Cement Compounds Research Articles

Sustainable soil stabilization using industrial waste ash: Enhancing expansive clay properties

This study investigates the use of various industrial waste materials—silica fume (SF), cement kiln dust (CKD), calcium carbide residue (CCR), rice husk ash (RHA), and ground granulated blast furnace slag (GGBS)—as eco-friendly stabilizers for expansive clay soil (ECS). Laboratory tests were conducted to assess the impact of different proportions (3 %, 6 %, and 9 %) of these additives on the soil's physical, mechanical, and microstructural properties. Results indicated that the inclusion of industrial waste significantly improved the soil's behavior, with notable reductions in liquid limit (up to 37.66 %), plasticity index (up to 74.76 %), and swell potential. Additionally, unconfined compressive strength (UCS) and shear strength increased substantially, with UCS values rising from 114.64 kPa to 1582.91 kPa at 30 days of curing for 9 % GGBS. Microstructural analyses confirmed the formation of cementitious compounds, which enhanced soil particle bonding and durability. These findings suggest that industrial waste materials can serve as effective and sustainable alternatives to traditional soil stabilizers, offering both performance improvements and environmental benefits.

ADHESIVE ABILITY OF GYPSUM-CONTAINING PLASTER COMPOSITIONS

The traditional material for the construction of buildings in the Northern Black Sea region is a cheap local stone ‒ limestone-shell rock. Most of the buildings in the central part of the city of Odesa, which are of historical and architectural value, are constructed of this material. With proper care and maintenance, these structures can perform their functions for hundreds of years, but as a result of shell rock moisture due to negligent operation and a number of other reasons, the supporting structures are damaged, followed by the collapse of the building. In many cases, the direct cause of the destruction of load-bearing walls is the damage or absence of the outer plaster layer. Repairing walls with cement compounds exacerbates the problem. The article discusses some aspects of the possible use of gypsum-based composite materials for repairing damaged walls of limestone-shell rock buildings. The requirements for the repair composition are formulated. The expediency of using gypsum as a binder for the repair plaster mixture for exterior repairs is substantiated. An ash-gypsum-cement composition was used to increase the water resistance of the plaster. Sufficient water resistance and vapor permeability of the proposed composition were confirmed. This paper presents the results of studying the adhesive strength of the contact of the developed composition with the surface of various materials. Methods and measuring equipment developed at the ODABA were used. The adhesion strength of the proposed mixture with the surface of shell rock is close to the standard strength. The use of the adhesive additive Ceresit CC 81 increases the adhesive strength of the joint of the proposed composition with shell rock by 1.5 ‒ 2 times. The optimal amount of the adhesive additive to be introduced will be determined by the results of a multifactorial experiment to study the effect of a complex of chemical additives of different functional purposes on the properties of the proposed repair composition.

Effect of in situ CO2 mixing of cement paste on the leachability of hexavalent chromium (Cr(VI))

In situ CO2 mixing technology is a potential technology for permanently sequestering CO2 during concrete manufacturing processes. Although it has been approved as a promising carbon capture and utilisation (CCU) method, its effect on the leachability of heavy metals from cementitious compounds has not yet been studied. This study focuses on the effect of in situ CO2 mixing of cement paste on the leaching of hexavalent chromium (Cr(VI)). The tank leaching test of the CO2 mixing cement specimen resulted in a Cr(VI) cumulative leaching of 0.614 mg/m2 in 28 d, which is ten times lower than that of the control mixing specimens. The results in thermogravimetric analysis indicated that a relatively significant amount of CrO42− is immobilised as CaCrO4 during the CO2-mixing, and a higher Cr–O extension is observed in the Fourier transform infrared spectra. Furthermore, a portion of the monocarboaluminate is inferred from microstructural analyses to incorporate CrO42− ions. These results demonstrate that in situ CO2 mixing is beneficial not only in reducing CO2 emissions, but also in controlling the leaching of toxic substances.

Mechanical Behaviour of Soil Treated with Chitosan and Calcium Metasilicate Considering the Fungal Growth

Biopolymers have been widely experimented with as organic stabilizers in the last decade for improving soil properties. However, the high nutritional value of some biopolymers like chitin, carrageenan, casein, and chitosan can also promote microbial growth which can affect the improvement in the strength of biopolymer-stabilized soil. This study investigates the mechanical behaviour of clay treated with chitosan at dosages of 0.5, 1.0, 1.5, and 2.0% at various curing periods of 7 d, 28 d, 56 d, and 90 d and also observes the fungal growth, the conditions favourable to fungal growth, and the effect of an inorganic secondary additive on the mechanical behaviour of treated soil. The study shows that fungal growth is higher with the time and dosage of chitosan. The strength of chitosan-treated samples increased with both dosage and age despite the fungal growth observed on the treated soil, as did the fungal growth. On treating the soil with 2% chitosan, the percentage increase in strength was nearly 14.39%, and on the 56th day, it was phenomenally increased to 1534.39%. In an attempt to control the fungal growth, a secondary additive, calcium metasilicate (calsil), was added to various dosages of chitosan-treated soil (CTS). The secondary additive did not completely stop the fungal growth but certainly controlled fungal growth. Chitosan and calsil are hydrophilic, increasing OMC by 67% and 150% for the high CTS and calsil–chitosan-treated soil (CCTS) doses. Calsil coated the soil particles and prevented closer packing under compaction, reducing MDUW by 7.8% and 18% for CTS and CCTS at maximal dosage. The development of hydrated cementitious products made the soil brittle, causing the post-peak strength of CCTS samples to diminish significantly with age. FTIR spectroscopy showed hydrogen bonding strengthening CTS, while XRD revealed cementitious compounds in CCTS. The strength of the soil treated with chitosan and calsil showed a higher strength than soil treated with only chitosan.

Mechanical behavior of calcareous tuff and coal mine tailings mixture as an embankment material for road construction

The construction of embankments requires available and suitable material that sounds to the imposed load. The selection of materials that provide slope stability and maintain pavements is made through specific test control. This research aims to analyze the mechanical behavior of a mixture of 75% calcareous tuff and 25% coal mine tailings (CMTs) used on embankment foundations. the impact of particle size characteristics and the compaction on the mechanical behavior of the mixture are studied. The direct shear test was conducted on different material states, granular and uncompressed states, compaction at the Maximum Practical Optimum (MPO), and MPO compaction post a 30-day curing period at 40 degrees Celsius. the normal stress applied ranging from 50 to 500 KPa, with a constant shear rate displacement of 0.5 mm/min. The results show a substantial influence of compaction on both friction angle (φ) and cohesion (C) values. a remarkable increase in cohesion values after the curing period, attributed to the cementitious compound formation from the interaction between calcareous tuff and coal mine tailings. This investigation emphasizes coal mine tailings potential as a sustainable and cost-effective embankment material for road construction, especially in arid regions. The material exhibits significant shear strength, with a marked increase in cohesion values post-curing state. These results are conducted to consider coal mine tailings as an appealing alternative to traditional materials of road engineering.

Examining Low-Energy Gamma-Ray Protection of a New Promising Saudi Cement Product as Alternative Cementitious Material Using Geant4 Software

In modern life, cement products have become an essential material for the foundations in many structural building designs. Because of this, the natural effects of this material need to be tested and cannot be ignored. Modeling interactions of gamma rays with several cementitious compounds is the focus of this study. Gamma radiations exist naturally and artificially, but with limited gamma-ray energies, which are not easy to access for experimental gamma attenuation studies. So in the current work, a wide range of low gamma-ray energies (0.01 to 0.356 MeV) are applied to investigate the gamma radiation attenuation properties theoretically for different cement materials. Also, the Monte Carlo statistical method is applied using the Geant4 toolkit to simulate the results. The outcomes are compared with theoretical values using XCOM to validate at these energies. The effective atomic number ( Z eff ), electron density ( N eff ), and half-value layers (HVLs) for the studied samples are computed based on the simulated mass attenuation coefficient ( μ m ), as expected. The outcomes show good agreement between the simulated results with those calculated theoretically by XCOM within an 11% deviation. The silica fume sample showed a slightly higher μ m value compared with the other samples. The dependence of the photon energy and cement composition on the values of the μ m and HVLs are investigated and discussed. In addition, the values of Z eff and N eff for all cement samples behaved similarly in the given photon energy range, and they decreased as the photon energy increased.

Analysis of the influence of the aluminosilicate sorbents on the immobilization of <sup>137</sup>Cs in the cement compound and its mechanical strength

Studies have been carried out to determine the main parameters characterizing the quality of cement compounds: 137Cs leaching rate and mechanical strength. As sorption additives, aluminosilicate sorbents were used, obtained from clay-salt slimes of JSC “Belaruskali” as a result of water and acid-water treatment to increase the content of the clay mineral illite, which is the main component in the composition of aluminosilicate sorbents. Model aqueous solutions of 137Cs were used as liquid radioactive waste, including those with a NaNO3 content of 150 g/dm . It has been established that the use of aluminosilicate sorbents makes it possible to reduce the rate of 137Cs leaching from cement compounds, which indicates a higher degree of 137Cs fixation in the matrix material compared to samples of cement compounds without sorption additives. The efficiency of the aluminosilicate sorbent for 137Cs immobilization during cementation of a model solution of liquid radioactive waste is 3 times higher than the well-known and widely used sorption additive (bentonite clay from the 10th Khutor deposit, Khakassia, Russia). Determination of the mechanical strength of samples of cement compounds with the addition of 5–15 % aluminosilicate sorbents showed that this indicator is 8–9 times higher than the standard value (4.9 MPa). The optimal dose of a sorption additive is 5–10 wt.% of the weight of Portland cement, which does not cause a significant decrease in the strength of the cement compound compared to a compound without the use of an additive and, at the same time, will provide a high level of 137Cs immobilization. The obtained research results indicate the prospects of using the developed aluminosilicate sorbents as a sorption additive for 137Cs immobilization when handling liquid radioactive waste.

The Effect of Waste Marble Dust and Corncob Ash on the Engineering and Micro-Structural Properties of Expansive Soil for Use in Road Subgrades

This research investigated the effect of Waste Marble Dust (WMD) and Corncob Ash (CCA) on expansive soil's engineering and microstructural properties. Various laboratory experiments were performed on the natural soil to ascertain its characteristics. The corncobs underwent pre-water treatment for fourteen days to remove excess potassium and increase their silica content, resulting in a rise in the silica level from 0% to 50%. At first, only WMD was added to the soil in increments of 5% to 30% using compaction and California bearing tests. The optimum dosage of 15% WMD addition yielded the best result. CCA was then incorporated by the weight of the soil from 2% to 10% in increments of 2% to the first optimum (15% WMD) to obtain the overall optimum for the study (15% WMD and 8% CCA). Stabilization of the natural soil using both materials led to the modification and solidification of the soil mass, evident by the rise in California bearing ratio values from 1.68% to 15.53% and unconfined compressive strength from 41.33 kN/m2 to 174.68 kN/m2. There was also a decrease in the soil's free swell from 120% to 15% as well as reductions in the liquid limits from 56.23% to 36.01% and in the plasticity index from 29.74% to 8.72%, respectively. The microstructural images showed the formation of cementitious compounds in the form of calcium silicate hydrate and calcium aluminate hydrate gels. The findings indicate that using WMD and CCA as a unit has great potential in enhancing engineering properties, like strength parameters and the swell potential of expansive soils.

Sulphate-based activation of a binary and ternary hybrid cement with portland cement and different pozzolans

The purpose of this study was the development of a hybrid cement based on ordinary Portland cement (OPC) and different sulfate-based alkaline activated pozzolans using the one-part method dosed in binary and ternary mixtures. The factors evaluated were the percentage and type of pozzolan between fly ash, tepojal and volcanic sand and the use of alkaline activators between sodium and potassium sulfate. The amount of cement in conjunction with the use of alkaline activators benefits the reaction of the pozzolans, reducing the setting time according to isothermal calorimetry due to the consumption of portlandite when reacting with the pozzolans, which can be observed with the derivative of thermogravimetry at approximately 450°C. The shift of the main peaks in FTIR implies the reaction of the cementitious compounds towards the thermodynamically stable phase of C-A-S-H. The ternary mixture of OPC-Fly Ash-Tepojal/Volcanic Sand activated with 4% sodium sulfate are presented as the dosages with the best mechanical performance based on compressive strength due to a synergy effect between pozzolans. Tepojal and volcanic sand are chemically and physically presented as an eco-efficient alternative to natural pozzolan for use as cementitious material.

Environmental – Solar thermal effects a long-term on the efficiency of amorphous climate-resilient mortar using a central composite design application

The objective of this investigation is to evaluate the durability of dune sand mortar containing display e-glass waste (DEGW) in severe Saharan environments, chemical attacks, or other factors that can cause cementitious materials to deteriorate at long- term. The aim is to use DEGW powder as a partial replacement for dune sand in various mortar mixtures and assess the performance of hardened mortar in terms of ultrasonic pulse velocity, dynamic elasticity modulus, compressive strength, and flexural strength and sportivity. The study also examines the influence of the curing period and different climatic conditions in curing environments, such as those in Algeria's Sahara region. The Response Surface Methodology (RSM) was used to adjust the e-waste glassy mortar, with the statistical tool Central Composite Design (CCD) approach. The hydration of cement compounds was monitored using differential thermal analysis (DTA), thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), and X-ray diffraction (XRD). The DEGW was replaced in 5% increments from 0% to 20%. The results showed that the glassy dune sand mortar exhibited the highest properties at 20% incorporation after 365 days of severe climatic conditions. The feasibility of the proposed quadratic model was recommended for the five responses by RSM, in which the coefficient of determination (R2) ranges from 0.93 to 0.97, showing the model’s high significance. For structural display e-glassy dune sand mortar, display glass E-waste can replace 20% of dune sand, which improves all durability and environmental sustainability. Furthermore, the DSC, TGA / DTA results and XRD analysis showed that the < 0.08 mm class exhibited good pozzolanic behaviour, and the specimens significantly improved as curing periods increased.

Effect of material quality on cemented sand and gravel (CSG) dam slope design of Cibeet

The construction of the Cibeet Dam is crucial to mitigate downstream flooding in the Citarum River. Initially planned as an embankment dam with a 1:3.50 upstream slope, a 1:30 downstream slope, and a height of 47 meters, challenges arose due to foundation and earthquake considerations. The excessive requirement of embankment material at the dam site, which was insufficiently available, prompted the exploration of a more resource-efficient alternative. Consequently, a slimmer type of dam, specifically a Cemented Sand and Gravel (CSG) dam, was deemed necessary. The CSG dam, designed with minimal cement (80 kg/m3) and a mixture of sand and gravel (105.5 kg/m3), boasts a more upright slope, reducing material demand. This research examines the impact of material quality on the CSG dam slope. The finite element method assesses the dam’s stability using dynamic seismic forces. To achieve a stable dam slope design with existing materials, an extensive analysis was conducted on various slopes upstream and downstream, ranging from 1:0.70 to 1:1.20. The results indicate that a slope of 1:1.10 with a cement compound of 105.5 kg/m3 offers optimal stability. Implementing the CSG Dam effectively minimizes material requirements, mitigating the need for excessive exploration of material supplies.

Investigation of geotechnical and microstructure characteristics of gypsum soil using ground granulated blast-furnace slag (GGBS), fly ash, and lime

This study investigates the synergistic effects of Ground Granulated Blast-furnace Slag (GGBS), lime, and fly ash on improving the geotechnical properties of gypsum soil. Gypsum soil samples, constituting 84% of the mixture, were blended with lime and GGBS in proportions ranging from 0% to 16%. These mixtures underwent curing for 1, 7, 14, 28, 56, and 90 days. Tests and analytical techniques elucidated mechanisms responsible for strength improvements. Findings revealed that when fly ash was used alone, there was no significant increase in Uniaxial Compressive Strength (UCS). However, fly ash expedited essential pozzolanic reactions for silicate gel formation. The most substantial increase in UCS occurred in the 28-day samples, contrasting with lower gains in the 7, 14, 56, and 90-day periods. Enhanced strength in lime-GGBS-gypsum soil mixtures before 28 days was attributed to cation exchange and initial flocculation. In the 28-day specimens, increased strength was linked to ettringite crystal and silica gel growth. Microstructural analysis confirmed Ettringite (E) crystal growth within inter-crystalline and pore spaces. Cementitious compounds like CH, CSHH, CHS, CAH, and CASH displayed growth. The rearrangement of the clay mineral matrix, coupled with added sulfate, contributed to enhanced gypsum soil strength. Interestingly, decreased UCS in 56-day samples indicated increased ettringite crystal growth, resulting in reduced strength. Elemental analysis through Energy-dispersive spectroscopy (EDS) revealed shifts in Al: Si, Ca: Si, and Al: Ca ratios. The Al: Si ratio reduction confirmed the formation of more cementitious compounds in 90-day samples. Additionally, the Al: Si ratio in 28-day cured samples exhibited a significant decrease, signifying accelerated initial strength in lime and GGBS mixtures. The presence of sulfur (S) confirmed ettringite crystal formation, underscoring the intricate interplay between additives and curing durations, shedding light on mechanisms enhancing gypsum soil's geotechnical properties.

Study on Material Design, Performance, and Practical Application of Electrically Conductive Cement Compound

Electrically conductive cementations composite has several advantageswhich include strain sensitivity and high conductivity (ECCC). The ECCC can also perform the role of a conductivity sensor in a safety system that monitors the health of a building. Understanding and predicting electrical resistivity as well as compressive stress are necessary when using ECCC (UCS). In this study, we developed ECCC using three conductivity fillers: waste steel slag (SS), graphite powder (GB), and near - field ground blast furnace slag (GGBS) (GGPS). By adjusting the concentrations of the three conductive fillers, cement, and curing age, we created 81 different mix ratio for the UCS test and 108 different concrete ratios for the conductivity test. Sandier soils are best for using ordinary Portland cement (OPC), which is frequently utilised for stabilising purposes. In a rotating kiln, unusual and local building materials like clay or other silicates are heated to high temperatures (&gt;1500°C) to create Portland cement. Sandier soils are best for using ordinary Portland cement (OPC), which is frequently utilised for stabilising purposes. In a rotating kiln, unusual and local building materials like clay or other silicates are heated to high temperatures (&gt;1500°C) to create Portland cement. Slag is a commercial waste product produced during the steelmaking process. At various phases of the steelmaking process, slag from both the electric arc furnace and the ladle furnace is produced in electric arc furnaces and refining ladle furnaces, respectively. A byproduct of blast furnaces used to manufacture iron, GGBS is a cementing ingredient mostly used in concrete. Between 1972 and 1976, the Battelle Memorial Institute in Geneva founded the Program in Science and Human Affairs to conduct research and address complex, interconnected concerns. DEMATEL is one of the decision-makers with a number of criteria. DEMATEL technique is frequently used to extract a difficult problem's complex structure. DEMATEL's goal is to scale from a complex system and the link between causal factors in order to describe the system's perceptible organisational structure. The cause and effect link between the criteria is evident while evaluating complexity. According to the results, ordinary Portland cement (OPC) has the highest ranking, while graphite powder (GP) has the lowest ranking. Resulting in ordinary Portland cement (OPC) ranked first, graphite powder (GP) has low rank.

A novel citric acid-modified magnesium oxysulfide cement for the preservation of weathered sandstone relics

Due to the relatively low mechanical strength and high porosity, sandstone cultural relics show poor resistance to weathering and are vulnerable to significant deterioration. In this work, for the first time, a novel inorganic cementitious compound was introduced for sandstone preservation by combining magnesium oxysulfide (MOS) cement with citric acid (CA). Accordingly, the effect of CA on MOS cement was investigated in terms of mechanical properties, phase analyses, micropore structures, and microtopography. MOS cement with 0.5 % (wt.) CA exhibited the best performance, with excellent infinite compressive strength (20.92 MPa) and softening coefficient (125.06 %). Due to the CA addition, the X-ray diffraction (XRD) analysis represented the remarkable appearance of the 5 Mg(OH)2·MgSO4·7H2O (5-1-7 phase), the primary strength-contributing phase in MOS cement. Furthermore, the investigations on MOS mortar (mixing MOS cement with silica sand) showed that MOS cement effectively functioned as a binder for silica sand. Finally, the excellent compatibility between the MOS cement and sandstone particles highlighted the feasibility of the cement as a novel material for sandstone preservation. These findings demonstrated the MOS's promising role in sandstone cultural relics conservation with significant potential.

Damage constitutive model of fly ash–cementitious iron tailings powder under small strain

With the vigorous development of industrial economy, the production capacity and level have been significantly improved, but at the same time, a large amount of iron tailings, fly ash and a series of bulk solid waste materials have been accumulated. These industrial wastes have caused serious impact on the ecological environment. How to deal with them effectively is an urgent problem that needs to be solved. The aim of this study was to investigate the effect of cement and fly ash compound admixtures on the mechanical properties of iron tailings powder (ITP). Hence, different mixing ratios of cement and fly ash were used to prepare two kinds of ITP-based materials. A range of uniaxial compressive strength (UCS), resonance column (RC), scanning electron microscopy and X-ray diffraction tests were conducted to investigate the roles of cement, fly ash and curing age in ITP solidification. A random one-dimensional damage model was imported to study the damage evolution of ITP materials using the UCS and RC test results, which showed that cement and fly ash enhanced the unconfined compression strength and small-strain stiffness of ITP. When 5–10% fly ash content was used as a substitute for 10% cement, the unconfined compressive strength and small-strain modulus of cement–fly ash–ITP increased with curing age. The microstructure and mineralogy analysis confirmed that fly ash enhanced the strength of the material. Overall, the damage constitutive model effectively represented the randomness of the compressive strength and stress–strain relationship of ITP materials under unconfined conditions.

System "dispersed polyvinyl acetate-calcium silicate" in furnishing materials

This article focuses on the processes of interaction between calcium silicate hydrates and dispersed polyvinyl acetate in tight films with the aim of developing compounds meant for restoration and finishing works. The basis of this development relies on the concept concerning the determining role of the crystal-chemical factor of the silicate phase in the formation of organic-mineral compounds of increased durability. The characteristics of dispersed calcium silicate hydrates are portrayed. The preparation conditions, accounting for the synthesis of the product of submicrocrystalline structure, conforming with the stoichiometry CaO:SiO2=0.8-2.0 have been determined. The interaction has been studied for compounds achieved by mixing ingredients in a rapid whirling mixer, and subjected to hardening at T=20+2 °C. With the aid of XRD, DTA and Infra-Red Spectrometry methods the formation process of the sophisticated polymer silicate phase in the material was observed for a period of 90 days. The properties of the film were investigated and its high resistance against the influence of external factors was established. On this basis a conclusion concerning the quite high effectiveness of substituting portland cement with dispersed calcium silicate hydrate in polymer cement compounds has been made White colour and other various special properties determine the suitability for repair and finishing works on facades of buildings.

Study on improving properties of desulfurized gypsum based cementitious materials

Two kinds of inorganic reinforcing materials, single Portland cement clinker, compound Portland cement clinker and mineral powder, were used to analyze the effects of desulfurized gypsum on the properties of desulfurized gypsum based cementation material. The results show that either single Portland cement clinker or compound Portland cement clinker and mineral powder can effectively improve the mechanical properties and softening coefficient of the material, and the effect of compound mixing is better. The optimum dosage of Portland cement clinker is 10%, the 7d and 28d bending strength of cementing material is 2.5MPa and 4.1MPa, the compressive strength is 4.6MPa and 9.8MPa, and the softening coefficient is 0.61. The appropriate composite content of Portland cement clinker and mineral powder is: Portland cement clinker 5%~10%, mineral powder 10%~15%, gelling material 7d, 28d bending strength of 3.0~3.5MPa, 6.3~7.4MPa, compressive strength of 5.4~6.7MPa, 12.1~13.6MPa, softening coefficient of 0.58~0.62.

Effect of the waste ornamental rocks on the hydration and life cycle of Portland cement composites

The production (extraction, cutting and polishing) of ornamental rocks generates a high volume of waste (abrasive slurry) which, when dry, generates a fine powder. The main impacts generated by the inadequate disposal of these residues are the contamination of the soil and the water table, alteration of the biological chain of living beings and siltation of rivers. Few studies analyze the influence of mud heterogeneity on the hydration of cementitious composites. In this context, this work aimed to evaluate the effect of the characteristics (chemical, physical and mineral) of waste from wet processing in ornamental rock plants (marble, granite, slate, among others) of different origins on the hydration process, performance and life cycle of composite with 20% replacement of Portland cement. Heterogeneity was evaluated by chemical composition, mineralogical and physical characteristics of the waste. The reactivity of the residue was determined in the Chapelle Modified test, Thermogravimetric analysis, and expansion test by Le Chatelier needles. The evolution of hydration was studied in pastes by evaluating the setting time and using the differential scanning calorimetry test. The mortars were characterized for consistency, porosity, and compressive strength. The results indicated that the residues show considerable heterogeneity. However, this does not influence the analyzed properties of the cementitious compounds. The high reduction in axial compressive strength indicates the use of these residues in lower contents or indication of this cement with this residue for non-structural purposes. It was concluded that the filer feat accelerated the hydration reactions in a similar way to the cement removed from the mixture.

Laboratory and modelling investigation on chemically stabilized native expansive soil as a CNS material

Expansive soils challenge the stability of several civil engineering structures. Because of the presence of Montmorillonite clay mineral, they have the inherent property of swelling and shrinking upon wetting and drying. Researchers proposed several ground improvement and foundation techniques to enchase the properties of these soils. Cushion materials, particularly Cohesive Non– Swelling (CNS) cushions, attracted the attention of civil engineers due to their simplicity and long-term stability. To avoid the problem of the non-availability of required soil, a technique is presented in this study to convert local expansive soils into suitable CNS materials via chemical stabilisation. The study uses clayey sand from the Tirupati region of Andhra Pradesh. Admixtures such as fly ash and lime chemically modify native soils into CNS materials. The effectiveness of these prepared CNS materials in reducing expansive soil heave is investigated using model test tanks. SEM and XRD analyses are also used to determine changes in soil microstructure. According to the findings, 5% lime and 20% fly ash are optimal for preparing CNS material. The microstructure of the stabilised soil revealed the formation of cementation compounds, which improved the strength of the native soil stabilization using fly ash.

Analysis of the phases and functions of the various compounds of calcium sulfoaluminate cement after exposure to high temperature

High temperature (HT) in-situ XRD method was adopted to investigate the calcium sulfoaluminate cement (CSA) or C4A3$ crystal architecture as well as its phases when passing through the temperature range of 20° to 70 °C. We examined the particle size analysis of the CSA ground powder when heated to different temperature (e.g., 35, 50, and 70 °C) in correlation with the HT X-ray diffraction (HT XRD) pattern as well with the compressive strength. The particle size of the lattice parameters increased during heating. The architecture transformation phase of the CSA took place at 50 °C. The transformation of the crystal cubic structure phase of the C4A3$ when passing from orthogonal to cubic space group was unstable with more heating (70 °C) and was adjustable. The C4A3$ compound's orthogonal and cubic crystal structures were clearly identified. The crystal structures were found to be responsible for the dehydration that occurred as the temperature rose and also for the decrease in compressive strength. The obtained final products of the C4A3$ were in cubic and orthogonal forms. The exothermic form of the C4A3$ was mostly observed at 20 °C and at 35 °C. The AFt and AFm crystal structure framework was constituted of AlO6 (in octahedral form) and AlO4 (in tetrahedral form).