Previous Article in Journal
Cost-Effective Perspective of Fiber-Reinforced Geopolymer Concrete Under Different Curing Regimes
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Construction Materials
Volume 5
Issue 4
10.3390/constrmater5040082
constrmater-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement

by
Ali Abbas
* and
Anjana Kudukkan
School of Architecture, Computing and Engineering, University of East London, 4-6 University Way, London E16 2RD, UK
*
Author to whom correspondence should be addressed.
Constr. Mater. 2025, 5(4), 82; https://doi.org/10.3390/constrmater5040082
Submission received: 29 September 2025 / Revised: 6 November 2025 / Accepted: 11 November 2025 / Published: 19 November 2025
Browse Figures
Versions Notes

Abstract

The present experimental study was set up to examine the use of waste seashells (ground to powder form) to replace cement partially and as a filler material in concrete. Two distinct particle size ranges of seashell powder were adopted based on their intended function: 63–125 micron particles are used as a filler to enhance packing density, and 0–63 micron particles are used as a cement replacement to improve reactivity. Four concrete mixes, including a control mix, were designed, with ground seashell powder used to replace cement, both as a filler replacing 15% of the cement and additionally as finer seashell powder replacing 0, 15, and 30% of cement (labelled S0F15, S15F15, and S30F15, respectively). The seashells’ chemical, physical, and mineralogical properties were characterised using particle size analysis through sieving, X-ray diffraction (XRD), Scanning Electron microscopy (SEM), and pH test methods. Furthermore, the fresh properties of concrete, such as initial and final setting time, were studied. The hardened seashell-based concrete was subjected to direct compressive strength, bulk density, and modulus of elasticity analysis. The results showed that the 28-day compressive strength of concrete with seashells was moderately reduced by nearly 25% compared to the control mix. In the case of modulus of elasticity, the reductions were about 5%, 7% and 13% for mixes S0F15, S15F15 and S30F15, respectively, compared to the control mix CM. Finally, the carbon emission from concrete with 15% and 30% seashell powder content as cement replacement (plus 15% cement replaced with the powder acting as a filler in both cases) resulted in a notably lower carbon emission of 250 and 212 kg CO2 e/m3, respectively, compared to the control mix, with a reduction of approximately 24%. This is a sizable reduction in Global Warming Potential (GWP) value. Therefore, the study concluded that the investigated seashell powder in concrete could benefit an eco-friendly environment and conservation of natural resources.

1. Introduction

Concrete remains one of the most widely used construction materials worldwide due to its versatility, durability, and cost-effectiveness. However, the production of ordinary Portland cement (OPC)—a key component of concrete—is highly energy-intensive and accounts for approximately 7–8% of global CO2 emissions. This environmental challenge has driven extensive research toward identifying sustainable supplementary cementitious materials (SCMs) that can partially replace cement and reduce the embodied carbon of concrete. Conventional SCMs such as fly ash (FA) and ground granulated blast-furnace slag (GGBFS) have been successfully employed to enhance mechanical and durability properties while lowering carbon emissions [1,2,3,4,5,6,7,8]. These industrial by-products possess pozzolanic reactivity, allowing them to consume calcium hydroxide released during cement hydration and thereby improve the long-term strength and microstructural performance of concrete. However, with the gradual decommissioning of coal-fired power plants and shifts in industrial production, the global availability of FA and GGBS has declined, creating a pressing need to explore alternative low-carbon binders and fillers. In recent years, attention has increasingly turned toward bio-derived and waste-based materials—such as rice husk ash, bamboo fibres, and hemp—as renewable and eco-efficient alternatives [9]. Among these, seashell waste has emerged as a promising alternative due to its high calcium carbonate (CaCO3) content, abundance, and ease of processing. Discarded seashells from the seafood and canning industries often pose environmental disposal issues, particularly in coastal regions. Their chemical composition—approximately 95% CaCO3 with traces of elements such as Mg, Na, Fe, and Zn—closely resembles that of natural limestone used in cement production. The structure of seashells consists of three fundamental components:
  • The outer layer, which is composed of a protein matrix, provides strength and protection.
  • The middle layer, made of calcite, a crystalline form of calcium carbonate, contributes to the shell’s shape and stiffness.
  • The inner layer is characterised by a highly ordered arrangement of calcium carbonate crystals.
One notable feature of seashells is their porous quality, adding to their distinctive properties as a building material. Seashells are highly porous, which makes them ideal for various applications, particularly in eco-friendly building materials. They offer improvements in thermal and acoustic properties and serve as a sustainable alternative to synthetic materials in construction. Seashells sourced from the canning industry can effectively replace conventional aggregate [10,11,12,13,14,15,16,17,18,19,20,21], cement, or filler in concrete. Their high calcium carbonate (CaCO3) content is comparable to that of finely ground limestone particles. When seashells are subjected to extremely high temperatures, they are converted into calcium oxide (CaO) and carbon, resulting in enhanced strength and density of concrete. The CaO content of seashells varies based on the calcination temperature.
Compared to the traditional supplementary cementitious materials such as Fly ash (FA) and GGBFS, seashell powder demonstrates distinctive mechanical and environmental characteristics. While FA and GGBFS primarily contribute to pozzolanic reactions that improve the long-term strength, seashell-based binders may show comparable or slightly lower early-age strength; they demonstrate promising long-term strength development due to their high CaCO3 content and filler effect, which enhance the microstructure and density of the cement matrix while reducing the porosity when properly processed. Moreover, seashell powder, owing to its potential CaO content, can further contribute to early strength gain through partial hydraulic reactions. In terms of sustainability, seashell-based materials possess a significantly lower embodied carbon footprint, as they are derived from naturally occurring marine waste rather than energy-intensive industrial by-products. Processing waste seashell into powder requires substantially less energy and emits considerably less CO2 than the production and grinding of FA and GGBFS, positioning seashell powder as a viable and eco-friendly alternative for partial cement replacement. Consequently, seashell powder presents a competitive advantage as a low-carbon, calcium-rich SCM, particularly in coastal regions where the disposal of shell waste poses environmental challenges.

2. Research Aim and Outline

The research was aimed at examining seashells use as cement in low-carbon concrete. In the present study, seashell powder with particle sizes ranging from 63–125 microns was used as a filler material (replacing 15% of the cement) plus particle sizes 0–63 microns (used as direct cement replacement at ratios of 0%, 15% and 30%). The control mix (i.e., without any replacement) was designed to achieve a cube compressive strength of 40 MPa (i.e., C40 mix proportions) with 52.5-grade CEM I cement. The mechanical performance of the finished concrete will be evaluated in the laboratory, including density, workability, compressive strength, microstructural properties, modulus of elasticity, and permeability. The study will also evaluate the reduction in carbon emissions and energy use, demonstrating the ability of seashells to reduce the embodied carbon in concrete.

3. Literature Review

The development of low-carbon concrete with seashells as a filler ingredient has the potential to pave the way for sustainable building approaches. Seashells are a byproduct of the seafood industry and are readily available in coastal areas. They have unique properties, including a high calcium carbonate concentration. The research aims to analyse seashell material, improve concrete mix designs, evaluate environmental effects, and conduct feasibility studies to create concrete with low carbon emissions, using seashells as a renewable resource. Today, civil engineers’ environmental concern has a significant impact on construction material innovation. To increase societal well-being, a myriad of innovative approaches and sustainable building material options can be integrated into construction activities. Concrete is widely used in everyday life due to its availability and versatility. It is necessary for construction projects all around the world. However, excessive usage of concrete causes major environmental difficulties, including significant carbon emissions and environmental risks during extraction. Efforts to reduce carbon emissions and environmental impact are crucial to address climate change. To protect the environment, it is crucial to properly dispose of waste and prioritise recycling. Seashells significantly contribute to global waste due to the fishing and seafood industries. Improper disposal of seashells in the ocean, sea, and coastline has led to serious environmental damage. Seashells are mainly made of calcium carbonate, like limestone, with small amounts of sulphate and chloride salts.
Many investigations have been conducted to discover whether waste items from our environment can be used instead of concrete elements. This research was driven by the desire to optimise the use of raw materials for sustainable growth, as well as the growing need to protect the environment. As a result, in addition to considering when designing structures, civil engineers have focused on creating structures that meet serviceability standards. Research on the process of adding solid waste to cement-based materials has been ongoing for a long time [22]. It is critical to implement a strategy that includes decreasing and substituting concrete materials to reduce the amount of carbon emissions associated with concrete manufacturing. Certain industrial waste materials have been proven to be efficient coarse aggregate substitutes, resulting in lightweight aggregate concrete that significantly improves sustainability objectives. However, much more research and analysis are needed on replacing cement in concrete [23]. The shapes and compositions of seashells, such as mussels, clams, oysters, and scallops, vary greatly. Approximately 5% of them are composed of organic material, with the remainder composed of inorganic salts such as potassium (K), sodium (Na), magnesium (Mg), iron (Fe), zinc (Zn), selenium (Se), and other elements, resulting in 95% calcium carbonate. Seashells are made up of three fundamental structural components. The outer layer consists of a protein matrix that provides the shell with strength and protection. Calcite, a crystalline type of calcium carbonate, provides shape and stiffness to the intermediate layer. The inner layer consists of a highly orderly arrangement of calcium carbonate crystals. Seashells are distinguished by their porous quality.
Bamigboye et al. [24] previous investigations on the usage of seashell powder as a cement replacement focused mostly on the cement’s environmental impact. These studies, however, have not considered the likelihood that diminished mechanical properties will result in a greater total environmental impact. This is because, to achieve specific mechanical performance criteria, more concrete is necessary. As a result, it remains difficult to identify optimum Ordinary Portland Cement (OPC) and seashell powder ratios that are optimised for both mechanical and environmental properties. According to Leman et al. [25], crushed seashells were used in place of fine aggregate to generate self-compacting concrete. Studies by Wang et al. [26] and Bamigboye et al. [27] suggest that seashells could someday replace traditional limestone in cement production. For more than 20 years, different research initiatives have investigated the practicality of utilising seashells as a replacement for gravel in concrete. Some studies discovered that waste generated in the building sector is an issue, particularly in the aviculture and aquaculture industries, which produce substantial amounts of shell debris. When discarded, these shells endanger both human health and the environment. To address this issue, scientists have investigated the use of shell particles as bio-fillers while manufacturing gypsum plaster. These studies entailed processing and mixing varied amounts of shell powder (from scallop and conch shells) into gypsum plaster. Mechanical, thermal, and durability tests were performed on the finished plaster to determine the efficacy of the shell powder as a filler. The results showed that substituting shell powder for gypsum plaster enhanced mechanical characteristics, thermal performance, and water resistance. The study by Bamigboye et al. [27] investigates the most recent research on the mechanical and long-term qualities of concrete that incorporates seashells wholly or partially to replace traditional building materials. It covers a variety of subjects, including the types of waste seashells used, the procedures for preparation and treatment, the chemical composition, the physical features, and the mechanical and durability test methodologies used in previous studies. Concrete-containing seashell substitutes exhibit strength losses as compared to control mixtures as the replacement ratio increases from 5% to 75%. However, mechanical strength increases proportionally with curing age, particularly up to 90 days. Durability properties varied depending on the percentage of seashells used.
Bamigboye et al. [27] conducted a study to develop more sustainable and profitable concrete production processes. This study investigates the feasibility of using Senilia senilis seashells as a partial substitute for fine aggregates. Several laboratory investigations found that crushed seashells lowered workability while retaining acceptable handling and consistency properties. Blends with 10% and 20% seashells met the strength standards for construction with mild exposure. However, as the number of seashells rose, compressive strength fell. Shell blends of 30% to 100% could be employed in construction projects that require M15-grade concrete and low-bearing structures, respectively. When mixed with 10–50% seashells, the split tensile strength increased and met the criteria after 28 days of curing. Finding a sustainable OPC replacement is critical given the cement industry’s enormous contribution to global CO2 emissions. Because leftover seashells contain a high calcium carbonate content, the study discovered that they might be an effective addition to blended cement. To lessen the negative environmental implications of typical cement production, such as resource depletion and CO2 emissions, the study suggests replacing OPC with SHP. The appropriate SHP dosage for OPC replacement is obtained after examining 34 cement mixtures. Othman and Johari [28] investigated the use of cockle shell ash (CSA) as a partial cement replacement in concrete for sustainable buildings. The results revealed that CSA influenced concrete parameters such as compressive strength, tensile strength, elastic modulus, and porosity. Longer curing durations enhanced strength when compared to standard concrete, but total strength dropped as the CSA portion increased. CSA has the potential to be a long-term replacement for traditional methods, but its effects on concrete, particularly strength and durability, should be carefully examined.

4. Materials and Methods

4.1. Raw Materials

Portland cement is a commonly utilised construction material in the construction industry. Comprised of limestone, clay, and various minerals, it is processed into a fine powder and offers different variations tailored to specific properties and applications. One such variation, Hanson Portland Cement CEM I 52.5 N, is prevalent in the UK and boasts a compressive strength of 52.5 MPa after 28 days of curing. This type of cement finds extensive use in applications such as concrete, precast elements, and high-rise constructions. Adhering to the manufacturer’s guidelines is crucial for optimal results. In the present study, Jewson Sharp concrete sand was used as the fine aggregate. This sharp sand, also called coarse sand or grit sand, possesses larger particle sizes than other sand varieties, such as builder’s or play sand. It is commonly employed in concrete or mortar mixtures, enhancing their strength, stability, workability, and material bonding. The sand’s sharp edges contribute to forming a robust interlocking structure within the concrete. Jewson, a reputable building materials provider in the UK, offers this type of sand. When utilising this sand, it is crucial to adhere to precise mixing ratios and techniques to achieve the desired strength, durability, and finish in our applications. Additionally, coarse aggregates constitute vital elements of concrete, providing strength, durability, and volume. These aggregates, with particle sizes ranging from 4.75 to 40 mm, are categorised based on their size and place of origin. Common forms of coarse aggregates include crushed stone, gravel, and recycled aggregates. They are used to fill the voids between fine particles and cement, resulting in a dense mix that enhances the concrete’s mechanical properties. For our study, we used 10 mm and 20 mm sizes of coarse gravel aggregates. The determination of physical properties, such as particle size distribution, water absorption, and specific gravity, was carried out by Eurocodes and is mentioned in Table 1.
The seashell powder used in this study was prepared from waste scallop seashells collected from seafood processing industries. The shells were thoroughly cleaned with fresh water to remove organic residues and surface contaminants, oven-dried at 105 °C for 24 h, and subsequently ground using a ball mill. The resulting powder was sieved to obtain two fractions: 63–125 μm (used as filler) and 0–63 μm (used as cement replacement). Comprised primarily of calcium carbonate (CaCO3), accounting for over 90% of their composition, seashells also contain contaminants and dust. Chemically akin to limestone aggregates, seashells also contain trace amounts of sulphate and chloride salts. Their interior layer consists of a well-organised arrangement of calcium carbonate crystals, contributing to their distinct characteristics. The porous nature of seashells enables high permeability to ions, gases, and liquids, making them suitable for various applications, particularly as effective building materials that require adsorption [29]. Subject to elevated temperatures, the calcium carbonate in seashells transforms into calcium oxide (CaO) and carbon, augmenting their potential for concrete production. The substantial calcium carbonate content is essential, as it transitions to calcium oxide, enhancing both the strength and permeability of concrete, rendering seashells an appealing material for sustainable construction methodologies [30].

4.2. Particle Size Distribution (PSD)

The particle size distribution (PSD) curve presented in Figure 1 illustrates the gradation characteristics of the selected materials: coarse aggregate (10 mm and 20 mm), fine aggregate (FA), and seashell powder. The curve indicates that the coarse aggregates (CA 10 mm and CA 20 mm) exhibit a relatively narrow size range with steep slopes, representing their well-defined gradation. The fine aggregate (FA) shows a broader distribution with finer particle sizes, ensuring good packing and filling of voids within the mix. The seashell powder, on the other hand, presents an even finer gradation, predominantly in the micro-size range, highlighting its potential role as a filler material [31]. The seashell powder filler range was 63–125 micron (as can be seen in the PSD curve), whilst particles smaller than 63 micron were used as a cement replacement to improve reactivity.
This gradation behaviour is significant because a well-graded combination of coarse, fine, and filler particles contributes to improved packing density, reduced voids, and better mechanical interlocking in concrete or mortar mixes. The inclusion of seashell powder alongside conventional aggregates can therefore enhance the overall performance of the composite material, particularly in terms of workability and durability.

4.3. Mix Design and Specimen Preparation

The present research work is carried out by using a C40 concrete mix design, which contains Portland cement type CEM I, fine aggregate, coarse aggregate (10 mm and 20 mm), and water. The exact mix proportions will be determined by the project’s specific requirements as well as the qualities of the materials employed. After 28 days of curing, it achieved a compressive strength of 40 KN/mm2. The C40 mix was designed in accordance to British Standard BS EN 206:2013+A2:2021 [32] and Building Research Establishment (BRE) mix design guide [33]. Different mix combinations were prepared using seashells. From the literature review, the optimum percentage of partial replacement of cement using seashells was found to be 0%, 15%, and 30% respectively. Mixed quantities per cubic meter are summarised in Table 2. Compressive strength test, stress–strain behaviour, SEM, and XRD were conducted for all mixes.
The process of concrete casting commences with the meticulous weighing of cement, sand, seashells, coarse and fine aggregates, and water by the prescribed mix design. To assess compressive strength, three cubes are utilised, while three cylinders are employed to determine the modulus of elasticity for each mix. After accurately blending the components with a mixer machine for 5 min, the concrete’s workability was evaluated using a slump test in accordance to British Standard BS EN 12350-2 [34]. The moulds are thoroughly cleaned, and a mould release agent or oil is applied to prevent adhesion. A freshly prepared concrete mix is poured into the moulds in three layers, each manually compacted using 25 strokes of a tamping rod, following the procedure outlined in BS EN 12390-2 for manual compaction. This ensures maximum density and removes air spaces. Trowels are then used to flatten the top surface and eliminate excess concrete from the mould edges. Upon demoulding, the specimens are immersed in a curing tank (supplied by Matest, Arcore Italy) for 28 days to facilitate proper hydration and strength development.
In the present study, the focus was on evaluating the 28-day compressive strength of concrete mixes incorporating scallop seashell powder, as this age is widely adopted for standard structural performance assessment and comparison with conventional concrete. Whilst long-term strength development (e.g., at 56 and 90 days) was beyond the scope of the current experimental program, we acknowledge its importance for understanding the complete strength development trend (and potential additional sustainability benefits of strength gain with aging).

4.4. Calculation of Carbon Emission

The carbon emissions in the present study consider emissions arising from the preparation and testing of materials within laboratory conditions (and excludes material collection and transportation emissions). For the presently proposed seashell powder SCM and filler material, a new embodied carbon factor has been determined, which includes emissions from laboratory processing (grinding and sieving), and corresponding energy consumption by equipment used. Thus, the power consumption in these activities was calculated (i.e., ~0.00318 kWh/g), in addition to considering the real-time carbon emissions data for electricity consumption (provided by Nowtricity in 2024 [35]), which indicated a carbon intensity of 185 g CO2/kWh). Therefore, the carbon emission factor for seashell powder was found to be 0.059 kg CO2 per kilogram of seashell powder.
Emission factors for conventional materials—cement, aggregates, sand, and water—were obtained from the guide by Institution of Structural Engineers [36] as shown in Table 3. For seashell powder, the emission factor was determined experimentally based on measured power consumption during processing.

5. Results and Discussions

5.1. Density of Concrete

The density of concrete is influenced by several factors, including material proportion, mix design, and the type of cementitious materials utilised. Typically, the density of normal concrete ranges from 2200 to 2500 kg/m3. Research findings reveal that the density of concrete decreases when seashells are added, resulting in lighter concrete as the percentage of cement replacement increases, as depicted in Figure 2. The results show that the density of the control mix after 28 days is 2515 kg/m3, whereas with 30% seashell replacement, the density decreases to 2458 kg/m3. However, the decrease is very small, ranging from 0.99% to 2.27% of the control mix (as the percentage of partial replacement of cement and the filler effect of seashells increases [37]).
Seashells often exhibit porosity, leading to the presence of voids or pores within their structure. This porosity results in the formation of air pockets in the mix, consequently reducing its density. Moreover, the calcium carbonate present in seashells reacts with cement hydration products, potentially causing the formation of pores and further contributing to decreased density due to this chemical reaction. The specific gravity and water absorption ratio of fine and coarse aggregates used in the present study, as well as that of the seashell powder, are summarised in Table 2, which shows that the latter has a water absorption ratio of ~1.42%. Additionally, seashells undergo volume changes during the mixing and compaction processes, leading to a reduction in the compactness of the concrete and ultimately contributing to a decrease in density.

5.2. Initial and Final Setting Time of Concrete Mixes

The findings of the experimental study, shown in Figure 3, indicate the average of three independent measurements of setting times for each mix. Incorporating seashells into the mix resulted in a retardation effect compared to the control mix. The initial setting time showed a 30% increase compared to the control mix when seashells were added at a 30% partial replacement, while the final setting time decreased by 12% relative to the control mix. The control mix had an initial setting time of 215 min, which extended to 280 min with the addition of seashells. This demonstrates the delayed setting time when seashells are included as filler material.
The delayed initial setting time of concrete can be attributed to the porous nature of seashells, which can absorb water from the mix. This water absorption diminishes the available water for the hydration reaction, thus decelerating the setting time. Moreover, the partial substitution of cement by approximately 30% leads to a decrease in the overall cement content within the mix. Since cement is the primary binder responsible for the setting and hardening of concrete, its reduced presence can also contribute to a delayed setting time. Furthermore, an increase in the filler material content may result in a denser mix, necessitating more time for the hydration of cement and the setting process. According to BS EN 197-1 [38], the final setting time of cement should fall within the range of 60 to 600 min. All mix combinations conformed to the stipulated setting time range by the code. In comparison to the control mix, the final setting time is reduced by 13% when cement is partially replaced by seashells and the same material is used as a filler in the concrete. This faster setting time of concrete containing seashells can be attributed to the porous structure and water absorption capability of seashells.

5.3. Compressive Strength Test

The specified target strength for the control mix was 40 N/mm2. After 28 days of curing, the achieved compressive strength was measured according to BS Standards was 51.57 MPa with a standard deviation of ~2.93%. The compressive strength of different mix combinations is displayed in Figure 4, showing a moderate descending trend. The highest strength was observed in a mix without any partial replacement of cement with seashells, but with the inclusion of 15% seashell filler. This is almost the same value as that of the control mix. On the other hand, the mix featuring 30% partial replacement demonstrated ~25% reduction in strength over the control mix.
The composition of seashells typically consists of approximately 95–97% calcium carbonate (CaCO3) along with traces of organic and inorganic matter. It is recommended to wash seashells before use to reduce these contaminants. Additionally, calcium oxide (CaO) is a vital component for enhancing the strength and increasing the density of concrete. However, beyond a 15% proportion of seashells in concrete, there is a decline in compressive strength, which can be attributed to the increased effective surface area leading to inadequate cement paste coverage and reduced bonding properties within the matrix and aggregate [39]. Nevertheless, incorporating up to 15% seashells in concrete as a filler can lead to increased strength, attributed to the higher concentration of CaO present in the shells. The inclusion of seashell particles in cement matrices leads to a reduction in compressive strength due to the smaller size, less rounded shape, and poorer internal particle organisation of the seashell particles compared to cement. This is further exacerbated by the more porous surface of seashell particles, which increases the number of pores and weakens mechanical properties through intensified interaction with cement particles. Seashells’ relatively high-water absorption capacity also plays a role in weakening the interfacial bond between aggregates and cement paste, consequently reducing overall strength.

5.4. Modulus of Elasticity

The stress–strain behaviour of concrete is a fundamental mechanical property, initially showing elastic deformation under applied load, followed by plastic deformation, cracking, and eventually failure. Experimental results from the tested concrete cylinders (diameter × height = 100 mm × 200 mm, in accordance with BS EN 12390-13 [40]) demonstrate variations in the modulus of elasticity with different replacement levels of cement using seashells and fillers, which is shown in Figure 5. The control mix (CM) exhibited a modulus of elasticity of 34.16 GPa, while the mixes with seashells showed decreases as the replacement ratio was increased. The reductions were about 5%, 7% and 13% for mixes S0F15, S15F15 and S30F15, respectively, compared to the control mix CM.
These results suggest that the inclusion of seashells up to an optimum level does not drastically affect the stiffness properties of the resulting concrete material. Seashell powder can play a positive role by improving the interfacial transition zone (ITZ) between the cement paste and aggregate. The physical and chemical characteristics of seashells play a crucial role in this enhancement. Being rich in calcium carbonate, seashells can partially react with cement hydration products, contributing to the formation of additional calcium silicate hydrate (C–S–H) gel. This reaction strengthens the ITZ and leads to a denser microstructure. Additionally, the filler effect and pozzolanic reactions of silica in seashells can also help reduce voids and refine pore structures. However, as the replacement increases, the reduced cement content limits the extent of hydration reactions, which explains the increased reduction in the modulus of elasticity compared to the control specimen [41]. Thus, the findings indicate that seashells can positively influence the concrete matrix without drastically reducing its stiffness characteristics (with the benefits being most pronounced at moderate replacement levels).

5.5. Scanning Electron Microscopy (SEM)

The SEM micrographs presented in Figure 6a–c illustrate the microstructural variations between the control mix and the seashell powder–modified concretes. The control sample (Figure 6a) exhibits a relatively porous matrix with distinct microcracks and visible pore regions. In contrast, mixes incorporating seashell powder (Figure 6b,c) show a noticeably denser structure with fewer microcracks and a reduced pore network. This reduction in porosity can be attributed to the filler effect of finely ground seashell particles, which occupy the voids within the cement matrix and enhance the overall packing density of the composite. The improved particle packing decreases capillary pore continuity, resulting in a more compact and refined microstructure [42,43,44].
Furthermore, the presence of additional calcium silicate hydrate (C–S–H) gel formations is evident in the seashell-modified mixes (Figure 6b,c). The incorporation of seashell powder, which is rich in calcium carbonate (CaCO3), promotes secondary hydration reactions between the liberated calcium hydroxide (Ca(OH)2) and reactive silica phases in the cement paste. This pozzolanic-type reaction results in the generation of additional C–S–H compounds, contributing to matrix densification and strength development. The increased formation of C–S–H gel enhances the bonding within the interfacial transition zone (ITZ), leading to improved microstructural integrity and reduced microcracking. Overall, the SEM observations confirm that partial replacement of cement with seashell powder reduces porosity and promotes the formation of additional C–S–H phases, thus improving the microstructural compactness and durability of the concrete system.

5.6. X-Ray Diffraction (XRD)

Figure 7 illustrates the X-ray diffraction (XRD) patterns of the control mix (CM) and the mixtures containing 0%, 15%, and 30% seashell powder replacement, along with the corresponding Rietveld quantitative phase analysis results. The principal crystalline phases detected in all samples include quartz (Q), portlandite (P), gypsum (G), ettringite (E), calcium silicate hydrate (C–S–H), calcite (C), and belite (B). The presence of these same characteristic peaks in all specimens indicates that the incorporation of the filler material did not alter the nature of the main hydration products. This suggests that the filler behaved primarily as an inert phase within the cementitious matrix during early hydration. A clear distinction in the diffraction intensities of several phases becomes apparent as the replacement level increases. The portlandite peak at approximately 18° 2θ shows a gradual reduction in intensity, implying a lower CH content in mixtures with higher filler dosage. This reduction may be attributed to the dilution of the cement component or to partial consumption of portlandite during secondary reactions involving the filler. Conversely, the diffraction peak at around 29° 2θ, associated with calcite, becomes progressively more pronounced with increasing replacement content. This observation is consistent with the higher CaCO3 contribution from the filler and confirms the increasing calcite proportion detected by quantitative phase analysis.
The quantitative Rietveld results shown in Table 4 reinforce these trends. Quartz remains the predominant phase in all samples, varying slightly from 60.6% in the control mix to 58.1% in the 30% replacement mixture. The content of portlandite decreases from 9.8% in the control mix to 5.4% at 30% replacement, reflecting reduced hydration or dilution effects. In contrast, calcite shows a substantial increase from 5.8% to 25%, confirming the contribution of carbonate material from the filler. Minor variations are observed in the quantities of ettringite (5–10%) and gypsum (3–8%), while the relative content of C–S–H remains low (1–3%), which is typical given its poorly crystalline nature and the limited detection sensitivity of XRD. Belite is present in trace amounts (<1%) in all mixtures.
Overall, the XRD results demonstrate that the incorporation of filler primarily affects the relative proportions of existing crystalline phases rather than generating new hydration products. The observed decrease in portlandite and increase in calcite content with higher replacement levels indicate that the filler influences the hydration balance by modifying the available Ca(OH)2 and CaCO3 phases. Nevertheless, the consistent presence of ettringite and C–S–H across all mixes suggests that the fundamental hydration reactions of cement were not significantly impeded by the filler substitution.

5.7. Alkalinity Test

The chemical environment within concrete is strongly influenced by its pH level, which plays a critical role in determining durability and resistance to reinforcement corrosion. Freshly prepared concrete typically maintains a highly alkaline environment with a pH between 12 and 13, providing a protective passive layer around reinforcing steel. A reduction in alkalinity can destabilise this passive film, increase the risk of steel corrosion and compromise structural durability. Therefore, monitoring pH levels is essential for assessing the long-term performance of concrete. From the experimental results, the control mix (CM) exhibited a pH of 12.59, which falls within the expected range for normal concrete. When scallop seashell powder and fillers were incorporated, a gradual increase in alkalinity was observed, as shown in Figure 8. The S0F15 mix reached a pH of 12.67 (0.64% increase relative to CM), the S15F15 mix attained 12.71 (0.95% increase), and the maximum pH of 12.74 (1.19% increase) was observed for the S30F15 mix.
The increase in pH is primarily attributed to the high calcium carbonate (CaCO3) content of scallop seashells. During hydration, CaCO3 reacts with water and cement phases to release calcium hydroxide (Ca(OH)2), which maintains the high pH environment in the concrete. Additionally, minor trace elements present in scallop seashells, such as magnesium (Mg), sodium (Na), and iron (Fe), may contribute marginally by forming hydroxides or influencing the solubility of calcium hydroxide, thereby supporting the alkaline environment. The presence of silica in seashells can also undergo pozzolanic reactions, consuming some Ca(OH)2 to form additional calcium silicate hydrate (C–S–H), which refines the pore structure and improves strength. Overall, the combined effects of Ca(OH)2 and trace elements ensure that all tested mixes maintain pH values within the safe range of 12–13. This indicates that the use of scallop seashell powder does not compromise the protective alkalinity required to prevent reinforcement corrosion and may even help sustain the passivation layer around steel, enhancing the durability potential of the concrete.

5.8. Carbon Emissions

The research project investigates the potential utilisation of waste seashells as an additional binding material in concrete. To assess the environmental impact, carbon emissions associated with different concrete mixes were estimated using a simplified emobodied carbon approach. The methodology involved calculating emissions from raw materials, including cement, aggregates, and ground seashell powder (Section 4.4), as well as energy consumption during production. System boundaries were defined at the concrete production stage, and all calculations were based on a functional unit of 1 m3 of concrete. Providing this clear methodology ensures that the results are reproducible and scientifically valid.
The estimated carbon emissions for the different mixes are presented in Figure 9. Traditional concrete designed according to British standards produced 331 kg CO2 e/m3. Concrete with 15% and 30% seashell powder replacement (with an additional 15% cement replaced by powder acting as a filler in both cases) exhibited lower emissions of 250 and 212 kg CO2 e/m3, respectively, corresponding to reductions of approximately 24% and 36% compared to the control mix. These findings indicate that partial replacement of cement with seashell powder can reduce the environmental footprint of concrete without compromising its mechanical performance.

6. Conclusions

Experimental investigations were carried out to examine the utilisation of waste seashell powder as a filler material and partial cement replacement in concrete. The primary focus of the study was to assess the impact of seashell incorporation and the replacement rate of seashell powder in the concrete mixes on the carbon emissions reductions, compressive strength, stiffness, setting times, microstructure and hydration products. The key findings are summarised as follows:
  • The seashells were initially ground to a powder form, within the size range of 63–125 microns, which can be used as filler and 0–63 microns used as cement replacement material in conventional concrete. The key benefit is to utilise this recycled waste to reduce the carbon emissions of concrete without negatively affecting its performance. The cement was reduced by 15%, 30% and 45% (with seashell powder utilised as 15% filler, 15% filler + 15% cement replacement, and 15% filler + 30% cement replacement, respectively).
  • Utilising waste seashells facilitates the production of environmentally friendly concrete. Specifically, when compared to conventional concrete, incorporating seashells into the mix with 15% and 30% seashell powder content as cement replacement (plus 15% cement replaced with the powder acting as a filler in both cases), resulted in a notably lower carbon emission by about one quarter to one third, respectively.
  • The compressive strength of concrete with seashells was reduced as the fraction of seashell replacement increased. The compressive strength of different mix combinations displayed a moderate descending trend. The highest strength was observed in a mix without any partial replacement of cement with seashells, but with the inclusion of 15% seashell filler. This is almost the same value as that of the control mix. On the other hand, the mix featuring 30% partial replacement demonstrated ~25% reduction in strength over the control mix.
  • Experimental results from the tested concrete cylinders revealed that the Young’s modulus of elasticity of the seashell-powder-containing concrete mixes was moderately lower than the control mix counterpart. The reductions were about 5%, 7% and 13% for mixes S0F15, S15F15 and S30F15, respectively, compared to the control mix CM. These results suggest that the inclusion of seashells up to an optimum level does not drastically affect the stiffness properties of the resulting concrete material.
  • The bulk density of concrete reduces as the proportion of seashell insertion increases. This tendency shows that because seashells have a lower density than typical aggregates, they diminish the total density of the concrete. However, the decrease is very small, ranging from 0.99% to 2.27% of the control mix (as the percentage of partial replacement of cement and the filler effect of seashells increases).
  • The initial setting time showed a 30% increase compared to the control mix when seashells were added at a 30% partial replacement, while the final setting time decreased by about 12%. This is mainly due to the porous nature of seashells, which can absorb water and retards the hydration process in the early stage.
  • The microstructural analysis using the SEM analysis revealed denser microstructures with fewer microcracks and enhanced C–S–H gel formation in seashell-modified concretes, particularly in the S30F15 mix, indicating improved matrix densification and hydration. XRD analysis confirmed an increase in calcite and a reduction in portlandite content with higher seashell levels, signifying beneficial filler and secondary reaction effects that enhance structural compactness.
The findings confirm that ground seashell powder can be effectively utilised as a sustainable, low-carbon supplementary material in concrete production. While higher replacement levels (>30%) result in moderate strength loss, partial substitutions (up to 15%) combined with filler use offer an optimal balance between mechanical integrity and environmental benefit. Further research is recommended to evaluate long-term durability, hydration kinetics, and large-scale implementation of seashell-based concretes under various exposure conditions. This approach contributes to waste valorisation and the advancement of circular, eco-efficient construction materials.

Author Contributions

Conceptualization, A.A.; methodology, A.A. and A.K.; software, A.K.; validation, A.A. and A.K.; formal analysis, A.K.; investigation, A.A. and A.K.; resources, A.A.; data curation, A.K.; writing—original draft preparation, A.K.; writing—review and editing, A.A.; visualization, A.K.; supervision, A.A.; project administration, A.A.; funding acquisition, A.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was partially funded by the Institution of Structural Engineers (IStructE) MSc Research Grant 2023/24.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors would like to acknowledge the technical support provided by Chris Donovan of the University of East London Concrete Materials and Structures Laboratory.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Eziefula, U.G.; Ezeh, J.C.; Eziefula, B.I. Properties of seashell aggregate concrete: A review. Constr. Build. Mater. 2018, 192, 287–300. [Google Scholar] [CrossRef]
  2. Borrachero, M.V.; Payá, J.; Brito, S.; Segura, Y.P.; Soriano, L.; Tashima, M.M.; Monzó, J.M. Reusing Construction and DemolitionWaste to Prepare Alkali-Activated Cement. Materials 2022, 15, 3437. [Google Scholar] [CrossRef]
  3. Awoyera, P.O.; Adesina, A.; Gobinath, R. Role of recycling fine materials as filler for improving the performance of concrete—A review. Aust. J. Civ. Eng. 2019, 17, 85–95. [Google Scholar] [CrossRef]
  4. Kanavaris, F.; Gibbons, F.; Walport, E.; Shearer, E.; Abbas, A.A.; Orr, J.; Marsh, B. Reducing embodied carbon dioxide of structural concrete with lightweight aggregate. Proc. Inst. Civ. Eng. Eng. Sustain. 2022, 175, 75–83. [Google Scholar] [CrossRef]
  5. Abbas, A.; Mahadevan, M.; Prajapati, S.; Ayati, B.; Kanavaris, F. Development of low-carbon lightweight concrete using pumice as aggregate and cement replacement. In Proceedings of the RILEM International Conference on Synergising Expertise Towards Sustainability and Robustness of Cement-based Materials and Concrete Structures (SynerCrete’23), Milos, Greece, 14–16 June 2023; Springer: Cham, Switzerland, 2023. [Google Scholar] [CrossRef]
  6. Nasaeng, P.; Wongsa, A.; Cheerarot, R.; Sata, V.; Chindaprasirt, P. Strength enhancement of pumice-based geopolymer paste by incorporating recycled concrete and calcined oyster shell powders. Case Stud. Constr. Mater. 2022, 17, e01307. [Google Scholar] [CrossRef]
  7. Abbas, A.; Jabr, E. Experimental investigation of bio-concrete using eggshells as supplementary cementitious material. In Proceedings of the Concrete Solutions 2025—9th International Conference on Concrete Repair, Durability & Technology, MATEC Web of Conferences, Lisbon, Portugal, 16–18 June 2025; Volume 409, p. 13007. [Google Scholar] [CrossRef]
  8. Chen, J.J.; Ng, P.L.; Li, B.H.; Kwan, A.K.H. Concurrent paste replacement and aggregate replacement strategy for producing eco-efficient and low-carbon concrete. Clean. Technol. Environ. Policy 2022, 24, 2459–2477. [Google Scholar] [CrossRef]
  9. Kang, S.H.; Hong, S.G.; Moon, J. The use of rice husk ash as reactive filler in ultra-high performance concrete. Cem. Concr. Res. 2019, 115, 389–400. [Google Scholar] [CrossRef]
  10. Zhu, Y.; Chen, D.; Yu, X.; Liu, R.; Liao, Y. Properties of Cementitious Materials Utilizing Seashells as Aggregate or Cement: Prospects and Challenges. Materials 2024, 17, 1222. [Google Scholar] [CrossRef]
  11. Ephraim, M.E.; ThankGod, O.; Gbinu, K.S. Performance of high Strength Concrete Using Oyster Shell Ash as Partial Replacement for Cement. SSRG Int. J. Civ. Eng. 2019, 6, 33–38. [Google Scholar] [CrossRef]
  12. González-Caro, Á.; Merino-Lechuga, A.M.; Fernández-Ledesma, E.; Fernández-Rodríguez, J.M.; Jiménez, J.R.; Suescum-Morales, D. The Effect of Acanthocardia tuberculata Shell Powder as Filler on the Performance of Self-Compacting Mortar. Materials 2023, 16, 1734. [Google Scholar] [CrossRef]
  13. Magnabosco, G.; Giuri, D.; Di Bisceglie, A.P.; Scarpino, F.; Fermani, S.; Tomasini, C.; Falini, G. New material perspective for waste seashells by covalent functionalization. ACS Sustain. Chem. Eng. 2021, 9, 6203–6208. [Google Scholar] [CrossRef]
  14. Joseph, O.O. Evaluation of the properties of lightweight concrete using periwinkle shells as a partial replacement for coarse aggregate. J. Appl. Sci. Environ. Manag. 2016, 20, 497–505. [Google Scholar] [CrossRef]
  15. Orangun, C.O. The suitability of periwinkle shells as coarse aggregate for structural concrete. Mater. Constr. 1974, 7, 341–346. [Google Scholar] [CrossRef]
  16. Liao, Y.; Fan, J.; Li, R.; Da, B.; Chen, D.; Zhang, Y. Influence of the usage of waste oyster shell powder on mechanical properties and durability of mortar. Adv. Powder Technol. 2020, 23, 103503. [Google Scholar] [CrossRef]
  17. Silva, A.L.d.; Kohlman Rabbani, E.R.; Shakouri, M. Seashell Powder as a Sustainable Alternative in Cement-Based Materials: A Systematic Literature Review. Sustainability 2025, 17, 592. [Google Scholar] [CrossRef]
  18. Jasni, S.A.; Muthusamy, K.; Ruslan, H.N.; Hamada, H.M.; Ab Wahab, E.S. Use of Seashell as Cement Replacement in Construction Material: A Review. Construction 2024, 4, 7–20. [Google Scholar] [CrossRef]
  19. Hasan, K.; Karim, A.; Islam, M.T.; Ali, M.B.; Rahman, M.T.; Rahman, M.M.; Yahaya, F.M. A review of the mechanical properties and durability of concrete containing recycled seashells as a partial cement replacement. J. Mater. Cycles Waste Manag. 2023, 25, 3192–3216. [Google Scholar] [CrossRef]
  20. Abbas, A.; Abdalla, K.; Saji, G. Experimental investigation of seashell concrete with anti-corrosion agent enhancement. In Proceedings of the Concrete Solutions 2025—9th International Conference on Concrete Repair, Durability & Technology, MATEC Web of Conferences, Lisbon, Portugal, 16–18 June 2025; Volume 409, p. 14003. [Google Scholar] [CrossRef]
  21. Abbas, A.; Abdalla, K.; Sidgel, A. Self-healing of concrete incorporating seashells as partial cement replacement. In Proceedings of the Concrete Solutions 2025—9th International Conference on Concrete Repair, Durability & Technology, MATEC Web of Conferences, Lisbon, Portugal, 16–18 June 2025; Volume 409, p. 14004. [Google Scholar] [CrossRef]
  22. Bamigboye, G.; Enabulele, D.; Odetoyan, A.O.; Kareem, M.A.; Nworgu, A.; Bassey, D. Mechanical and durability assessment of concrete containing seashells: A review. Cogent Eng. 2021, 8, 1883830. [Google Scholar] [CrossRef]
  23. Nukah, P.D.; Abbey, S.J.; Booth, C.A.; Nounu, G. Optimisation of embodied carbon and compressive strength in low-carbon concrete. Materials 2022, 15, 8673. [Google Scholar] [CrossRef]
  24. Bamigboye, G.O.; Nworgu, A.T.; Odetoyan, A.O.; Kareem, M.; Enabulele, D.O.; Bassey, D.E. Sustainable use of seashells as binder in concrete production: Prospect and challenges. J. Build. Eng. 2021, 34, 101864. [Google Scholar] [CrossRef]
  25. Leman, A.S.; Shahidan, S.; Nasir, A.J.; Senin, M.S.; Mohd Zuki, S.S.; Wan Ibrahim, M.H.; Deraman, R.; Khalid, F.S.; Azhar, A.T.S. Properties of concrete containing coconut shell powder (CSP) as a filler. IOP Conf. Ser. Mater. Sci. Eng. 2017, 271, 012006. [Google Scholar] [CrossRef]
  26. Wang, J.; Liu, E.; Li, L. Characterization on the recycling of waste seashells with Portland cement towards sustainable cementitious materials. J. Clean. Prod. 2019, 220, 235–252. [Google Scholar] [CrossRef]
  27. Bamigboye, G.O.; Okechukwu, U.E.; Olukanni, D.O.; Bassey, D.E.; Okorie, U.E.; Adebesin, J.; Jolayemi, K.J. An effective economic combination of waste seashell and river sand as fine aggregate in green concrete. Sustainability 2022, 14, 12822. [Google Scholar] [CrossRef]
  28. Othman, N.H.; Bakar, B.H.A.; Don, M.M.; Johari, M.A.M. Cockle shell ash replacement for cement and filler in concrete. Malays. J. Civ. Eng. 2013, 25, 201–211. [Google Scholar] [CrossRef]
  29. Anagnostopoulos, N.; Sideris, K.K.; Georgiadis, A. Mechanical characteristics of self-compacting concretes with different filler materials, exposed to elevated temperatures. Mater. Struct. 2009, 42, 1393–1405. [Google Scholar] [CrossRef]
  30. Galan, I.; Briendl, L.; Thumann, M.; Steindl, F.; Röck, R.; Kusterle, W.; Mittermayr, F. Filler effect in shotcrete. Materials 2019, 12, 3221. [Google Scholar] [CrossRef]
  31. Liao, Y.; Shi, H.; Zhang, S.; Da, B.; Chen, D. Particle size effect of oyster shell on mortar: Experimental investigation and modelling. Materials 2021, 14, 6813. [Google Scholar] [CrossRef]
  32. BS EN 206:2013+A2:2021; Concrete. Specification, Performance, Production and Conformity. British Standards Institution: London, UK, 2021. [CrossRef]
  33. Teychenné, D.C.; Franklin, R.E.; Erntroy, H.C. Design of Normal Concrete Mixes, 2nd ed.; BRE Report BR 331; Building Research Establishment (BRE): Garston, Watford, UK, 1997; ISBN 978-1-86081-172-2. [Google Scholar]
  34. BS EN 12350-2:2019; Testing Fresh Concrete—Slump Test. British Standards Institution: London, UK, 2019. [CrossRef]
  35. Nowtricity. Current Emissions in the United Kingdom. CO2 Emissions per kWh in United Kingdom—Nowtricity. Available online: https://www.nowtricity.com/country/united-kingdom/ (accessed on 13 March 2025).
  36. Gibbons, O.P.; Orr, J.J.; Archer-Jones, C.; Arnold, W.; Green, C. How to Calculate Embodied Carbon, 2nd ed.; Institution of Structural Engineers (IStructE): London, UK, 2022. [Google Scholar]
  37. Kim, J.; Cha, I.; Jo, B.; Lee, H. Evaluation of compressive strength of eco-friendly cementitious composites incorporating waste oyster shells under sodium chloride solution exposure. Case Stud. Constr. Mater. 2025, 23, e04944. [Google Scholar] [CrossRef]
  38. BS EN 197-1:2011; Cement—Composition, Specifications and Conformity Criteria for Common Cements. British Standards Institution: London, UK, 2019.
  39. Eisa, M.S.; Basiouny, M.E.; Youssef, A.M. Effect of using various waste materials as mineral filler on the properties of the asphalt mix. Innov. Infrastruct. Solut. 2018, 3, 29. [Google Scholar] [CrossRef]
  40. BS EN 12390-13:2021; Testing Hardened Concrete—Determination of Secant Modulus of Elasticity in Compression. British Standards Institution: London, UK, 2021. [CrossRef]
  41. Nduka, D.O.; Akanbi, E.T.; Ojo, D.O.; Babayemi, T.E.; Jolayemi, K.J. Investigation of the mechanical and microstructural properties of masonry mortar made with seashell particles. Materials 2023, 16, 2471. [Google Scholar] [CrossRef]
  42. Zhou, M.; Chen, J.; Huang, W.; Chao, H.; Yu, L.; Ma, X.; Ouyang, X. Multiscale study on the effect of Seashell powder on rheology, hydration and strength development of cement paste. Constr. Build. Mater. 2024, 456, 139257. [Google Scholar] [CrossRef]
  43. Chung, S.Y.; Oh, S.E.; Jo, S.S.; Lehmann, C.; Won, J.; Elrahman, M.A. Microstructural investigation of mortars incorporating cockle shell and waste fishing net. Case Stud. Constr. Mater. 2023, 18, e01719. [Google Scholar] [CrossRef]
  44. Mehta, P.K.; Monteiro, P.J.M. Concrete: Microstructure, Properties, and Materials, 4th ed.; McGraw-Hill Professional: New York, NY, USA, 2014; ISBN 9780071797870. [Google Scholar]
Constrmater 05 00082 g001
Figure 1. Particle size Distribution Curve of materials.
Figure 1. Particle size Distribution Curve of materials.
Constrmater 05 00082 g001
Constrmater 05 00082 g002
Figure 2. Bulk Density of Concrete Mix and the deviation of mixes from the control mix.
Figure 2. Bulk Density of Concrete Mix and the deviation of mixes from the control mix.
Constrmater 05 00082 g002
Constrmater 05 00082 g003
Figure 3. Initial and Final setting time of Concrete mixes and the deviation of mixes from the control mix.
Figure 3. Initial and Final setting time of Concrete mixes and the deviation of mixes from the control mix.
Constrmater 05 00082 g003
Constrmater 05 00082 g004
Figure 4. Compressive strength of concrete mixes and the percentage deviation from the Control mix.
Figure 4. Compressive strength of concrete mixes and the percentage deviation from the Control mix.
Constrmater 05 00082 g004
Constrmater 05 00082 g005
Figure 5. Modulus of Elasticity of concrete mixes and the percentage deviation from the Control mix.
Figure 5. Modulus of Elasticity of concrete mixes and the percentage deviation from the Control mix.
Constrmater 05 00082 g005
Constrmater 05 00082 g006
Figure 6. SEM images of different Concrete mixes (a) Control mix, (b) Filler mix with 0% Replacement (S0F15) and (c) Filler mix with 30% Replacement (S30F15).
Figure 6. SEM images of different Concrete mixes (a) Control mix, (b) Filler mix with 0% Replacement (S0F15) and (c) Filler mix with 30% Replacement (S30F15).
Constrmater 05 00082 g006
Constrmater 05 00082 g007
Figure 7. Results of XRD Analysis of Different Concrete Mixes at 28 days.
Figure 7. Results of XRD Analysis of Different Concrete Mixes at 28 days.
Constrmater 05 00082 g007
Constrmater 05 00082 g008
Figure 8. Alkalinity pH values of different Concrete mixes and the percentage deviation from the control mix.
Figure 8. Alkalinity pH values of different Concrete mixes and the percentage deviation from the control mix.
Constrmater 05 00082 g008
Constrmater 05 00082 g009
Figure 9. Carbon Emission from different concrete mixes and the percentage deviation from the Control mix.
Figure 9. Carbon Emission from different concrete mixes and the percentage deviation from the Control mix.
Constrmater 05 00082 g009
Table 1. Specific Gravity and Water Absorption.
Table 1. Specific Gravity and Water Absorption.
Type of MaterialSpecific
Gravity		Water
Absorption (%)
Fine Aggregate2.377.06
Coarse
Aggregate (5–10 mm)		3.000.68
Coarse
Aggregate
(10–20 mm)		2.560.53
Seashell Powder2.381.42
Table 2. Mix Design Table (kg/m3).
Table 2. Mix Design Table (kg/m3).
Materials Control MixS0F15S15F15S30F15
Cement Content *350300255210
Seashell-Cement Replacement0045 (15%)90 (30%)
Seashell-Filler 050 (15%)50 (15%)50 (15%)
Water Content 160160.75161.43162.10
Coarse Aggregate (10–20 mm) 925925925925
Coarse Aggregate
(5–10 mm) 		465465465465
Fine Aggregate (<5 mm)510510510510
* Combined cement replacement (using seashell powder as filler and finer material) is 15%, 30% and 45%.
Table 3. Carbon Emission factors for materials used.
Table 3. Carbon Emission factors for materials used.
Type of MaterialEmission Factor
Cement0.91 [36]
Water0.000344 [36]
Fine Aggregate0.004 [36]
Coarse Aggregate 0.00747 [36]
Seashell Powder0.059 (new proposed value)
Table 4. Quantitative phase composition (wt.%) of Mixes at 28 days by Rietveld refinement.
Table 4. Quantitative phase composition (wt.%) of Mixes at 28 days by Rietveld refinement.
PhaseControl Mix S0F15S15F15S30F15
Quartz60.668.057.958.1
Portlandite9.86.16.35.4
Gypsum 7.64.42.92.8
Ettringite 10.45.75.76.9
C-S-H2.62.71.01.3
Calcite 5.810.618.225.0
Belite 0.80.51.10.1
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Abbas, A.; Kudukkan, A. Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement. Constr. Mater. 2025, 5, 82. https://doi.org/10.3390/constrmater5040082

AMA Style

Abbas A, Kudukkan A. Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement. Construction Materials. 2025; 5(4):82. https://doi.org/10.3390/constrmater5040082

Chicago/Turabian Style

Abbas, Ali, and Anjana Kudukkan. 2025. "Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement" Construction Materials 5, no. 4: 82. https://doi.org/10.3390/constrmater5040082

APA Style

Abbas, A., & Kudukkan, A. (2025). Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement. Construction Materials, 5(4), 82. https://doi.org/10.3390/constrmater5040082

Article Metrics

Back to TopTop