Activation mechanism and performance of full solid-waste cementitious materials using modified concrete waste slurry as an activator

Comprehensive utilization of blast furnace slag, municipal sludge and kaolin clay in building brick manufacture: Crystalline transformation, morphology observation and property assessment

<p class="Paragraph" style="margin-bottom:2.0pt;"><span lang="EN-US">This experimental study explores the use of Ground Granulated Blast Furnace Slag (GGBS) and dolomite as alkali activated binders and copper slag as aggregate to achieve a cost-effective and sustainable Ultra-High-Performance Geopolymer Concrete (UHPGC). Several concrete compositions utilizing copper slag as a substitute for natural aggregates were formulated. Tests have shown that the inclusion of 100% copper slag fine aggregate leads to significant improvements in the mechanical properties and density of geopolymer concrete. Specifically, the compressive strength increased by 56.8% and the density increased by 17.5%. To understand the influence of dolomite in GGBS binder, several mixes varying dolomite proportion in GGBS were examined. The compressive strength of the 80% GGBS/20% dolomite geopolymer matrix is 32.8% higher compared to the compressive strength of UHPGC with 100% GGBS. The UHPGC mixture containing 1% crimped steel fibers showed the highest compressive strength, measuring 146.6 MPa. The split tensile and flexural strengths of the 20% dolomite matrix show a significant increase of 30.55% and 30.24% respectively compared to the 100% GGBS matrix. The water absorption and porosity of the 100% GGBS specimen were found to be lower compared to the 20% dolomite UHPGC specimen. The microscopic study reveals the positive impact of dolomite and GGBS on enhancing the bonding of the geopolymer matrix along with decreasing permeability. This study highlights the potential of geopolymer technology in producing ultra-high-performance concrete using GGBS, dolomite, and copper slag.</span></p>

The efficient resource utilization of industrial solid wastes, such as ground granulated blast-furnace slag (GGBS) and coal gangue (CG), is essential for sustainable development. However, their activation commonly depends on expensive and corrosive chemical alkalis. This study proposes a solution by developing a fully waste-based cementitious material using calcium carbide slag (CS), another industrial residue, as an eco-friendly alkaline activator for the GGBS-CG system. The influence of CS dosage (0–20 wt%) on hydration evolution and mechanical properties was examined using uniaxial compression testing, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicated that a CS dosage of 10 wt% yielded the highest compressive strength, reaching 10.13 MPa—a 16.5% improvement compared to the 20 wt% group. This enhancement is ascribed to the formation of hydrotalcite (HT) and calcium silicate hydrate (C-(A)-S-H) gel, which densify the microstructure. In contrast, higher CS contents led to a passivation effect that restrained further reaction. This work offers a practical and theoretical basis for the development of low-carbon, multi-waste cementitious materials and presents a promising strategy for large-scale valorization of industrial solid wastes.

Developing green, low-carbon building materials has become a viable option for managing bulk industrial solid waste. This paper presents a kind of all solid waste cementitious material (SWCM), which is made entirely from six common industrial wastes, including carbide slag and silica fume, that demonstrate strong mechanical properties and effectively stabilize aeolian sand (AS). Initially, we investigated the mechanical strength of waste-based cementitious materials in various mix ratios, focusing on their ability to stabilize river sand (RS) and aeolian sand. The results show that it is necessary to use alkaline solid waste carbide slag to provide a suitable reaction environment to achieve the desired strength. In contrast, the low reactivity of coal gangue powder did not contribute effectively to the strength of the cementitious material. Further orthogonal experiments determined the impact of different waste dosages on the strength of stabilized AS. It was found that increasing the amounts of carbide slag, silica fume, and blast furnace slag powder improved strength, while increasing fly ash first increased and then decreased strength. In contrast, higher additions of desulfurization gypsum and coal gangue powder led to a continuous decrease in strength. The optimized mix is carbide slag—desulfurization gypsum—fly ash—silica fume—blast furnace slag powder in a ratio of 4:2:2:3:3. The experimental results using SWCM to stabilize AS indicated a proportional relationship between strength and SWCM content. When the content is ≥20%, it meets the strength requirements for road subbases. The primary hydration products of stabilized AS are C-(A)-S-H, AFt, and CaCO3. Increasing the SWCM content enhances the reaction degree of the materials, thereby improving mechanical strength. This study highlights the mechanical properties of cementitious materials made entirely from waste for stabilizing AS. It provides a reference for the large-scale utilization of industrial solid waste and practical applications in desert road construction.

Hydration characteristics and sustainability of calcium carbide slag-activated full solid waste cementitious materials under high temperature curing.

To promote the resource utilization of industrial solid waste, this study developed a multi-source industrial solid waste cementitious material (MSWC) for fluidized solidified soil (FSS), which consists of steel slag (SS), granulated blast furnace slag (GBFS), circulating fluidized bed fly ash (CFBFA), desulfurization gypsum (DG) and ordinary Portland cement (OPC). Firstly, the influence of industrial solid waste contents on the unconfined compressive strength (UCS) of FSS solidified with MSWC (MSWC-FSS) was studied, and the optimal proportion for MSWC was determined as SS:GBFS:CFBFA:DG:OPC = 20:40:15:5:20. Then, the effects of water reducers (PCE and FDN) and early-strength agents (Na2SO4 and CaCl2) on the flow expansion, setting time and UCS of MSWC-FSS were studied. With the increase of PCE and FDN, the flow expansion, setting time and UCS of MSWC-FSS increased. With the increase of Na2SO4 and CaCl2, the flow expansion and setting time of MSWC-FSS decreased, and 3 d and 7 d UCS increased, and 28 d UCS first increased and then decreased. The best mixing scheme of water reducer and admixture is 0.5% PCE and 1% Na2SO4, respectively. Finally, the sustainability of MSWC-FSS was assessed. The heavy metal leaching of MSWC-FSS met the safety requirements. For FSS cementitious materials, the cost and carbon emissions of MSWC were only 43.9% and 22.4% of OPC, respectively.

To enhance the efficient utilization of industrial solid waste and support the low-carbon transition of cementitious materials, this study used steel slag, coal-fired slag, and desulfurization gypsum as the primary raw materials. A high-performance composite cementitious material system was developed based on the synergistic effects of physical activation (mechanical grinding) and chemical activation (alkali stimulation). This study systematically investigates the raw material characteristics, mix proportion optimization, mechanical behavior, and durability of composite cementitious materials through the integration of response surface optimization design and multi-scale analysis methods. The results indicate that the optimal mix proportions of the composite cementitious material are: 37.2% steel slag, 33.2% coal-fired slag, 9.6% desulfurized gypsum, 20% cement, 4% sodium silicate, and 0.1% superplasticizer. At this mix proportion, the measured 28-day average compressive strength of the composite cementitious material was 40.8 MPa, which closely matched the predicted value of 41.2 MPa from the response surface regression model, thereby confirming the model’s accuracy and applicability. The composite cementitious material demonstrated superior volume stability compared to ordinary cement under both water-curing and drying conditions. However, its freeze–thaw resistance and carbonation resistance were lower than those of cement. Therefore, considering these factors comprehensively, the composite cementitious material is recommended for application in road base and subbase layers.

Effects of gypsum type, content and slag on the performance of sleeve grouting materials

Comprehensive evaluation of low-carbon cementitious materials prepared with industrial by-product calcium carbide residue (CCR) as alkali source.

Feasibility of preparing red mud-based cementitious materials: Synergistic utilization of industrial solid waste, waste heat, and tail gas

This research project accomplished a study on the technical feasibility of recycling industrial solid waste generated by the discharge of casting sand agglomeration with clay and blast furnace slag. For this, the plan proposed a methodology that initially establishes a process of solid waste encapsulation, by using solidification/stabilization technique on Portland cement matrices, in which the residuals act as small and large aggregates on the composition of concrete, and later it presents the possibility of using this concrete in the manufacture of concrete pieces (concrete blocks) for paving. The results obtained in this research achieved the objective set with great success, regarding the manufacturing of concrete pieces (blocks) for paving urban roads, whenever there is special vehicle traffic or demands capable of producing accentuated abrasion effects (surpassing the 50 MPa required by the regulation), which probes the technical practicability of using waste from sand casting agglomeration with clay and blast furnace slag used in this study, unlocking usage possibilities for construction.

Insufficient utilization of industrial solid waste and the high carbon emissions caused by the use of cement in engineering construction are two challenges faced by China. This study aimed to develop a multi-source industrial solid waste cementitious material (MSWC) for fluidized solidified soil (FSS) in soil backfill projects. First, the response surface models for the unconfined compressive strength (UCS) of MSWC-FSS were established, and the optimal mixing ratio of MSWC was determined. Subsequently, laboratory tests were conducted to compare the differences in flow expansion, UCS, and dry shrinkage between MSWC and ordinary Portland cement (OPC) in FSS, and the feasibility of MSWC-FSS was verified through on-site tests. Finally, the curing mechanism of MSWC-FSS was analyzed by XRD and SEM. The results showed that MSWC had an optimal mix ratio: steel slag (SS): ground granulated blast-furnace slag (GGBS): circulating fluidized bed fly ash (CFBFA): flue gas desulfurization gypsum (FGDG): OPC = 20:40:15:5:20. MSWC-FSS had good flow expansion, and its UCS and drying shrinkage resistance were more than 10% better than OPC-FSS. The on-site test also proved the practicability and progressiveness of MSWC-FSS. According to the chemical composition and microstructure, MSWC-FSS generated more ettringite than OPC-FSS, making MSWC-FSS denser.

Utilization of industrial solid waste as a mold material in the foundry industry

Industrial solid waste is characterized by complex mineral phases and various components. Low-carbon cementitious materials can be prepared through precise regulation based on the material composition and properties of various industrial solid wastes. In this study, electrolytic manganese residue (EMR), carbide slag (CS), and granulated blast-furnace slag (GBFS) were used as alternatives to cement to prepare multicomponent solid waste cementitious materials. The effects of the proportions of EMR and CS on the cementitious activity of GBFS and the activation mechanism of alkali and sulfur were studied. The results showed that with increasing EMR content, the strength first increased and then decreased. At a GBFS content of 20%, CS content of 2%, and EMR content of 8%, the compressive strength was highest, reaching 45.5 MPa after 28 days of curing, mainly because the OH− in CS and SO42− in EMR synergistically stimulated the active components in GBFS. Hydrated products such as ettringite and hydrated calcium silicate (C–S–H gel) were generated and interlaced with each other to improve the densification of the mortar. Overall, the proposed system provides an avenue to reduce or replace the production of cement clinker and achieve the high-value-added utilization of industrial solid waste.

Steel slag and GBFS are wastes generated during the steel and iron smelting process, characterized by their considerable production rates and extensive storage capacities. After grinding, they are often used as supplementary cementitious materials. However, the intrinsic slow hydration kinetics of steel slag–GBFS cementitious material (SGM) when exposed to a pure water environment result in prolonged setting times and diminished early-age strength development. The incorporation of modifiers such as gypsum, clinker, or alkaline activators can effectively improve the various properties of SGM. This comprehensive review delves into existing research on the utilization of SGM, examining their hydration mechanisms, workability, setting time, mechanical strengths, durability, and shrinkage. Critical parameters including the performance of base materials (water-to-cement ratio, fineness, and composition) and modifiers (type, alkali content, and dosage) are scrutinized to understand their effects on the final properties of the cementitious materials. The improvement mechanisms of various modifiers on properties are discussed. This promotes resource utilization of industrial solid wastes and provides theoretical support for the engineering application of SGM.