plants, or specialized contractors, helps guide processing choices and quality standards to meet application demands. Insights into market trends and practical applications can further inform producers on optimal product specifications and potential market segments, facilitating the integration of recycled sand into conventional construction practices. Based on the reviewed literature, the following recommendations can be made:

Quality control systems should be established throughout the entire recycled sand production process, from waste collection to final processing. Consistent quality control is essential for producing recycled sand with reliable properties suitable for construction applications. This includes careful source separation, removal of contaminants, and regular testing of physical and chemical properties [16].

Processing techniques should be optimized based on the intended application of the recycled sand. Different applications may require specific processing approaches to achieve optimal performance. For example, plasters may benefit from finer particle size distributions, whereas masonry mortars may require different gradations [50].

Product certification and standardization should be pursued to increase market acceptance of recycled sand products. Certification can help overcome market barriers by ensuring product quality and performance, facilitating the integration of recycled materials into conventional construction practices [7].

Investments in advanced processing technologies can improve the quality and consistency of recycled sand, potentially expanding its range of applications and market value. These technologies include sensor-based sorting, advanced washing systems, and surface treatment methods [52].

4.2. Guidelines for Construction Companies and Professionals

Construction companies and professionals aiming to incorporate recycled sand into their projects can benefit from the following guidelines derived from the reviewed research:

Mix design procedures should be adapted to account for the specific properties of recycled sand. The rheological behavior of mortars is influenced by the characteristics of recycled sand, suggesting that conventional mix design approaches may need modification when working with recycled materials [53].

Pre-soaking techniques or two-stage mixing methods can be employed to address workability issues associated with the high water absorption of recycled sand. These techniques can help maintain consistent workability without compromising the mechanical properties of the hardened mortar [54].

Specific replacement rates for each application should be established based on performance requirements. While some applications can tolerate high replacement rates, others may require more conservative approaches to maintain adequate performance. For example, non-structural applications, such as plaster mortars, may accommodate higher recycled content than structural mortars [55].

Technical training programs should be implemented to familiarize workers with the handling and application of mortars containing recycled sand. Proper application techniques are essential when using recycled aggregates, as traditional skills may need adaptation for these new materials [56].

Quality assurance protocols should be established for projects using recycled sand, including regular testing and monitoring to ensure compliance with performance specifications. Continuous performance evaluation is important to guarantee that durability and service life expectations are met [21].

4.3. Recommendations for Policy Makers and Regulatory Agencies

Policy makers and regulatory agencies play a crucial role in creating a favorable environment for the adoption of recycled sand in the construction sector. Based on the reviewed literature, the following recommendations can be made:

Construction codes and standards should be updated to explicitly address the use of recycled sand in various applications, providing clear guidelines on quality requirements, testing procedures, and acceptable replacement rates. Regulatory frameworks are important to facilitate the adoption of sustainable construction materials derived from recycled waste [57].

Economic incentives should be implemented to promote the use of recycled materials, such as tax benefits for companies incorporating recycled content in their products or projects. Economic instruments can be effective in driving the transition to circular economy practices in the construction sector [5].

Public procurement policies should be revised to include requirements or preferences for the use of recycled materials in public construction projects. Such policies can significantly reduce the environmental impact of construction activities while creating market demand for recycled products [11].

Funding for research and development should be allocated to address remaining technical challenges and expand the range of applications for recycled sand. Emerging technologies, such as 3D printing with fine recycled aggregates, can create new opportunities for the utilization of recycled materials [58].

Education and awareness campaigns should be conducted to inform stakeholders about the benefits and proper use of recycled sand in construction. Knowledge dissemination is essential to overcome resistance to adopting recycled materials in the traditional construction industry [4].

4.4. Economic Feasibility Considerations

The economic feasibility of using recycled sand in mortars is a complex issue that depends on several factors, including local market conditions, regulatory frameworks, and technical requirements. Based on the reviewed literature, the following considerations are relevant:

The cost structure of recycled sand production includes expenses for collection, transportation, processing, quality control, and distribution. These costs can vary significantly depending on local conditions and processing methods [59].

Market conditions, including the availability and price of natural sand, waste disposal costs, and demand for sustainable construction materials, significantly influence the economic competitiveness of recycled sand. In regions where natural sand is scarce or expensive, or where landfill taxes are high, recycled sand can offer substantial cost advantages [60].

Regulatory factors, such as landfill taxes, recycling mandates, and certification requirements for sustainable construction, can significantly impact the economic equation. Environmental regulations can internalize the external costs of waste disposal and resource extraction, improving the relative economic position of recycled materials [61].

Economies of scale play an important role in recycled sand production, with larger operations generally achieving lower unit costs. Industrial-scale processing of construction and demolition waste can enhance economic feasibility through efficiency gains and consistent quality [62].

Regional variations in economic feasibility are significant, with factors such as transportation distances, labor costs, and market structures creating different economic scenarios for recycled sand across regions. Local conditions in different economies can create unique opportunities and challenges for the use of recycled materials in construction [63].

By addressing these practical implications and economic considerations, stakeholders across the construction value chain can contribute to the broader adoption of recycled sand in mortars, promoting sustainability in the construction sector while maintaining technical performance and economic viability.

The economic feasibility of using recycled sand in mortars depends on several factors, including local market conditions, regulatory frameworks, and technical requirements.

Table 7. Main factors affecting the economic feasibility of recycled sand in mortars.

Factor	Description	Impact on Economic Feasibility
Cost of recycled sand production	Includes collection, transportation, processing, quality control, distribution	Higher production costs can reduce competitiveness if not offset by other factors
Price of natural sand	Local market price of natural sand	Higher natural sand prices improve competitiveness of recycled sand
Landfill taxes/disposal costs	Costs for disposing of construction waste	Higher taxes favor adoption of recycled materials
Market demand for sustainable materials	Interest from construction companies, public projects, and certifications	Higher demand increases economic attractiveness
Economies of scale	Size and efficiency of production facilities	Larger operations reduce unit costs, improving feasibility
Regional conditions	Labor costs, transport distances, infrastructure	Affects overall costs and competitiveness in different regions
Regulatory incentives	Tax benefits, mandates, or procurement policies	Incentives can make recycled sand more cost-effective

summarizes the main factors influencing economic feasibility and their respective impacts.

5. Future Research Directions

Based on the critical analysis of the current literature and the identified knowledge gaps, several promising directions for future research on recycled sand in mortars can be outlined. These research priorities are essential for advancing the field and facilitating the wider adoption of recycled sand in construction practice. Figure 7 provides a visual representation of the seven priority areas identified in this review. These areas are further discussed in the following Section 5.1 and Section 5.2, where they are grouped into broader categories for clarity.

5.1. Priority Research Areas

As illustrated in Figure 7, several research priorities are directly related to technical challenges, testing methods, and performance issues of recycled sand in mortars. These aspects are grouped and discussed below as priority research areas.

The systematic review identified seven priority areas for future research on recycled sand in mortars, each addressing critical knowledge gaps and technical challenges:

The development of standardized testing and characterization methods for recycled sand is essential to ensure consistency and comparability across research studies [51]. The need for advanced characterization techniques capable of reliably assessing the properties of recycled aggregates from construction and demolition waste has been highlighted. Future research should focus on developing standardized protocols for the characterization of recycled sand, including physical, chemical, and mineralogical properties; establishing correlations between the properties of recycled sand and mortar performance to enable performance-based specifications; and creating internationally recognized classification systems for recycled sand based on source materials and quality parameters.

Although some studies have examined the long-term performance of mortars with recycled sand, significant knowledge gaps remain regarding their durability under various exposure conditions. A 10-year study provides valuable insights but also highlights the need for more comprehensive investigations. Future research should address the long-term durability of mortars with recycled sand under aggressive environmental conditions, such as freeze–thaw cycles, chloride exposure, and carbonation; service-life prediction models calibrated specifically for mortars containing recycled sand, considering their unique degradation mechanisms; and the microstructural evolution of mortars with recycled sand over time, including changes in porosity, permeability, and phase composition [21].

The quality of recycled sand can be significantly improved through optimized processing and treatment methods. Various quality improvement methods for recycled aggregates have been reviewed, but further research is needed to develop cost-effective and scalable solutions. Future investigations should focus on energy-efficient crushing and grinding technologies that produce recycled sand with improved particle shape and gradation; advanced washing and contaminant removal techniques that minimize water consumption and waste generation; and innovative surface treatment methods that enhance the properties of recycled sand, such as carbonation, polymer coating, and nanomodification [16].

The development of advanced mortar formulations specifically designed for recycled sand can help overcome some of the limitations associated with its use. Geopolymeric mortars with fine recycled aggregates have been explored, demonstrating the potential of alternative binder systems. Future research should investigate customized binder systems that compensate for the specific characteristics of recycled sand, such as high water absorption and variable composition; multicomponent mortar formulations incorporating supplementary cementitious materials, chemical admixtures, and fibers to enhance performance [29]; and self-healing capabilities in mortars with recycled sand, based on the work of Gupta & Kua on self-healing concrete with recycled aggregates [64].

A comprehensive assessment of the sustainability of mortars with recycled sand is essential to understand their true environmental, economic, and social impacts. Comparative life-cycle assessments of construction and demolition waste management strategies have been conducted, but more integrated approaches are required. Future research should focus on holistic life-cycle assessment methodologies that consider all relevant environmental impacts, including resource depletion, emissions, and waste generation; economic analysis frameworks that account for direct costs and externalities, allowing fair comparisons between conventional and recycled materials; and social impact assessment tools that evaluate broader social implications of using recycled sand, including job creation, health effects, and community benefits [11].

The transition from laboratory research to industrial-scale implementation of recycled sand in mortars presents numerous challenges requiring dedicated research efforts. Technical and environmental aspects of using recycled construction and demolition (C&D) sand in various applications have been evaluated, but further work is needed to increase production and utilization at scale. Future research should address process optimization for industrial-scale production of recycled sand, focusing on efficiency, consistency, and quality control; supply chain management strategies for recycled sand, including collection, processing, distribution, and market development; and case studies and demonstration projects showcasing successful industrial applications of mortars with recycled sand, providing practical examples and lessons learned [62].

The development of supportive policies and regulatory frameworks is crucial to facilitate the adoption of recycled sand in construction practice. The current status and future prospects of sustainable construction materials from recycled waste have been discussed, emphasizing the importance of enabling policies. Future research should investigate performance-based regulatory approaches that focus on the functional requirements of mortars rather than prescriptive material specifications; policy instruments that effectively incentivize the use of recycled materials, such as tax benefits, subsidies, and sustainable public procurement; and standardization and certification systems that provide quality assurance for recycled sand products, increasing market confidence and acceptance [57].

5.2. Opportunities for Interdisciplinary Research

Beyond the technical aspects highlighted in Figure 7, other priority areas emphasize the importance of interdisciplinary research and cross-sector collaboration. These opportunities are discussed in this subsection.

In addition to the seven priority areas identified above, there are significant opportunities for interdisciplinary research that combines expertise from multiple fields to address complex challenges related to recycled sand in mortars. The integration of digital technologies, such as artificial intelligence, machine learning, and blockchain, offers promising avenues to optimize recycled sand production, quality control, and supply chain management. Recent advances in 3D printing technology using fine recycled aggregates illustrate the potential of combining digital fabrication with sustainable materials [58]. Collaborative research among materials scientists, structural engineers, architects, and environmental scientists can lead to more holistic approaches for the development and implementation of mortars with recycled sand. The importance of multi-disciplinary perspectives to address the complex challenges of construction and demolition waste recycling has been emphasized [4]. Partnerships among academia, industry, and government can facilitate the translation of research results into practical applications and supportive policies. The importance of stakeholder collaboration in implementing circular economy strategies for construction and demolition waste has been highlighted [5].

By pursuing these research directions and interdisciplinary opportunities, the scientific community can address the remaining challenges and knowledge gaps related to recycled sand in mortars, paving the way for its broader adoption in sustainable construction practices.

6. Summary and Conclusions

This systematic review combined bibliometric mapping and systematic analysis of 24 studies (2020–2025) to investigate the feasibility of replacing natural sand with recycled sand obtained from construction and demolition waste (CDW) in mortars. The research applied the PRISMA methodology to ensure methodological rigor and transparency, while also integrating bibliometric tools to highlight publication trends, key authors, and regional contributions. The combined approach provided a comprehensive overview of both the technical performance and the environmental benefits of recycled sand in mortars.

The results confirmed that recycled sand can partially or fully replace natural sand in mortars without compromising performance under optimized conditions. Mechanical properties such as compressive and flexural strength are often preserved or even enhanced at substitution levels of 30–50% in cement-based mortars, and up to 100% in geopolymer mixtures when combined with appropriate processing and activation methods. Moreover, environmental assessments consistently indicate that recycled sand reduces natural resource depletion and landfill disposal, reinforcing its role in the transition toward a circular economy in construction. However, despite these benefits, the review also identified significant methodological contradictions and performance variability across studies.

The following conclusions can be drawn:

• High heterogeneity of CDW sources and compositions is the primary barrier to large-scale application of recycled sand in mortars, as variability in origin and mineralogy directly affects mechanical and durability outcomes.
• Lack of standardized methodologies for processing and testing recycled sand limits comparability across studies, preventing the consolidation of universally applicable guidelines.
• Optimal substitution ranges have been identified: up to 30–50% for cement-based mortars and up to 100% for geopolymer mortars, provided that advanced processing and treatment methods are applied.
• Technological solutions, including carbonation, polymeric coatings, and fiber reinforcement, show promise but require optimization to balance performance, cost, and environmental trade-offs.
• Environmental benefits are consistently observed across studies, with recycled sand contributing to resource conservation, waste reduction, and lower carbon footprint.
• Specific implications for stakeholders emerge from this synthesis, indicating that researchers should focus on harmonizing processing and testing protocols and expanding long-term durability studies; industry professionals can adopt partial replacement strategies supported by rigorous quality control to ensure reliable performance; and policymakers have a role to play in updating construction standards and promoting economic incentives that encourage the adoption of recycled aggregates.

Overall, this review highlights that while recycled sand is technically feasible and environmentally beneficial, its wider adoption requires overcoming heterogeneity and methodological inconsistencies. By synthesizing diverse findings and outlining practical pathways for researchers, industry, and policy makers, this study contributes to advancing the sustainable use of recycled sand in mortar production.