Search Results (30)

Autoclaved Aerated Concrete (AAC) is a lightweight, thermally insulating, and fire-resistant building material that has become prominent in sustainable construction due to its reduced production energy demands and minimal environmental impact. As an increasing number of AAC-based structures reach end-of-life, the effective recycling and reuse of AAC waste present both challenges and opportunities within the context of sustainable building practices and circular economy frameworks. This study presents a scientometric review of AAC recycling research published between 2014 and 2024, using the Web of Science database and bibliometric tools such as CiteSpace. Key trends, techniques, and knowledge gaps in AAC recycling are identified, highlighting issues such as high energy consumption, limited practical implementation, and the absence of standardized recovery protocols. The study also outlines emerging research pathways, including detailed material characterization, development of recycling standards, innovative reuse techniques, hybrid material systems, and the integration of recycled AAC in new construction. These insights provide a foundation for advancing sustainable building material strategies and inform policy and practice in construction waste management. Full article

The use of mineral waste for the production of lightweight artificial aggregate is an important element of activities for sustainable development in construction and the implementation of the objectives of the circular economy. The article presents the physical, mechanical, and ecological properties of an innovative artificial aggregate produced from bottom sediments, concrete dust, and municipal solid waste incineration fly ash. The obtained research results confirm that the developed material achieves technological properties comparable to artificial aggregates available on the market, both commercial and those derived from recycling. However, the increased leachability of chlorides and sulphates remains a significant challenge, which may limit the scope of its applications. Despite this, the material shows the potential for use, among others, in the production of lightweight concrete. The analyses carried out have shown that the thermal hardening processes (200–400 °C) and autoclaving do not guarantee full immobilization of harmful substances contained in the raw materials for the production of this type of aggregate. Full article

Non-autoclaved aerated concrete (NAAC) is gaining attention for its strength-to-weight ratio and sustainability benefits. Produced by incorporating a blowing agent into a binder, aggregate, and water mixture, NAAC offers a lightweight and porous construction material. Ash and slag waste (ASW), primarily composed of silicon, aluminum, iron, and calcium oxides, presents significant potential as a sustainable additive. However, industrial-scale processing of ASW still needs to be explored in Kazakhstan. This study evaluates the feasibility of utilizing ASW from the Ust-Kamenogorsk Thermal Power Plant to produce earthquake-resistant NAAC. Incorporating 31.5% ASW by weight optimizes compressive strength, achieving 2.35 MPa and significantly improving the mechanical properties. Chemical and microstructural analyses confirm ASW’s suitability as a construction material. The study also introduces innovative processing methods and explores convolutional neural network models for predicting material structure changes, providing insights into optimizing production processes. The findings address the research objectives by confirming the viability of ASW in NAAC production and demonstrating its potential for sustainable construction. The results offer a pathway for industrial-scale applications, contributing to waste utilization and resource conservation. Full article

Non-sintered lightweight aggregate (NSLA) produced by pelletizing and autoclaved curing has received widespread attention due to its environmental protection. However, the effect law of its characteristics, such as particle gradation and water absorption, on the performance of concrete still lacks clear understanding. In this study, seven different gradation types of concrete were designed to investigate the influence of the particle gradation (particularly particle size) of NSLA on the mechanical properties, especially the axial compressive performance, of alkali-activated slag non-sintered lightweight aggregate concrete (AN-LAC). Meanwhile, the different pre-treatment methods for NSLA were also studied to reduce the drying shrinkage of AN-LAC caused by the high water absorption of NSLA. The results showed that the compressive strength, splitting tensile strength, and flexural strength of AN-LAC at 3 d, 7 d, and 28 d showed an increasing trend when the average particle size decreased. The compressive strength of AN-LAC containing 3~5 and 6~10 mm NSLA at 28 days reached the maximum value of 56.7 MPa. AN-LAC containing NSLA with a small particle size exhibited improved elastic modulus. And the modified elastic modulus prediction model of AN-LAC was established considering the effect of particle size of NSLA. The NSLA, which was modified by using a silicone hydrophobic agent and pre-wetted by soaking in water, respectively, could enhance the strength of AN-LAC at 28 days. Combined with the analysis of the microscopic morphology of the ITZ, the shrinkage rate of the concrete with pre-wetted NSLA and modified NSLA at 90 days decreased by 17.7% and 10.3%, respectively. Full article

Cellular materials such as aluminum and polyurethane foams are recognized for their effectiveness in energy absorption. They commonly serve as crushable cores in sacrificial cladding for blast mitigation purposes. This study delves into the effectiveness of autoclaved aerated concrete (AAC), a lightweight, porous material known for its energy-absorbing properties as a crushable core in sacrificial cladding. The experimental set-up features a rigid frame made of steel measuring 1000 × 1000 × 15 mm³ with a central square opening (300 × 300 mm²) holding a 2 mm thick aluminum plate representing the structure. The dynamic response of the aluminum plate is captured using two high-speed cameras arranged in a stereoscopic configuration. Three-dimensional digital image correlation is used to compute the transient deformation fields. Blast loading is achieved by detonating 20 g of C4 explosive set at 250 mm from the plate’s center. The study assesses the mineral foam’s absorption capacity by comparing out-of-plane displacement and mean permanent deformation of the aluminum plate with and without the protective solution. Six foam configurations (A to F) are tested experimentally and numerically, varying in the foam’s free space for expansion relative to its total volume. Results show positive protective effects, with configuration F reducing maximum deflection by at least 30% and configuration C by up to 70%. Foam configuration influences energy dissipation, with an optimal lateral surface-to-volume ratio (ζ) enhancing protective effects, although excessive ζ leads to non-uniform foam crushing. To address the influence of front skin deformability, a non-deformable front skin has been adopted. The latter demonstrates an increased effectiveness of the sacrificial cladding, particularly for ζ values above the optimal value obtained when using a deformable front skin. Notably, using a non-deformable front skin increases maximum deflection reduction and foam energy absorption by up to approximately 30%. Full article

Autoclaved aerated concrete (AAC) has gained widespread acceptance in construction as a lightweight solution for exterior and interior walls. However, traditional steel-reinforced autoclaved aerated concrete (SR-AAC) has limitations, including concerns over its ductility and difficulty in cutting during installation. The steel reinforcement also has high embodied carbon that does not align with the actions in the construction section to reach carbon neutrality shortly. This study investigated the material properties and mechanical performances of factory-produced fiber-reinforced autoclaved aerated concrete (FR-AAC) panels, aiming to examine their potential as an alternative solution. Full-scale FR-AAC panels with thicknesses of 100 mm, 150 mm, and 200 mm were manufactured and tested. Some panels were down-sampled to determine the dry density, water absorption, compressive strength, and flexural strength of the material, while the mechanical performances were evaluated through static and impact loading tests. The results showed that the average dry density and absorption of the FR-AAC material are 533 kg/m³ and 63%, respectively, with compressive strengths up to 3.79 MPa and flexural strengths reaching 0.97 MPa. All six panels tested under static uniformly distributed loading exceeded the self-weight limit by a factor of 1.5, satisfying standard requirements for load-bearing capacity. However, the brittle failure modes observed in some tests raise potential health and safety concerns. In contrast, the impact tests revealed that the panels have acceptable performances with the inclusion of fibers. Full article

Rice husk (RH) and straw are common agricultural wastes in Asian countries, and they are potential bioresources for building materials. RH contains a large amount of SiO₂, and many studies have burnt RH to ash and then used it as a silica supplement in cement and concrete. However, the combustion of RH has an additional cost and exacerbates CO₂ emissions and air pollution. RH inherently has a low bulk density and porous structure; therefore, it should be possible to directly use RH as a lightweight additive in concrete. The purposes of this study were to use RH in the production of autoclaved lightweight concrete (ALC) and to examine the effects of RH on ALC properties. Four RHs with different particle sizes, i.e., >1.2 mm, 0.6–1.2 mm, 0.3–0.6 mm, and <0.3 mm, were used as lightweight additives, and the ALC specimens were prepared with 0–20 wt.% RHs by autoclaving at 189 °C for 12 h. The >0.3 mm RH was applicable to prepare the ALC specimens, and the decomposition effect of <0.3 mm RH was significant. Both the bulk density and the compressive strength of the ALC specimens decreased with increasing RH size. RH with a particle size larger than 1.2 mm seems more appropriate for ALC production than RH with a smaller particle size because of the lower bulk density and higher compressive strength. The Ca/Si ratio decreased with increasing RH size, which affected the formation of tobermorite and thus reduced the compressive strength of the ALC specimens. With a suitable water-to-solid (W/S) ratio, the use of RHs as lightweight additives can yield ALC specimens that meet the requirements of commercial products. Full article

The sudden collapse of a school roof in the UK brought widespread attention to the structural integrity of buildings constructed with reinforced autoclaved aerated concrete (RAAC), a material widely used from the 1950s to the mid-1990s. RAAC, known for its lightweight and insulating properties, has been found to suffer from weak compressive strength, poor reinforcement anchorage, and high susceptibility to environmental degradation. The structural profiles of RAAC panels in the UK are unique, particularly in their reinforcement configurations and failure modes, which limits the applicability of the existing literature from other regions. This paper conducts a state-of-the-art review, identifying a significant gap in current research due to the unique challenges posed by RAAC in the UK, and highlights the need for novel methodologies. In response to this gap, the paper introduces a multi-criteria decision analysis (MCDA) framework utilising the decision-making trial and evaluation laboratory (DEMATEL) method to assess the interdependencies of RAAC defects. This methodology quantifies the influence of observed defects and guides the selection of appropriate remediation strategies, offering a more structured and objective approach to RAAC panel assessment and retrofitting. Practically, this study aligns with ongoing research efforts towards the digitalisation of RAAC management by integrating the MCDA model within digital asset management systems. This integration supports a holistic approach to addressing the RAAC crisis, enhancing current efforts to digitalise the surveying and management processes and ensuring safer long-term solutions. Full article

It is most effective to reduce floor impact noise as close to the sound source as possible. In apartments, there are multiple layers in the floor system, from floor finishing to the structural concrete slab. Apart from the floor finishing, mortar lies at the top layer of the floor system, followed by autoclaved lightweight concrete, insulation, and the concrete slab. The present study aims to identify the reduction characteristics of light and heavy floor impact noises by changing the glass transition temperature of an SBR (styrene–butadiene rubber) latex mortar. To achieve this, structural tests were undertaken to find the appropriate mix proportions of SBR latex in the mortar, meeting the glass transition temperature based on the physical test results regarding the latex mortar. As seen in the study method and process, because this study aimed to both increase and decrease the strength compared to general mortar, a 7% mixture ratio of Tg 4 °C SBR latex was decided upon for the strength increase, while a 5% mixture ratio of Tg −16 °C SBR latex was chosen for the strength reduction. A mock-up specimen was created using the SBR latex-modified mortar according to the identified mix proportions, and the characteristics of light- and heavy-weight floor impact noises of the SBR latex-modified mortar were then examined. Comprehensive analysis of the reduction performance of the floor impact noise revealed that the Tg −16 °C SBR latex-mixed mortar showed a reduction effect of about 2–5 dB for light-weight impact noise and about 7–10 dB for heavy-weight impact noise. Full article

The aim of this study was to evaluate the impact of service conditions on lightweight partitions in residential buildingsusing life-cycle assessments (LCAs). Three alternative service conditions were included as follows: light/moderate, standard, and intensive. LCAs were conducted for pairwise comparisons among three types of lightweight partitions: gypsum board, autoclaved aerated blocks, and hollow concrete blocks. The functional unit considered was 1 m² of a partition, and the building’s lifespan was 50 years. In light/moderate conditions, the replacement rate for all three partitions was zero times during the building’s lifespan. In standard conditions, the replacement rate for gypsum board and autoclaved aerated blocks was one time during the building’s lifespan, and for hollow concrete blocks, it was zero times. In intensive conditions, the replacement rate for gypsum board was four times during the building’s lifespan, that for autoclaved aerated blocks was two times, and that for hollow concrete blocks was zero times. The six ReCiPe2016 methodological options were used to estimate environmental damage using a two-stage nested analysis of variance. The results showed that, in light/moderate and standard conditions, gypsum board was the best alternative, while in intensive conditions, hollow concrete blocks were the best alternative. In conclusion, the choice of lightweight partitions should be made while taking the service conditions in residential buildings into account. Full article

Prefabricated panel-assembled wall systems, comprising a confining frame and infill lightweight panels of autoclaved aerated concrete (AAC), are widely employed in framed structures. Different from studies on a main frame with infill walls, this study aimed to explore the seismic performance of partition walls, which were fabricated with AAC panel-assembled walls and located outside of the main frames. Two full-scale specimens, one with a door opening and the other without, were constructed and cyclic loading tests were executed to examine the failure modes, hysteresis characteristics, envelope curves, ductility, strength and stiffness degradation, as well as energy dissipation capacity of the AAC panel-assembled walls. Additionally, a restoring-force model for the panel-assembled walls was developed and a method for predicting the lateral load-bearing capacity of the AAC panel-assembled walls was proposed. The findings indicated that the panels enhanced the system’s lateral resistance, energy dissipation capacity, and deformation capability. The door frame increased the initial stiffness, peak lateral load and energy dissipation capacity of the AAC panel-assembled wall compared to the wall without a door frame. Compared to the specimen without a door frame, the peak lateral load of the specimen with a door frame increased by 19.7–30.1%. The deformation capacity of the panel-assembled walls aligned with the requirements for concrete framed structures. Full article

The vast majority of different waste building units have negative environmental impacts around the world. Crushed building units can be recycled and utilized in the concrete industry to solve these problems and maintain natural resources. This study investigated the feasibility of employing crushed autoclaved aerated concrete (CAAC) and crushed clay brick (CCB) as a lightweight aggregate (LWA) to fabricate environmentally friendly recycled lightweight concrete (LWC). In addition, a lightweight expanded clay aggregate (LECA) was also used as an LWA, namely to study how the high porosity of an LWA can adversely affect the properties of LWC. Through the experimental program, all types of LWAs were pre-treated and strengthened with two cementitious grouts, and then the performance of the produced LWC was assessed by determining the slump of fresh concrete, the dry density, the unconfined compressive strength, and the splitting tensile strength at ages of 3, 7, 28, and 56 days. The laboratory results revealed that both CCB and CAAC can be reused as full substitutions for normal-weight coarse aggregate to manufacture LWC with appropriate properties. The obtained data show that the properties of an LECA, CCB, and CAAC were improved, and the porous structure can be strengthened by pre-treatment and coating with grouts. In the same way, the mechanical performance of produced LWC is also enhanced. Full article

The production of autoclaved aerated concrete via the autoclaving process incurs substantial energy consumption, posing a challenge to sustainable economic development. Herein, a novel nonautoclaved aerated concrete (NAAC) was prepared using sulfoaluminate cement as the primary raw material and aluminum powder as the aerating agent. The physicomechanical characteristics and pore structures of the sulfoaluminate-cement-based (SAC) NAAC (SAC-NAAC) were examined through X-ray diffraction, thermogravimetry, and scanning electron microscopy. The findings revealed that the optimal mechanical attributes of the SAC-NAAC were achieved at a water–cement ratio of 0.55, with a specific content ratio of polycarboxylate superplasticizer–borax–calcium stearate–sodium hydroxide at 0.24%:0.32%:0.36%:2.90%, along with 0.40% aluminum powder. The SAC-NAAC samples, with a bulk density range of 600–750 g/m³, exhibited a compressive strength of 3.55–4.16 MPa, porosity of 45.9–63.5%, and water absorption rate of 60.2–74.4%. The weight loss in the SAC-NAAC with different aluminum powder contents ranged between 15.23% and 16.83%. The prismatic ettringite (AFt) crystals served as the main source of strength for the SAC-NAAC, and AH₃ was attached to the AFt surfaces in a microcrystalline gel phase, thereby further enhancing the strength of the SAC-NAAC. Thus, the lightweight, high-strength SAC-NAAC has great potential as a nonautoclaved aerated concrete. Full article

This study investigates the life expectancy (LE) and life cycle costs (LCC) of three alternatives of interior partitions in residential units: gypsum board, autoclaved concrete block, and hollow concrete block partitions. The aim is to examine the sustainability and cost-effectiveness of these partitions in various service and occupancy conditions. Three different service conditions were analyzed: Standard (constructed without faults), Inherent Defect Conditions (with initial, non-progressing defects), and Failure Conditions (developing defects over time). To analyze the impact of occupancy conditions, six ‘negative occupancy factors’ were identified that accelerate partition deterioration, including non-ownership, poor maintenance, high residential density, the presence of young children, the presence of domestic animals, and the density of furniture. These factors define four occupancy condition categories: light, moderate, standard, and intensive. The research found that hollow concrete block partitions are the most durable, exceeding 100 years in light or moderate conditions. Gypsum board partitions, while cost-effective, have a lower life expectancy, needing replacement in 11–27 years in intensive conditions. Autoclaved concrete blocks offer moderate durability, with similar costs to hollow blocks in normal conditions. Overall, the study highlights the influence of service and occupancy on the lifespan of interior building components, and provides recommendations for partition type selection that are based on specific conditions. These recommendations are a pivotal outcome, highlighting the study’s significant contribution to the understanding of the long-term performance and sustainability of building materials in residential construction. Full article

The use of waste in the production of building materials is one of the possible ways to solve problems related to the sustainable management of non-degradable waste and difficult-to-recycle secondary resources. In this paper, a method is proposed for the non-autoclave production of an ultra-lightweight cellular concrete based on Portland cement, glass waste and liquid glass. A mixture of sodium hexafluorosilicate and hydroxide is used as a hardening activator, an aluminum powder serves as a gas-forming agent. The setting and hardening of raw mixtures occurs under the action of exothermal heat release due to a complex of chemical reactions occurring in the system, and the resulting material does not require additional heat treatment. It is optimal to use two fractions of glass waste to achieve acceptable material strength: coarse crushed (fineness modulus F_m = 0.945) and finely ground (specific surface S_sp = 450–550 m²/kg) glass. Glass particles of the fine fraction of glass, along with Portland cement, participate in hydrolytic and structure-forming processes, while glass particles of the coarse fraction play the role of reinforcing filler. The influence of the dispersion of glass and the density of liquid glass on the density, porosity, strength, water absorption and water resistance of the resulting cellular material was determined. At an average density of cellular concrete in the dry state of 150–320 kg/m³, the following characteristics can be achieved: a compressive strength up to 2.0 MPa, bending strength up to 0.38 MPa, thermal conductivity coefficient of the material in the range 0.05–0.09 W/(K·m), and a maximum operating temperature of 800 °C. The proposed ultra-lightweight cellular concrete can be used as a non-combustible heat and sound insulation material, as well as a repairing composition; the cellular concrete blocks can be used as filling masonry and for the construction of non-bearing internal walls. Full article