Search Results (349)

The transition towards carbon-neutral construction materials requires innovative solutions that combine reduced embodied energy, enhanced durability and improved building energy efficiency. This study investigates and compares two novel bioaerated low-density composites—BAAC and BIOAERMAC—developed through biologically driven aeration processes incorporating industrial byproducts. BAAC is produced using Saccharomyces cerevisiae and hydrogen peroxide, replacing conventional aluminum powder and improving safety while enabling the valorization of waste-derived yeast. BIOAERMAC is a gypsum-based composite incorporating synthetic anhydrite, microorganisms, peroxides, and recycled rubber from end-of-life tires. The materials were characterized in terms of hygrothermal behavior and dimensional stability, and compared with commercial autoclaved aerated concrete under equivalent mechanical strength conditions. The results highlight significant differences in moisture transport and shrinkage, primarily governed by pore structure and connectivity. BAAC exhibits behavior comparable to conventional AAC, whereas BIOAERMAC shows reduced capillary and hygroscopic absorption, indicating limited pore connectivity, but higher drying shrinkage. These findings demonstrate the effectiveness of bioaeration in tailoring pore structure and controlling the trade-off between moisture transport, durability, and dimensional stability, highlighting the potential of bioaerated composites for low-carbon and energy-efficient building applications. Full article

The utilization of construction and demolition waste (CDW) as a supplementary cementitious material (SCM) represents a promising strategy for reducing cement consumption, minimizing environmental impacts, and promoting sustainable waste valorization. In this study, hybrid recycled powder was produced from mixed CDW obtained from a Portuguese recycling facility and processed through mechanical grinding to achieve particle size characteristics comparable to Portland cement. The ground powder was subsequently thermally activated at 600 °C and evaluated as a partial replacement for Portland cement in concrete. Concrete mixtures were prepared with recycled powder replacement contents of 5%, 15%, 25%, and 35%. The physical, mechanical, and durability properties of the concrete were investigated, including density, water absorption, compressive strength, carbonation and chloride penetration resistance. The results indicate that thermally activated recycled powder can be successfully incorporated as a partial cement replacement while maintaining satisfactory mechanical and durability performance. These findings demonstrate that thermally activated hybrid recycled powder derived from mixed CDW has significant potential as a sustainable SCM, contributing to reduced cement consumption and supporting the development of low-carbon concrete. Full article

The article presents the results of experimental studies on the possibility of predicting the efficiency of CO₂ mineralization using metallurgical wastes (MWs) from the perspective of chemical thermodynamics and on identifying, accordingly, promising MWs for the production of construction materials and products. The study examined MWs from major Russian iron and steel producers, namely: blast furnace, electric steelmaking, ferroalloy, converter steelmaking slag, as well as nepheline slag, a by-product of nepheline ore processing for alumina. The CO₂ binding capacity of MWs was determined using experimental samples fabricated by semi-dry pressing of MW powders, followed by curing them in a gas atmosphere with an CO₂ concentration of 80% vol. It was found that the investigated MWs are capable of absorbing and binding CO₂, thereby improving their physical and mechanical properties. Experimental samples made from nepheline slag bind 11.3 to 12.0 wt.% of CO₂; samples from steelmaking slags: up to 9 wt.% or more; and samples from blast furnace dump slag: approximately 5.5 wt.% At the same time, the compressive strength of samples from steelmaking slags exceeds 100 MPa, that of samples from nepheline slag approaches 80 MPa, and that of samples from blast furnace dump slag exceeds 50 MPa. It has been established that predicting the efficiency of CO₂ mineralization by metallurgical wastes based solely on chemical thermodynamics is not entirely accurate. To develop a preliminary forecasting model for the carbonate hardening potential of various MWs, further studies are needed to identify additional key factors influencing the carbonate hardening process of MWs. Full article

This work investigates Ferro-Rock concrete as a carbon-negative alternative to ordinary Portland cement (OPC), which accounts for 5–9% of global CO₂ emissions, and evaluates its viability as a sustainable construction material. Ferro-Rock is an iron-based binder comprising recycled iron powder, fly ash, metakaolin, limestone powder, and oxalic acid. This is enhanced by a carbonation reaction in which iron particles react with CO₂ and water to form iron (II) carbonate (FeCO₃), the main binding phase, thereby locking in atmospheric CO₂. The experimental program was divided into two groups. Group 1 studied 100% Ferro-Rock binders with different types of aggregate, specimen sizes, and CO₂ curing periods (0–6 days) with a new locally manufactured stainless steel curing chamber that provided a controlled CO₂ environment of 99.9% and 1.2–1.5 bar gauge pressure. Group 2 investigated Ferro-Rock as a partial cement replacement at 0%, 5%, 10%, 15% and 20% levels of substitution with 5% increments. The 7 and 28 days of compressive, flexural and indirect tensile strengths were determined. The results showed the Ferro-Rock with 100% iron ductile waste aggregates (Mix F4) achieved a 28-day compressive strength of 5.5 MPa, 37.5% higher than the standard Ferro-Rock reference mix. The optimum replacement range of Group 2 was 5–10% with an increase in compressive strength by 5–10%, flexural strength by 11%, and indirect tensile strength by 16% over the OPC control. When replacement exceeded 25%, the bonding was weakened, and all strength measures decreased significantly, reaching a 46% reduction in compressive strength at 50% substitution. Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) microstructural analysis verified the gradual formation of the iron carbonate crystalline phase and provided mechanistic insights into the observed strength trends. Fully cured Ferro-Rock specimens sequestered as much as 11% CO₂ by weight, with a verifiably carbon-negative profile that no OPC-based system can match. Full article

Currently, construction uses a vast array of materials that, while serving the same purpose, differ only slightly in their properties. This complicates the substitution of one material for another, significantly expanding the product range when considering operating conditions, necessitating expanded warehouse space. Therefore, preference should be given to universal materials that, while maintaining the same chemical composition, can change their properties by altering the ratio of their components. This study addresses this issue by evaluating the potential of glass composites containing powdered waste glass as alternatives to selected conventional construction materials. The results demonstrated that the rheological properties of the composites can be effectively controlled by adjusting the ratio of water glass to waste glass powder, enabling the achievement of viscosity values suitable for both plastering and installation mortars. In addition, the composites exhibited markedly higher adhesion strength than conventional gypsum mortars under high-humidity conditions, confirming their applicability as adaptable, substrate-specific materials with geopolymer-like characteristics. Full article

Promoting construction waste utilization, this study explores using 30% mass fraction recycled micro powder (brick/concrete/hybrid) to replace cement in A03 foam concrete, as well as microbial foaming agents for insulation boards. The results show that hybrid micro powder foam concrete achieved higher compressive strength (0.7 MPa, 0.65 MPa) than pure brick (0.54 MPa) and concrete powder (0.61 MPa). For 30% hybrid micro powder insulation boards (brick:concrete ratios 2:8–8:2), when the ratio is 4:6, their performance meets JC/T 2200-2013 standards. At this point, the compressive strength is 0.43 MPa, the drying shrinkage is 0.29 mm, and the thermal conductivity 0.062 is W/(m·K). As the proportion of recycled brick powder increases, the material properties first improve and then decline, indicating that the proportion of recycled brick powder has a significant impact on the material’s overall performance; within an appropriate range, optimal performance can be achieved. Full article

The increasing demand for sustainable construction materials has intensified interest in reusing ceramic waste as a supplementary material in cementitious systems due to its potential to reduce environmental impacts and enhance resource efficiency. Previous studies indicated that ceramic roof tile waste powder (CTP) with a fineness value greater than that of cement did not contribute to an enhancement in the compressive strength of mortar. This study investigates CTP with a higher fineness than cement. Experimental parameters include fineness analysis, mortar flow, setting time, and compressive strength test. The instruments used are the Blaine tools for fineness testing, the flow table for mortar flow testing, the Vicat tools for setting time testing, and the Mortar Compression Machine for compressive strength testing. Mortar specimens (5 × 5 × 5 cm³) were prepared by partially replacing cement with CTP at different substitution levels. The results indicate that the addition of finely ground CTP increases mortar flow, extends setting time, and enhances compressive strength, suggesting its potential as a supplementary cementitious material in mortar applications. Full article

This study systematically investigated the alkali activation behavior of construction waste micro-powder (CWM) to develop a low-carbon, high-performance cementitious material. The activator formulation was optimized, the hydration thermodynamics were analyzed, and a kinetics model was constructed to reveal the reaction mechanism. The composite activator (sodium silicate and Portland cement) exhibited a significant synergistic effect, outperforming single activators. The optimal ratio was determined: 40% CWM, 60% Portland cement, and 8% water glass (modulus 1.0), which balances the system’s alkalinity and silicate modulus. Thermogravimetric analysis revealed a notable net weight gain at 3 days, indicating an ongoing secondary hydration reaction. By 7 days, the main hydration was complete, accompanied by microstructural densification, which confirmed the efficiency of the composite activator. A key contribution was the successful application of the Krstulović–Dabić (KD) model to quantify the hydration mechanism. The hydration process evolved sequentially through nucleation and growth (NG, dominant before 0.05~0.15 h), phase boundary reaction (I), and diffusion (D). The period of 0.21–50 h was governed by both I and D, after which D became the sole rate-limiting step. The model yielded the rate constants (K_NG, K_I, K_D), Avrami exponent (n), and transition points (α1, α2), providing a kinetic explanation for the ‘early strength and rapid hardening’ characteristic. In conclusion, this work establishes a material design framework guided by activator optimization, supported by thermodynamics, and explained by kinetics. The KD model proves to be a powerful tool for deciphering the hydration behavior of alkali-activated CWM, offering theoretical guidance for developing sustainable cementitious materials with controllable performance. Full article

This study presents a novel, rapidly synthesized geopolymer foam fabricated from granite industrial waste using microwave sintering, reducing the demolding time from 7 days to 3 min and the overall processing time to 24 h, while enhancing mechanical performance. Five sample compositions (G1–G5) were prepared with varying granite powder and alkaline solution ratios, cured in a microwave for 3 min, and sintered for an additional 3 min. X-ray fluorescence (XRF), compressive strength tests, water absorption, thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier transform infrared spectroscopy (FTIR) were used for thorough characterization. The compressive strength increased progressively from 13 MPa (G1) to 20 MPa (G5), the total porosity decreased from 33.33% to 18.58%, the water absorption reached a minimum of 2.02% (G5), and the bulk density rose from 1.143 to 1.49 g/cm³. XRF analysis confirmed Si/Al molar ratios of 6.5–11.4, indicating enhanced aluminosilicate network development. FTIR confirmed progressive geopolymerization, with integrated Si-O-T band areas increasing from 41,900 a.u. (G1) to 44,680 a.u. (G5). The microwave sintering approach consumed over 90% less active energy than conventional thermal curing, significantly reducing associated CO₂ emissions and thereby supporting SDG 7, SDG 12, and SDG 13. These results position granite-waste-derived geopolymer foam as a high-performance, energy-efficient alternative to conventional fired bricks and cement-based construction materials. Full article

The rapid development of tropical island tourism has put forward a higher demand for asphalt pavement construction on the island. However, the asphalt pavement engineering in the offshore area is generally faced with high material transportation costs. Additionally, challenges such as high-temperature climate and heavy-load traffic may lead to permanent pavement deformation. As a typical marine solid waste, shells have high calcium carbonate content and porous structures, which have the potential advantage of modified asphalt. In this study, mixed shell powder was used as a modified material, and 70 # base asphalt and SBS-modified asphalt were mixed, respectively. The effect of asphalt modification was analyzed by basic performance tests and high-temperature rheological tests. An asphalt mixture was prepared by replacing limestone powder with mixed shell powder in equal volume, and its road performance was systematically tested. The modification mechanism was revealed by means of a microscopic test. The results show that the recommended content of mixed shell powder in SBS-modified asphalt is 9%, and 50–100% mixed shell powder can be used to replace mineral filler in base asphalt and single SBS modified asphalt mixture. This study provides effective technical support for the utilization of shell solid waste in offshore areas and the optimization of asphalt pavement performance. Full article

One definition of environmental sustainability is one that permits the maintenance of long-term environmental quality while preventing the depletion or degradation of natural resources. In the realm of concrete production, engineers are becoming more interested in sustainable development, which includes using locally available resources and repurposing industrial and agricultural waste in building construction as a potential remedy for economic and environmental problems. The purpose of the study is to determine how various ratios of waste steel and polypropylene fibers affect the compressive strength, tensile strength, flexural strength and density of reactive powder concrete composite at different ages. According to the test results, Mix 6, which contains 100% waste steel fiber and 0% polypropylene fiber, improves the mechanical properties of reactive powder concrete by 29% in compressive strength, 47% in tensile strength, 29% in flexural strength, and 6.1% in density when compared to the reference mix. Reactive powder concrete’s waste steel fiber content has been shown to effectively reduce cracking and increase splitting tensile strength. Statistical analysis using ANOVA and Tukey HSD confirmed that fiber type has a significant effect on the compressive strength of RPC, with mixes containing higher proportions of waste steel fibers demonstrating superior performance. Full article

Using solid waste as supplementary cementitious materials (SCMs) is an effective strategy for promoting low-carbon construction development. However, single or binary systems often exhibit mismatched reaction kinetics, thereby limiting their performance at high cement replacement rates. This study focuses on a novel low-carbon concrete designed based on reaction sequence coordination, containing recycled brick powder (RBP), ground granulated blast-furnace slag (GGBS), and self-combusting coal gangue (SCCG). The effects of RBP, GGBS, and SCCG on the hydration process and microstructure of the novel low-carbon concrete with different replacement levels have been studied by testing compressive strength, workability, and durability and observing microstructural changes. The results showed that an optimized ternary composition with an RBP:GGBS:SCCG ratio of 4:3:1 achieves a cement replacement level of 30% while exhibiting a 28-day compressive strength of 38.26 MPa, representing a 14.2% increase compared with plain cement mortar. Microstructural analyses indicate that this enhanced performance results from a time-dependent reaction sequence, in which GGBS contributes predominantly at early ages by supplying calcium, whereas RBP and SCCG mainly participate through delayed pozzolanic reactions and pore refinement at later ages. Consequently, the optimized ternary mortar exhibits a water absorption of 11.12% and a 27.2% reduction in electrical flux. This study aims to provide practical strategies for enhancing the performance of low-carbon cementitious materials through a reaction sequence coordination design approach, thereby improving the utilization efficiency of solid waste in the production of low-carbon building materials. Full article

Flat glass waste from building demolition is an underused resource with potential to reduce the climate impact of construction materials. This study compares two recycling pathways for flat glass waste: the first is closed-loop recycling into new glass, and the second is the use of glass in concrete as a replacement for cement. The comparison is based on life cycle, circularity assessment and experimental evaluation of concrete performance. Recycling flat glass into new glass can reduce emissions by 945 kg CO₂eq per ton of recycled glass when the production mix contains 65 percent recycled content. However, only between 1 and 3% percent of demolition flat glass is suitable for this process because of contamination and quality limitations. As a result, the practical climate benefit of demolition glass in new glass production is limited to about 38 kg CO₂eq per ton of demolition glass. Concrete offers a much larger waste sink. Replacing 20% of cement with milled glass powder results in emission savings of 776 kg CO₂eq per ton of glass. A concrete mix containing 33% glass shows the same compressive strength as a reference mix. Full article

Artificial composite stones have recently attracted attention as multifunctional materials for construction and defense-related applications. In this study, a novel composite stone was developed using waste limestone as the primary mineral filler, combined with an unsaturated polyester resin matrix and reinforced with glass powder and chopped glass fibers. The influence of binder content and reinforcement type on physico-mechanical and microstructural behavior was investigated. Experimental characterization included water absorption, compressive strength, abrasion resistance, acid resistance, and optical microscopy. The results demonstrated that fine fillers improved matrix densification and reduced porosity, while short glass fiber reinforcement enhanced load-bearing capacity. Abrasion resistance and durability were found to depend on binder content and particle packing characteristics. Overall, the developed composite material exhibits promising mechanical performance, low water absorption, and improved durability, suggesting its potential as a candidate material for applications requiring environmental resistance, including potential use in defense-related camouflage applications. Full article

The recycling of waste clay bricks as raw materials for cement-based materials presents an effective solution to ecological pollution and resource shortages. Previous research has separately examined the effects of recycled brick fine aggregate and recycled brick powder on mortar or concrete, but few studies have investigated their combined use. This study aims to clarify the synergistic effect of recycled brick fine aggregate (RBA) and recycled brick powder (RBP) on mortar performance, quantify the influence of the RBP substitution rate on hydration characteristics and microstructural evolution, and determine the optimal mix proportion and curing system for fully recycled brick mortar. Mortar was prepared using 100% RBA and RBP at substitution rates of 0%, 10%, 20%, and 30%. The physical properties, mechanical performance, and durability of the mortar were evaluated, alongside an analysis of its microstructural morphology, mineral composition, and pore structure. The results indicate that adding an appropriate amount of RBP helped maintain the flowability of the mortar. As the RBP substitution rate increased, the mortar strength generally decreased in the early stages, but long-term curing (≥90 days) effectively mitigated this decline. The inclusion of RBP improved chloride ion permeability, with the 20% substitution rate achieving a favorable balance between compressive strength, fluidity, and durability without significantly affecting carbonation resistance. Microstructural analysis revealed that RBP regulated the morphology of hydration products and optimized the pore structure of the mortar, while the mineral composition of hydration products was similar to that of natural mortar. These findings provide a theoretical basis and technical support for the high-value utilization of construction and demolition waste in cement-based materials. Full article