Search Results (31)

This study explores the potential of calcium carbide residue (CCR) as an alternative activator for ground granulated blast-furnace slag (GGBS) to reduce reliance on ordinary Portland cement (OPC) in mortar production. A series of OPC-GGBS-CCR ternary binders were prepared and evaluated for their fresh and mechanical properties over various curing periods. The findings showed that mortars’ fresh and mechanical characteristics were significantly improved with longer curing times, suggesting CCR’s potential to efficiently activate GGBS, thereby benefiting the environment and economy. Significant enhancements in compressive strengths were observed after 7 days of curing, with increases of 44%, and 69–144% for OPC and OPC-GGBS-CCR ternary binders, respectively, while the utilization of activated binders led to flexural strength growth compared to three days of curing, with improvements of 70–173% for OPC-GGBS-CCR ternary binders, respectively. Microstructural analyses confirmed accelerated hydration and increased product formation due to CCR’s calcium content. An optimal mix ratio of OPC:GGBS:CCR = 1:1:0.5 demonstrated mechanical properties comparable to OPC mortars after 28 days, highlighting CCR’s potential for sustainable cementitious materials. Full article

This study aims to enhance the sustainable utilization of electrolytic manganese residue (EMR), an industrial solid waste rich in sulfates and pollutants, by modifying it with appropriate proportions of granulated blast furnace slag (GBFS) and carbide slag (CS) and evaluating its potential as a cement retarder. The influence of both the GBFS/CS ratio and the dosage of modified EMR on the performance of cement mortar was systematically investigated, focusing on workability, mechanical properties, hydration behavior, leaching toxicity, and carbon emissions. Results showed that GBFS and CS significantly reduced pollutant concentrations in EMR while improving gypsum crystallinity. Modified EMR exhibited retarding properties, extending the initial and final setting times of cement mortar from 98 min and 226 min to 169 min and 298 min. With an 8 wt.% dosage, the 28-day compressive strength reached 58.76 MPa, a 1.3-fold increase compared to cement mortar (45.21 MPa). The content of reactive SiO₂, Al₂O₃, Ca(OH)₂, and CaSO₄·2H₂O promoted secondary hydration of cement and generated significant ettringite (AFt) and calcium silicate hydrate (C-S-H) gels, forming a dense microstructure. Pollutants in the modified EMR-cement mortar were reduced through precipitation, substitution, and encapsulation, meeting leaching toxicity standards. This study highlights the feasibility and environmental benefits of employing modified EMR as a cement retarder, demonstrating its potential in sustainable building materials. Full article

This study utilizes machine learning (ML) techniques to predict the performance of slag-based cemented tailings backfill (CTB) activated by soda residue (SR) and calcium carbide slag (CS). An experimental database consisting of 240 test results is utilized to thoroughly evaluate the accuracy of seven ML techniques in predicting the properties of filling materials. These techniques include support vector machine (SVM), random forest (RF), backpropagation (BP), genetic algorithm optimization of BP (GABP), radial basis function (RBF) neural network, convolutional neural network (CNN), and long short-term memory (LSTM) network. The findings reveal that the RBF and SVM models demonstrate significant advantages, achieving a coefficient of determination (R²) of approximately 0.99, while the R² for other models ranges from 0.86 to 0.98. Additionally, a dynamic growth model to predict strength is developed using ML techniques. The RBF model accurately predicts the time required for filling materials to reach a specified strength. In contrast, the BP, SVM, and CNN models show delays in predicting this curing age, and the RF, GABP, and LSTM models tend to overestimate the strength of the filling material when it approaches or fails to reach 2 MPa. Finally, the RBF model is employed to perform coupling analysis on filling materials with various mix ratios and curing ages. This analysis effectively predicts the changes in filling strength over different curing ages and raw material contents, offering valuable scientific support for the design of filling materials. Full article

Red mud is a kind of solid waste in the production process of the aluminum industry. The long-term stockpiling of red mud not only occupies a large amount of land but also causes environmental pollution. In order to improve the strength, reduce the alkalinity and toxicity of red mud, and study its durability under freeze–thaw cycles, CGFPA binders, whose components were calcium carbide residue, ground granulated blast furnace slag, fly ash, phosphogypsum, and graphene, were adopted to solidify/stabilize red mud in this paper. The effects and the mechanism of freeze–thaw cycling on the unconfined compressive strength, pH value, and toxic leaching of the solidified/stabilized red mud was investigated. The micro-mechanism was analyzed by XRD, SEM-EDS, and FT-IR. The results of the study showed that the mass, unconfined compressive strength, and pH of the solidified/stabilized red mud decreased gradually with an increase in the number of freeze–thaw cycles, while the leaching concentration of pollutants increased gradually. The rate of loss of unconfined compressive strength satisfies an exponential function with the number of cycles, and the logarithm of pollutant concentration satisfies a linear relationship with the number of cycles. The cumulative loss of mass was 6.7%, 5.4%, 3.6%, and 3.3%, and the cumulative loss of unconfined compressive strength was 50.6%, 47.5%, 32.2%, and 25.3%, and the pH value was reduced to 9.42, 9.54, 9.80, and 9.92, respectively, after 10 freeze–thaw cycles at binder mixing ratios of 15%, 20%, 25%, and 30%, while the leaching concentrations of Cu, Zn, Cr, Ni, As, Pb, and Cd increased from 7.4 μg/L, 87.2 μg/L, 5.2 μg/L, 7.0 μg/L, 6.9 μg/L, 3.7 μg/L, and 0.7 μg/L to 17.5 μg/L, 123.5 μg/L, 10.2 μg/L, 15.7 μg/L, 11.4 μg/L, 5.6 μg/L, and 4.9 μg/L, respectively, under the condition of a 30% incorporation ratio. The gelling products generated by the hydration reaction of the binders were mainly C-S-H, C-A-S-H, C-A-H, AFm, etc. Under the action of freeze–thaw cycles, the lattice-like structure of the solidified/stabilized red mud was damaged, resulting in a decrease in its unconfined compressive strength and an increase in pollutant leaching concentration. The research results can provide a theoretical basis for the use of red mud in permafrost regions. Full article

This study developed a sustainable low-carbon cementitious material using calcium carbide residue (CCR) as an alkali activator, combined with ground granulated blast furnace slag (GGBS) and fly ash (FA) to form a composite. The objective was to optimize the CCR dosage and the GGBS-to-FA ratio to enhance the unconfined compressive strength (UCS) of the composite, providing a viable alternative to traditional Portland cement while promoting solid waste recycling. Experiments were conducted with a water-to-binder ratio of 0.55, using six GGBS-to-FA ratios (0:10, 2:8, 4:6, 6:4, 8:2, and 10:0) and CCR contents ranging from 2% to 12%. Results indicated optimal performance at a GGBS-to-FA ratio of 8:2 and an 8% CCR dosage, achieving a peak UCS of 18.04 MPa at 28 days, with 79.88% of this strength reached within just 3 days. pH testing showed that with 8% CCR, pH gradually decreased over the curing period but increased with higher GGBS content, indicating enhanced reactivity. Microstructural analyses (XRD and SEM-EDS) confirmed the formation of hydration products like C-(A)-S-H, significantly improving density and strength. This study shows CCR’s potential as an effective and environmentally friendly activator, advancing low-carbon building materials and resource recycling in construction. Full article

Gypseous soil is a collapsing soil that has not yet been approved as a construction material since its behavior under water, temperature, and pressure is unreliable and unpredictable. Researchers and scientists are always searching for new and creative ways to optimize the benefits of calcium carbide residue (CCR) recycling, which is a byproduct of the acetylene industry and includes a substantial quantity of Ca(OH)₂. Therefore, it is a suitable choice for utilization as a chemical stabilizer to improve the engineering features of problematic soils. However, this study explores the potential for enhancing the engineering characteristics of gypseous soil by utilizing (CCR) combined with linear alkyl benzene sulfonic acid (LABSA) to form a geopolymer. The soils utilized in this work are gypseous collapsible soils. Standard tests were conducted on these soils to identify the physical and mechanical characteristics. The geopolymer preparation was accomplished by merging a dilution of LABSA with a geopolymer (solid to liquid), blending the proportions. Three different types of disturbed natural granular-gypseous collapsible soils with different properties and various gypsum contents with percentages of 20%, 35%, and 50% were used. Mixtures of soils containing (2.5%, 5%, and 7.5%) of the geopolymer mix content were made. The single oedometer test (SOT) and the double oedometer test (DOT) were carried out to ascertain the lowest collapse potential value correlated with the ideal geopolymer mixing ratio. The adequate geopolymer percentage was found to be 5% since it resulted in the maximum reduction in collapse potential compared to the natural soil. The direct shear test is employed to ascertain the soil samples’ cohesiveness and friction angle. The results show a slight reduction in the angle of internal friction and increased cohesion (c). For stabilizing gypseous soil in engineering projects, a combination of LABSA and CCR can be utilized as a workable, sustainable, and environmentally friendly substitute. Full article

Stone waste refers to the waste stone particles generated from mining and stone processing to finished products that are not utilized in a resourceful manner. In this study, a CGF solid waste-based binder (abbreviated as CGF), with calcium carbide residue (CCR), ground granulated blast-furnace slag (GGBS), and fly ash (FA) as components, was developed to solidify the stone waste. Through “treating waste with waste”, the resource utilization of solid waste was realized. In order to improve the performance of the new material, this paper proposes the MAA-SW model for stone waste pavement base material based on the MAA model, establishes the relationship with the target gradation, and obtains the ideal gradation composition of stone waste through the calculation of the response surface analysis so as to obtain an energy-saving stone waste pavement base material with excellent performance. Full article

The disposal of stone waste derived from the stone industry is a worldwide problem. The shortage of landfills, as well as transport costs and environmental pollution, pose a crucial problem. Additionally, as a substitute for cement that has high carbon emissions, energy consumption, and pollution, the disposal of stone wastes by utilizing solid waste-based binders as road base materials can achieve the goal of “waste for waste”. However, the mechanical properties and deterioration mechanism of solid waste-based binder solidified stone waste as a road base material under complex environments remains incompletely understood. This paper reveals the durability performance of CGF all-solid waste binder (consisting of calcium carbide residue, ground granulated blast furnace slag, and fly ash) solidified stone waste through the macro and micro properties under dry–wet and freeze–thaw cycling conditions. The results showed that the dry–wet and freeze–thaw cycles have similar patterns of impacts on the CGF and cement stone waste road base materials, i.e., the stress–strain curves and damage forms were similar in exhibiting the strain-softening type, and the unconfined compressive strengths all decreased with the number of cycles and then tended to stabilize. However, the influence of dry–wet and freeze–thaw cycles on the deterioration degree was significantly different; CGF showed excellent resistance to dry–wet cycles, whereas cement was superior in freeze–thaw resistance. The deterioration grade of CGF and cement ranged from 36.15 to 47.72% and 39.38 to 47.64%, respectively, after 12 dry–wet cycles, whereas it ranged from 57.91 to 64.48% and 36.61 to 40.00% after 12 freeze–thaw cycles, respectively. The combined use of MIP and SEM confirmed that the deterioration was due to the increase in the porosity and cracks induced by dry–wet and freeze–thaw cycles, which in turn enhanced the deterioration phenomenon. This can be ascribed to the fact that small pores occupy the largest proportion and contribute to the deterioration process, and the deterioration caused by dry–wet cycles is associated with the formation of large pores through the connection of small pores, while the freeze–thaw damage is due to the increase in medium pores that are more susceptible to water intrusion. The findings provide theoretical instruction and technical support for utilizing solid waste-based binders for solidified stone waste in road base engineering. Full article

The alkali-activated blast furnace slag is attracting significant attention in replacing Portland cement due to several characteristics similar to cement hydration. However, there are a few practical problems with commercial alkali activators, such as the fast setting time, relatively high costs, and significant CO₂ emissions during preparation. Thus, discovering industrial residues possessing inherent alkalinity are urgent. This study proposes the use of carbide slag at levels of 0%, 5%, 10%, 15%, 20%, and 30% and alkali at levels of 1%, 2%, 3%, 4%, 5%, 6%, 8%, and 10% activated blast furnace slag. The compressive strength and microstructure of carbide slag and alkali-activated blast furnace slag (CAB) pastes were examined using X-ray diffraction analysis (XRD), Differential Scanning Calorimetry/Thermogravimetric Analysis (DSC/TG), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results revealed that the addition of carbide slag produced more hydrotalcite-like phase as well as decreased the content of ettringite (AFt) and the calcium–silicate–hydrate (C-S-H) gel, which decreased the compressive strength of the CAB pastes. At the age of 28 days, when the dosage was 5%, 10%, 15%, 20%, and 30%, the compressive strength of CAB mixes decreased by 2.1%, 7.1%, 9.2%, 9.8%, and 28.1%, respectively. The addition of NaOH promoted the formation of AFt, and there was an optimum level of NaOH corresponding to the high compressive strength of paste. At the age of 3 days and 7 days, the compressive strength reached its maximum at the dosage of 6% NaOH, which was 24.8 MPa and 36.3 MPa, respectively. However, at the ages of 14 days and 28 days, the compressive strength increased as the dosage of NaOH increased to 5%, which was 43.3 MPa and 44.5 MPa, respectively. The water curing could both enhance the early and later strength, the compressive strength of 23.3 MPa was gained at 3 days, and this increased by 16.3%, 24.0% and 36.9% at 7 days, 14 days and 28 days, respectively. Therefore, water curing was suitable for the strength development of CAB pastes. Full article

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. Full article

Alkali-activated cementitious materials, as an environmentally friendly cementitious material, can effectively reduce carbon emissions and improve the utilisation of solid wastes. However, traditional strong alkali activators have limitations such as high carbon emissions and poor safety. In order to overcome the defects of traditional strong alkaline activators and realise the high value-added use of calcium carbide residue (CCR), this paper adopts CCR as an alkaline activator to activate granulated blast furnace slag (GBFS)-steel slag (SS) cementitious systems for the preparation of alkaline-activated cementitious materials. The effects of CCR content and SS content on the compressive strength and working performance of CCR-GBFS-SS cementitious systems are analysed, along with the hydration process of CCR-GBFS-SS cementitious systems and the mechanism of action through the hydration products, their chemical structure and their microscopic morphology. The research results show that CCR-GBFS-SS cementitious systems have a 28-day compressive strength of 41.5 MPa and they can be controlled by the setting time; however, the flow performance is poor. The SS content can be increased to improve the flow performance; however, this will reduce the compressive strength. In CCR-GBFS-SS cementitious systems, CCR is the main driving force of hydration reactions, GBFS mainly provides active silica and aluminium and the amorphous C-(A)-S-H gel and ettringite formed by the synergistic action of multiple solid wastes are the main sources of compressive strength. With the extension of the curing time, the amount of hydration products in the cementitious systems gradually increases and the matrix of the cementitious systems gradually becomes denser. This study will provide a reference for the consumption of low-value solid waste such as CCR and the preparation of low-carbon cementitious materials from multi-component solid wastes. Full article

Large quantities of abandoned marine soft soil are generated from coastal engineering which cannot be directly utilized for construction without modification. The utilization of traditional binders to modify abandoned marine soft soil yields materials with favorable mechanical properties and cost efficiency. However, the production of traditional binders like cement leads to environmental pollution. This study uses a CGF all-solid-waste binder (abbreviated as CGF) composed of industrial solid waste materials such as calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS), and fly ash (FA), developed by our research team, for the modification of abandoned marine soft soil (referred to as modified soil). It is noteworthy that the marine soft soil utilized in this study was obtained from the coastal area of Jiaozhou Bay, Qingdao, China. Physical property tests, compaction tests, and unconfined compressive strength (UCS) tests were conducted on the modified soil. The investigation analyzed the effects of binder content, compaction delay time, and curing time on the physical, compaction, and mechanical properties of CGF-modified soil and cement-modified soil. Additionally, microscopic experimental results were integrated to elucidate the mechanical improvement mechanisms of CGF on abandoned marine soft soil. The results show that after modification with binders, the water content of abandoned marine soft soil significantly decreases due to both physical mixing and chemical reactions. With an increase in compaction delay time, the impact of chemical reactions on reducing water content gradually surpasses that of physical mixing, and the plasticity of the modified soil notably modifies. The addition of binders results in an increase in the optimum moisture content and a decrease in the maximum dry density of CGF-modified soil, while the optimum moisture content decreases and the maximum dry density increases for cement-modified soil. Moreover, with an increase in binder content, the compaction curve of CGF-modified soil gradually shifts downward and to the right, while for cement-modified soil, it shifts upward and to the left. Additionally, the maximum dry density of both CGF-modified and cement-modified soils shows a declining trend with the increase in compaction delay time, while the optimum moisture content of CGF-modified soil increases and that of cement-modified soil exhibits a slight decrease. The strength of compacted modified soil is determined by the initial moisture ratio, binder content, compaction delay time, and curing time. The process of CGF modification of marine soft soil in Jiaozhou Bay can be delineated into stages of modified soil formation, formation of compacted modified soil, and curing of compacted modified soil. The modification mechanisms primarily involve the alkali excitation reaction of CGF itself, pozzolanic reaction, ion-exchange reaction, and carbonization reaction. Through quantitative calculations, the carbon footprint and unit strength cost of CGF are both significantly lower than those of cement. Full article

In order to realize the resource utilization of solid waste and improve the tensile strength and toughness of soil, CCR-GGBS-FA all-solid-waste binder (CGF) composed of general industrial solid waste calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS) and fly ash (FA) was used instead of cement and combined with polypropylene fiber to strengthen the silty soil taken from Dongying City, China. An unconfined compressive strength test (UCS test) and a uniaxial tensile test (UT test) were carried out on 10 groups of samples with five different fiber contents to uncover the effect of fiber content on tensile and compressive properties, and the reinforcement mechanism was studied using a scanning electron microscopy (SEM) test. The test results show that the unconfined compressive strength, the uniaxial tensile strength, the deformation modulus, the tensile modulus, the fracture energy and the residual strength of fiber-reinforced CGF-solidified soil are significantly improved compared with nonfiber-solidified soil. The compressive strength and the tensile strength of polypropylene-fiber-reinforced CGF-solidified soil reach the maximum value when the fiber content is 0.25%, as the unconfined compressive strength and the tensile strength are 3985.7 kPa and 905.9 kPa, respectively, which are 116.60% and 186.16% higher than those of nonfiber-solidified soil, respectively. The macro–micro tests identify that the hydration products generated by CGF improve the compactness through gelling and filling in solidified soil, and the fiber enhances the resistance to deformation by bridging and forming a three-dimensional network structure. The addition of fiber effectively improves the toughness and stiffness of solidified soil and makes the failure mode of CGF-solidified soil transition from typical brittle failure to plastic failure. The research results can provide a theoretical basis for the application of fiber-reinforced CGF-solidified soil in practical engineering. Full article

The recycling and reuse of waste materials is an important part of promoting sustainable development. Encouraged by cleaner production and a circular economy, the introduction of calcium carbide residue (CCR) for the stabilization of soil foundations has become a hot topic in the road engineering industry. Aiming at the efficient application of CCR-stabilized soils, the optimization of the material composition was focused on in this work. Fly ash and polypropylene fibers were introduced into the preparation of CCR-stabilized soils, and their effects on the mechanical properties and water stability were tested. The findings highlight that the strength of fly-ash–carbide-residue-stabilized soil was higher than that of carbide-residue-stabilized soil at the same curing age. Furthermore, the unconfined compressive strength, splitting strength, and water stability of CCR–fly-ash-composite-stabilized soil initially increased and then decreased with a rise in polypropylene fiber content. The peak values of confining compressive and splitting strength were observed when the polypropylene fiber content was 1.2‰, while the water stability coefficient A reached its peak value at 0.8‰. From the standpoint of the comprehensive performance improvement and economy of composite-stabilized soil, it is advised that the dosage of polypropylene fibers falls within the range of 0.8–1.2‰. The engineering technical indexes of polypropylene-fiber–CCR-composite-stabilized soil fulfilled the requirements of the specification and had a satisfactory effect on delaying the cracking of the specimen. It is expected that this investigation will provide support for the resource utilization of CCR and the sustainable development of road construction. Full article

Due to urbanization, it is nearly impossible to construct civil infrastructure without encountering soil materials with poor geotechnical response. In soil re-engineering, the trending practice is the use of supplementary cementitious material with the aim of reducing carbon footprints and construction costs. This has necessitated the usability of integrating the blends of palm oil fuel residue (POFR) and calcium carbide powder (CCP) in the amelioration protocols of two soil materials. The amelioration protocols were implemented by the inclusion of 0, 2, 4, 6, 8, and 10% dosages of POFR and 0, 2, 4, 6, and 8% dosages of CCP at the requisite weight of soil materials. The experimental work was performed in three phases, namely material characterization, mechanical performance, and microstructural testing. Judging from the index performance, black clayey soil (BCS) and reddish lateritic soil (RLS) are clayey materials with a plasticity index of 28.70 and 28.80%, respectively. Concerning the mechanical performance (compaction, California bearing ratio, and durability), the inclusion of the blends of POFR-CCP into the soils (BCS and RLS) activated a positive response and was later validated via means of microstructural tests. This research has shown the potential of blended waste residues in soil re-engineering studies. The study was vividly achieved through a qualitative approach known as scanning electron microscopy and Fourier transform infrared. Full article