Compressive Strength Of Cement Paste Research Articles

Wet carbonation of recycled cement paste powder using a CO2-loaded monoethanolamine solvent as an internal CO2 source

To address the challenge posed by the carbonation product layer formed on recycled cement paste powder (RCPP) on the efficiency and degree of carbonation, CO2-loaded monoethanolamine (MEA) “microcapsules” were used. The CO2 within MEA was released by heating after the formation of the dense carbonation products layer on RCPP to provide an additional internal CO2 source to penetrate into the uncarbonated layer. Results showed that using CO2 dissolved in 15 %, 30 %, and 45 % MEA aqueous solution increased the carbonation degree of RCPP by 10.8 %, 11.2 %, and 13.8 %, respectively, compared to RCPP wet carbonated in water. In addition to calcite, vaterite and aragonite were observed in the CO2-loaded MEA carbonated RCPP. The long-term compressive strength of cement pastes with 30 % CO2-loaded MEA carbonated RCPP increased, and the porosity decreased compared to cement paste with RCPP wet carbonated in water. However, MEA negatively affected the early compressive strength of the cement paste.

Influence of magnesite/limestone addition on the hydration characteristics of ternary slag cement systems

To explore the potential of magnesite adopted as supplementary cementitious material (SCM) in cement industry, the authors of this paper investigated the hydration characteristics of ternary slag cement mixtures containing magnesite or limestone. All cement pastes were formulated with a water-to-binder ratio of 0.4, and a total of 50 % substitution level was applied across the blends, with varying slag and magnesite/limestone contents. Experimental results confirmed that adding limestone to slag cement can promote the hydration of cement clinker through the nucleation effect, while not for magnesite addition. As the substitution ratio of magnesite increased, there was a notable increase in both the critical pore diameter and cumulative pore volume, leading to a continuous decrease in the compressive strength of cement pastes. Compared to limestone-containing blends, the incorporation of magnesite was more beneficial to the compressive strength at 7 and 28 days. Additionally, limestone facilitated the precipitation of hemi- and mono-carboaluminate, whereas no hemicarbonate was observed in mixtures containing magnesite. The addition of magnesite promoted the formation of hydrotalcite-like phase, and the quantitative analysis revealed that the dissolution of magnesite primarily occurred in the first 7 days. The authors believed that the results obtained in this paper proposed new perspectives on utilizing magnesite as SCM in cement industry.

Target dispersion of pozzolanic materials nearby hydration-released calcium hydrates to improve the pozzolanic reaction degree

The random distribution of pozzolanic materials (PM) using direct mixing strategy reduces their contact possibility with hydration-released calcium hydroxide (CH), and limits the corresponding reinforcing efficiency to cement-based materials via pozzolanic reaction. In this study, a target dispersion strategy of PM nearby CH was proposed using super absorbent polymers (SAPs) as the carrier. On the one hand, nano silica (NS) and calcined clay (CC), two typical PM, can be encapsulated into SAPs through the hydrogen bonding interaction; on the other hand, the region around SAPs was enriched with more water and higher Ca2+ concentration, which triggered the in situ crystallization of CH. In this case, the contact possibility between the NS or CC (NS/CC) and hydration-released CH was improved by the target dispersion strategy, and resulted in a 60% ∼ 253% increase in pozzolanic reaction degree (PRD) of NS/CC. Furthermore, the reinforcing effect of NS/CC on compressive strength of cement paste was enhanced by 25% through this strategy. Therefore, the current study introduces a novel method for increasing the pozzolanic reinforcing efficiency of cement-based materials by turning the random to target dispersion of PM nearby CH.

Assessment of blended cement containing waste basalt powder: physicomechanical and electrochemical impedance spectroscopy investigations

Basalt powder (BP) is the residue of a plant that crushes basalt stones. This work deals with the effect of waste BP on the properties of cement mortars and the physical properties of hardened mortars. Modified concrete was prepared by partial replacement of BP in amount of 5, 10, 20% by weight of cement. Physico-mechanical properties and corrosion resistance were investigated. Electrochemical impedance spectroscopy (EIS) was used to examine the corrosion behavior of cement pastes with a partial addition of basalt powder in aggressive solutions of 5% NaCl and 5% MgCl2 for up to 270 days. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed to investigate the hydration process and microstructure formation of the basalt blended paste. Results indicate that the addition of basalt powder as a partial replacement of cement influences the microstructure of the interfacial transition zone (ITZ), which is denser and stronger than in cement paste without basalt powder. The filler effect of the basalt powder improves the compressive strength of cement paste. Also, comparing BP0 and BP20 in 5% NaCl after 270 days, the partial substitution of cement with BP resulted in a higher compressive strength of 671 and 895 kg/cm2, respectively. The EIS results also showed the highest values of Rp 953 ohms cm2 after 270 days. This high corrosion resistance might indicate the binding by high Al2O3 that reduced the free aggressive chloride ions in the solution.

A new hypothesis for full stage deformation of cement-based materials mixed with MgO expansive agent: Generation and filling of cavity

MgO expansive agent (MEA) is an effective admixture for compensating for shrinkage and minimizing cracking in concrete. This study reexamined prevailing explanations of its expansion mechanism, with a particular focus on the synergetic influence on early-age compressive strength. Full-stage deformations and compressive strength of cement pastes with different reactivities and dosages of MEAs were investigated. Four deformation stages were uncovered, and the correlation among deformations and pore structures was systematically analyzed from the standpoint of expansion driving forces. Particular attention was given to the generation of cavity and swelling pressure due to the unique physicochemical properties of fine brucite for water adsorption. Swelling pressure was used to explain the sharp increase in expansion and decrease in strength of cement pastes at early ages, and crystallization pressure was used to account for shrinkage compensation and strength enhancement of MEA at late ages. A new hypothesis, based on the generation and filling process of cavity varying with the reactivity and dosage of MEA, was proposed to describe the expansion mechanism of cement pastes mixed with MEA.

Acceleration of chelator on mineralization reaction of cement paste at different CO2 pressures

In order to further improve the mechanical properties of CO2-cured cement paste, effects of chelator on the compressive strength of cement paste cured under different CO2 pressures were investigated, and the mechanism of chelator in accelerating the mineralization reaction was deduced from the analysis of the degree of mineralization reaction, microstructures, and phase compositions, with the contribution of chelator in reducing the net CO2 emissions of cement industry being evaluated. The results showed that the use of chelator could significantly enhance the compressive strength of cement paste cured at different CO2 pressures compared with other methods for improving the compressive strength of CO2-cured cement paste, and the compressive strength of cement paste cured for 48 h at 0.1 MPa and 0.4 MPa CO2 could be enhanced by 23.2 % and 9.4 %, respectively. Chelator could migrate Ca2+ from smaller pores and pore channels to larger pores, decreasing the Ca2+ content and degree of mineralization reaction in smaller pores and pore channels, avoiding the blockage of the stomata by generated CaCO3, and allowing more CO2 to penetrate and diffuse into the cement paste, thereby promoting mineralization reaction and significantly improving compressive strength of cement paste cured at atmospheric pressure. The use of chelator in mineralization curing cement-based materials could further reduce net CO2 emissions from cement production, making significant contribution to the advancement of mineralization curing technology and environmental sustainability.

Machine learning for predicting compressive strength of sustainable cement paste incorporating copper mine tailings as supplementary cementitious materials

Copper mining produces significant amounts of copper mine tailings (CMT), necessitating appropriate waste handling and disposal practices. By substituting a portion of cement with CMT as supplementary cementitious materials (SCMs), we aim to address two environmental issues simultaneously: reducing copper mine waste in landfills and decreasing embodied carbon by using less cement. The exploration of CMT recycling as a cement replacement requires evaluation of its impact on material performance, such as compressive strength. In this paper, we address this by machine learning that features data fusion of large public data with our own small data on compressive strength of CMT-incorporated cement. We developed and critically evaluated three machine learning models: a simple linear model, Gaussian process, and random forest that predict the compressive strength of CMT-incorporated cement pastes with different mix designs (e.g., varying amounts of CMT and water-binder ratios) and curing ages. Hyperparameters in the random forest model were tuned using Bayesian optimization. Following a comprehensive evaluation of the models, we find that the random forest model can accurately estimate the compressive strength of cement paste across the mix designs. Furthermore, results from SHapley Additive exPlanation (SHAP), Individual Conditional Expectation (ICE), and Partial Dependence Plots (PDP) revealed that cement, ground-granulated blast furnace slag, superplasticizers, and curing ages positively influence compressive strength. This study contributes to acceleration of sustainable material technology to obtain the best mix design and desired compressive strength.

The influence of multi-scale tough liquid fiber toughening agent on the mechanical properties of oil well cement-based composite materials

Cementing is a key process in drilling engineering, and the cement sheath in cementing can sometime have problems such as significant brittleness, low toughness, and low resistance to impact damage, especially in perforation and fracturing environments where the cement sheath is more susceptible to damage. In response to the above issues, three types of inorganic carbon fibers, including 1 mm carbon fiber, 2 mm carbon fiber, and nanocarbon fiber, were studied indoors to investigate the influence of their ratios on the mechanical properties of cement paste. The optimal mixture of 1 mm carbon fiber, 2 mm carbon fiber, and nanocarbon fiber in a ratio of 3:2:1 was selected, and a multi-scale liquid fiber toughening agent BS-54 was obtained through special liquefaction process treatment. The liquid fiber toughening agent BS-54 has good water dispersibility and can evenly disperse in the slurry water, effectively improving the dispersion and addition of multi-scale fibers in cement slurry. The cement slurry prepared with multi-scale dispersed liquid fiber toughening agent has good rheological properties, water loss, and thickening properties. The addition of multi-scale dispersed liquid fiber toughening agent to cement slurry significantly increases the tensile strength, impact strength, and compressive strength of cement paste, effectively reduces the elastic modulus of cement paste, improves the strength of cement paste, and achieves toughening effect. Microscopic analysis shows that the active nanoparticles dispersed by multi-scale dispersed liquid fiber toughening agents can interweave between gaps, and the dense cross-linked structure formed by their multi-scale micro nano structure improves the toughness and strength of cement slurry. Moreover, the multi-scale dispersed liquid fiber toughening agent cement slurry ensures that the cement stone sample has good integrity under external impact, which is conducive to improving the impact resistance of the cement stone.

Effects of Noncrosslinked Polyvinyl Alcohol Fluid Loss Additive on the Compressive Strength and Viscosity of Class G Cement Slurries

Summary Limiting the fluid loss from the cement slurry to the adjacent formation by using additives is essential for maintaining the slurry’s water/cement ratio. The present work focuses on the effect of noncrosslinked polyvinyl alcohol additive (PVOH), a widely used fluid loss additive (FLA), on the compression strength and rheological behavior of Class G cement pastes. Results of the current study show that the PVOH surfactant characteristic and its absorptive mechanism interfere not only with the hydration process but also with the physical properties and compressive strength of cement pastes, such as porosity, permeability, and early age strength, which revealed the importance of using a defoamer when PVOH is present in the mixture. In the absence of a defoamer, the PVOH additive generates foam in the mixed cement paste samples, which results in increased porosity and reduced compressive strength of the hardened cement paste. Moreover, regarding rheology, increasing the PVOH concentration increased the effective viscosity when evaluating flow curves. Therefore, this study demonstrates a systematic method for assessing the possible effects of cement paste additives, such as PVOH and defoamer, providing a physical and mechanical approach rather than just chemical to evaluate additives’ influence on the mixtures. This method should consider different additives in combination with PVOH to test cement paste stability and to obtain specific working recipes.

Role of C-F-S-H/PCE nanocomposites on the hydration of Portland cement with varying gypsum levels

This study delves into the role of C-F-S-H/PCE (calcium-ferrite-silicate-hydrates/polycarboxylate ether) nanocomposites on the cement hydration with varying gypsum levels. It is found that the addition of C-F-S-H/PCE nanocomposites simultaneously promotes the dissolution of cement clinker and gypsum during early hydration. What’ more, the early hydration is further enhanced notably by C-F-S-H/PCE nanocomposites at moderately higher gypsum level without compromising the long-term compressive strength. It merits attention that the compressive strength of cement paste emerges as a factor intricately interwoven with not only its microstructure but also the content of AFt (ettringite) it harbors. Anyway, in the presence of the C-F-S-H/PCE nanocomposites, the faster depletion of gypsum leads to an earlier formation of AFm (monosulfoaluminate) whereas the morphologies of various hydration products remain unaffected. The findings demonstrate that the addition of C-F-S-H/PCE nanocomposites increases the demand for gypsum in cement and provide insights into the production of cement and concrete using seeding materials.

Comparison between Four-Probe and Two-Probe Electrical Resistivity Measurement to Monitor the Curing and Piezoresistivity Behavior of Smart Cement Paste Modified with Waste Steel Slag and Green Nano-magnetite

Abstract This study aims to examine the compressive strength, electrical resistivity, and piezoresistivity characteristics of ordinary Portland cement (OPC) with a constant water-to-cement ratio (w/c) of 0.38. The optimal value of steel slag (SS) was determined to be 5 % based on the compressive strength of six different mixes of cement paste modified with various SS from 0 % to 30 % weight of cement. Additionally, the investigation will include modified cement samples containing 1 % green synthesized material and commercially available nano-magnetite (NM). Because iron is the primary component of SS and NM, the electrical resistivity, which is the primary criterion for structural health monitoring of cementitious material, can be increased by adding SS and NM. Hence, a comparative analysis was conducted to assess the resistivity of cement paste throughout the early curing period up to 28 days using an alternative current (AC) and embedding wires into the specimen, employing both the two-probe (2P) and four-probe (4P) methodologies. The findings suggest that the 4P method is a more precise approach for determining electrical resistivity than the 2P method, as the wire probe is not considered in the 4P method. Hence, it is imperative to compute the correlation between the 2P and 4P methodologies in order to attain a precise resistivity measurement. The suggested model indicates that the expected 4P resistivity can be measured with high precision, a high coefficient of determination (R2) of .97, and a low root mean square error (RMSE) of 7.33 Ω·m, based on the 2P result. The piezoresistivity results demonstrated that the cement paste modified with green synthesis nano-magnetite (GSNM) had a higher electrical resistivity (ER) change, 10.85 % greater than cement paste only, 57 % higher than cement modified with SS, and 34.2 % higher than cement paste modified with commercial nano-magnetite (CNM) after 28 days of curing. In addition, the compressive strength of cement paste modified with GSNM was higher than that of cement paste, cement paste modified with SS, and cement paste modified with CNM by 15.96 %, 21 %, and 1.7 %, respectively, after 28 days of curing. A Vipulanandan p–q model was used to forecast the electrical resistivity of cement paste versus time at start hydration during 28 days of curing and the change of electrical resistivity versus compressive strength at 3, 7, and 28 days. The Vipulananda p–q model anticipated both electrical resistivity and piezoresistivity behavior well.

Algal Biochar-Metal Nanocomposite Particles Tailor the Hydration Kinetics and Compressive Strength of Portland Cement Paste.

Biochar can improve the mechanical properties of portland cement paste and concrete. In this work, we produced algal biochar-zinc (biochar-Zn) and algal biochar-calcium (biochar-Ca) nanocomposite particles and studied their effect on the hydration kinetics and compressive strength of cement paste. Results show that 3 wt % biochar-Zn delayed peak heat evolution during cement hydration from 8.3 to 10.0 h, while 3 wt % addition of biochar-Ca induced a minor acceleration of peak heat from 8.3 to 8.2 h. Both biochar-Zn and biochar-Ca nanocomposite particles increased the compressive strength of cement paste at 28 days by 22.6 and 17.0%, respectively. Data substantiate that retardation or minor acceleration of the reaction kinetics was due exclusively to the presence of Zn and Ca phases, respectively, while the enhanced strength was attributed to a nucleation effect induced by such phases and the internal curing effect of biochar.

Effect of Superabsorbent Polymer (SAP) Size on Microstructure and Compressive Strength of Concrete.

Superabsorbent polymers (SAPs) are hydrophilic, polymeric network materials renowned for their ability to enhance various properties of cementitious materials. This investigation examines the impact of SAP size on the hydration degree, porosity, and compressive strength of cement pastes and concrete under diverse curing conditions and ageing periods. The findings reveal that SAP addition stimulates the hydration of the C2S phase, particularly during the early curing stages, thereby favouring early strength development. However, the effect of SAPs on hydration promotion diminishes as their size increases. Conversely, the size of SAPs affects the hydration range of their action, and the 400 µm SAP demonstrates the most extensive range of hydration enhancement, reaching up to 105 µm. Additionally, SAPs effectively reduce porosity in small pores (4 nm-10 μm), with 200 μm and 400 μm SAPs exhibiting the highest efficacy. While analysing the effects of SAPs on larger pores (>10 μm), the results show that although larger SAPs result in larger average porosity, the total porosity is effectively reduced, particularly in samples incorporating 400 μm SAP. The compressive strength of cement paste, even after 28 days, is slightly reduced following the introduction of SAPs. However, the strength of concrete, due to the naturally occurring pores eliminating the negative effects of the pores produced by SAPs, is significantly increased following the introduction of SAPs, especially 400 µm SAP.

The influence of silica-coated nanoscale titanium dioxide on the microstructure, mechanical properties, and carbonation resistance of cementitious materials

Nanomaterials possess great application prospects in improving the performance of cementitious materials. However, their high agglomeration hinders their efficient utilization in cementitious matrices. Consequently, surface modification has recently attracted attention as a method to enhance dispersibility. In this study, silica was employed to modify the surface of nanoscale titanium dioxide (NT), resulting in the synthesis of silica-coated nanoscale titanium dioxide (SCNT) composite material. In particular, the dispersibility of SCNT was investigated, and its influence on the compressive strength development of modified cement paste was analyzed. Additionally, the mechanisms affecting cement hydration behavior and microstructure evolution were comprehensively analyzed. Lastly, the impact of SCNT on the carbonation resistance of cementitious materials was further explored. Interestingly, the research results indicate that the surface SiO2 coating treatment improves the dispersibility of NT. More precisely, compared to 3 % NT, the addition of 3 % SCNT can increase the compressive strength of cement paste by 20.52 % at 3 days and 16.52 % at 28 days. Specifically, the incorporation of SCNT promotes cement hydration, refines the crystal size of Ca(OH)2, reduces the crystal orientation growth index of Ca(OH)2, and enhances the polymerization degree of calcium silicate hydrate (C-S-H), optimizing the pore structure. Furthermore, the 28-day permeability coefficient of 3 % SCNT mortar is reduced by 99.98 % compared to the blank group, effectively enhancing the carbonation resistance of cementitious materials. Overall, the findings of this study will contribute to the development of high-performance and multifunctional nanocomposite cementitious materials.

In-situ dispersion of nano-TiO2 to highly reinforce cement paste

Regardless of how good pre-dispersion of nano-TiO2 in aqueous solutions, re-aggregation rapidly occurs once it is mixed into fresh cement mixtures, limiting the nano-reinforcing efficiency for cement-based materials. In this study, an in-situ release strategy by pre-encapsulating nano-TiO2 in microscaled ice and post-dispersing into fresh cement matrix during ice-melting process was developed to highly reinforce the microstructure and properties of cement paste. Compared with the conventional dispersion strategy, a much better dispersion of nano-TiO2 (0.6 wt% by cement) was achieved using the in-situ release strategy, which not only improved the 7- and 28-day compressive strength of cement paste by 9.2% and 10.1%, respectively, but also reduced the cement hydration heat and water adsorption by 36.1% and 4.6%, respectively. In addition to this, the NO degradation efficiency of cement paste was also improved by 20% due to the larger exposed surface area of nano-TiO2 with better dispersion. These research outcomes demonstrate that the in-situ release strategy facilitates the dispersion of nano-TiO2 in cement matrix and contributes to highly reinforcing cement paste with lower hydration heat and water adsorption, strong mechanical strength and higher photocatalytic properties.

Internal curing with superabsorbent polymer modified by nano SiO2: Shrinkage mitigation and microstructure refinement

The existing commercial superabsorbent polymer (SAP) products have the intrinsic defects of low internal curing efficiency and weakening strength. In this paper, a novel type of organic-inorganic composite SAP (SAPN) modified by nano SiO2 was designed and synthesized. The absorption-desorption kinetics of SAP-N in alkali pore solution were measured to evaluate the structural stability and water retention capacity. The water transport process and distribution of SAP-N in cement pastes were studied using 1H NMR and X-ray computed tomography. In addition, the effect of SAP-N on the autogenous shrinkage, microstructure, and compressive strength of cement pastes was investigated. The research results demonstrated that the incorporation of nano SiO2 could enhance the absorption capacity of SAP in pore solution. The water retention capacity of SAP-N was increased by over 50 % compared to commercial SAPC, despite the dissolution of a proportion of nano SiO2. SAP-N exhibited a low agglomeration degree but a high effective utilization rate of internal curing water in cement pastes, and thus mitigated effectively the self-desiccation and autogenous shrinkage. The hydration degree of cement pastes internally cured with SAP-N was significantly enhanced owing to the pozzolanic effect of nano SiO2, which enabled the in-situ repair of residual voids and reduced capillary pore size, thus improving the long-term compressive strength.

Comparative study of nanomaterials activated recycled powders from demolition and decoration wastes as supplementary cementitious material

Powdered particles can significantly affect the technical performance of recycled aggregates and recycled concrete. Therefore, there has been a considerable focus on the disposal and utilization of recycled powder (RP) with high value. This study applied nano-CaCO3 (NC), nano–graphene oxide (GO) and nano–SiO2 (NS) to activate RP from demolition and decoration waste (RP1 and RP2, respectively). The results indicated that the nanomaterials had an activation effect on RP, but the effect was more pronounced for RP2. In addition, NC had the best activation effect on the RP among the three nanomaterials. Comparing to cement pastes with 30% RP2, compressive strength of cement paste activated by NC, GO, and NS were increased by 43.4%, 33.3% and 23.7% at 28d, respectively. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Scanning electronic microscopy (SEM), and mercury intrusion porosity (MIP) were utilized to further explore the activation mechanism. Results presented that nanomaterial activated RP could promote hydration degree to produce more Ca(OH)2 (CH), meanwhile, the nanomaterials activated RP refine and modified the orientation index of CH. This paper implies a useful activation method for RP, which is expected to fully stimulate the potential of RP to form new kinds of supplementary cementitious material.

Comparative study on the environmental impact of Portland cement paste that mixed with naphthalene or carboxylate based polymer solutions

The environmental impact is now a valuable coefficient for any human activity. The effect of solar UV radiation on the cement samples was limited and contained in the thin surface layer of the samples. In general, viscocrete was the most effective in protecting cement against solar ultraviolet radiation, where cement samples treated with the two polymers used separately showed greater compressive strength values than those recorded for samples treated with sikament polymer. This study is important since the mechanical properties of cement and concrete at early stages are important in the field of civil engineering. The effect of soaking in water on the ability of the cement to withstand the pressure on it was also studied, and several physical measurements were applied to samples of untreated cement and samples mixed with the mentioned polymers. These measurements included measuring the porosity, density, and total dissolved solids by X-ray diffraction, FTIR, and line scan EDX. These measurements were carried out on cement samples before, after, after soaking in water, as well as on cement samples mixed with polymers. The measurements were extended to the soaking water. So, adding two types of polymers (Sikament and Viscocrete) separately to cement could protect concrete constructions against serious environmental impacts. The EDX analysis of the samples used in this study showed that the Egyptian sources of raw materials used in the cement industry are rich sources of rare chemical elements. The importance of adding two types of polymers, Sikament and ViscoCrete, separately to cement protects concrete construction against environmental impacts, which is our main highlight, significance, and advice of this work. Decrease the water reduction percentage and increase the compressive strength for portend cement paste to 0.5 % viscocrete using 15 W and 30 W UV lamps, with a maximum value of 127.52 MPa for 0.5 % viscocrete at the 30 W lamp. Higher UV lamp exposure at 45-watt lamp decreases the compressive strength after exposure than others. The total porosity percentage of all used percentages of Sikament polymer addition is greater than that using viscocrete polymer with a 0.75 % Sikament high value of 7.60 (total porosity) TP%. The conductivity EC of the cement treated with polymer samples shows a smaller increase in the case of viscocrete polymer than that of Sikament, with a value of 404 uS using 0.5 % and 0.75 % viscocrete, which is supported by TdS measurements with values of 202 ppm for 0.5 % and 0.75 % viscocrete, respectively. The EDX results for cement polymer mixtures prove that both polymers used extract many elements from the cement paste and protect human beings from their dangers, like Sb, Na, Zr, Hf, Rb, Mo., Ti, P, Cu, Er, Cl, In, and Te,Te with greater efficiency for the Viscocrete polymer than the Sikament one. Many factors affecting the cement's compressive strength and mechanical properties are the innovation of this work, which deals with the impact of some materials affecting it. The main target is to discuss the effect of different polymers on some properties of cement paste. Other properties can be discussed in near future, like the void volume effect, packing density, Van der Waals volume, and apparent molar volumes. The polymer contents have the largest effect on increasing the compressive strength of cement paste, followed by the w/c ratio and curing time.

Mechanism study on the effect of diammonium hydrogen phosphate on the setting time and micro-nanostructure of ordinary Portland cement paste

The effect of diammonium hydrogen phosphate (DAP) on the setting time, mechanical properties and micro-nanostructure of cement paste is investigated. The results show that with an increase in DAP content, the peak value of hydration heat of cement is delayed, but the 3d cumulative hydration heat release of the cement is basically the same. The 3d compressive strength of cement paste is not significantly different, and the 28d compressive strength increases first and then decreases. When the DAP content is 0.5 wt%, the compressive strength of cement paste is most significantly improved, increasing by 38.5%. Meanwhile, the initial and final setting times of cement paste are extended by 74.0% and 73.2%, respectively. When the DAP content is 1.0 wt%, the cement paste has the longest setting time, with the initial and final setting times extended by 101.8% and 103.5%, respectively. However, the compressive strength of the cement paste can still be improved by 10.5%. It is mainly due to the change of pH value and calcium ion concentration of cement pore solution with different DAP content, which changes the micro-nanoscale morphology of C-S-H gel, Hamaker constant between globules, microscopic Young's modulus, and pore structure.

Valorization of Marble Waste Powder as a Replacement for Limestone in Clinker Production: Technical, Environmental and Economic Evaluation

This research combines technical, environmental, and economic aspects regarding the utilization of Bege Bahia marble waste (BB) in clinker production. Three different eco-friendly clinkers were produced, investigated, and compared with one that is commercially available. BB was used to replace 49.2%, 77%, and 80.3% of the limestone by total amount of clinker. Two clinkers were selected to produce cement pastes, and their impact on compressive strength at 28 days was examined. The results suggest that substituting limestone with BB does not adversely affect the compressive strength of cement paste. Moreover, employing 77% or 80.3% BB in clinker production does not significantly influence the alite and belite contents but slightly increases the tricalcium aluminate and ferrite phases while reducing the periclase content. A life cycle analysis was conducted to assess the effects of replacing limestone with marble waste. The results revealed a substantial decrease in abiotic depletion, leading to conservation of substantial natural resources. Consequently, the utilization of BB in clinker production makes a significant contribution to environmental preservation while providing an effective alternative to limestone. In addition, the resulting clinkers serve as useful repositories, providing a permanent and sustainable destination for waste that is currently deposited in landfills. Finally, the economic viability was also examined under various scenarios based on the distance between marble and cement plants. The results highlight the transport distance of marble waste as the primary determinant of economic feasibility in utilizing this residue as a limestone replacement.