Ordinary Portland Cement Paste Research Articles

Application of Impedance Spectroscopy in the Study of Aluminium Alloy 1100 in Cement Pastes

In the context of an investigation of the corrosion inhibition effect of LiNO3 and Li2CO3 on Aluminium Alloy 1100 embedded in ordinary Portland cement pastes, Electrochemical Impedance Spectroscopy (EIS) technique was used to gain information on the corrosion rate and mechanism.In parallel to the corrosion property analysis, information on the porosity of the cement paste matrix could be retrieved from EIS. This was realised by an innovative methodology combining the equivalent circuit model fitting the EIS curves with a two-phase model from the general effective media theory (GEM). The effective resistance of the cement paste used in the GEM is approximated by the resistance of connected capillary pores as provided by EIS analysis to determine the evolving porosity of cement pastes. The porosity of cement pastes is also experimentally measured by the mercury intrusion porosimetry (MIP) and is then compared with the results obtained from EIS. Meanwhile, two different curing methods were studied their influence on the porosity: (1) the cement pastes were cured in saturated Ca(OH)2 solution and (2) the cement pastes were cured in a humid argon atmosphere before to be transferred in saturated Ca(OH)2 solution.Both MIP and EIS/GEM methods revealed similar porosity results, proving that this innovative methodology is suitable for the in situ determination of the porosity of cementitious matrices in parallel with the analysis of the corrosion reactions.

Synthesis of Aragonite Whiskers by Co-Carbonation of Waste Magnesia Slag and Magnesium Sulfate: Enhancing Microstructure and Mechanical Properties of Portland Cement Paste

This study focused on the synthesis of aragonite whiskers through a synergistic wet carbonation technology utilizing waste magnesia slag (MS) and magnesium sulfate (MgSO4), aiming to improve the microstructure and mechanical properties of ordinary Portland cement (OPC) paste. The influence of MgSO4 concentration on the wet carbonation process, phase composition, and microstructure of MS was investigated. Furthermore, the effect of incorporating carbonated MS (C-MS) on the mechanical properties and microstructure of Portland cement paste was evaluated. Results showed that appropriate MgSO4 concentrations favored aragonite whisker formation. A concentration of 0.075 M MgSO4 yielded 86.6% aragonite with high aspect ratio nanofibers. Incorporating 5% of this C-MS into OPC increased the seven-day compressive strength by 37.5% compared to the control OPC paste. The improvement was attributed to accelerated hydration and reduced porosity by the filling effect and microfiber reinforcement of aragonite whiskers. MS demonstrated good CO2 sequestration capacity during carbonation. This study provides an effective method to synthesize aragonite whiskers from waste MS and use it to enhance cementitious materials while reducing CO2 emissions, which is valuable for the development of a sustainable cement industry.

Chemical Mechanisms Involved in the Coupled Attack of Sulfate and Chloride Ions on Low-Carbon Cementitious Materials: An In-Depth Study

This study aims to analyze the individual and combined chemical attacks of sulfate and chloride ions on cementitious materials and assess the efficiency of some selected additives (fly ash, blast furnace slag, and metakaolin) in countering this combined attack. This research is conducted in the context of construction in marine environments, where reinforced concrete structures are often subject to significant challenges due to early exposure to sulfate and chloride ions. This early exposure results in concrete expansion, cracking, and, ultimately, the corrosion of steel reinforcements. Nevertheless, the interaction between sulfate ions, chloride ions, and the cementitious matrix remains poorly understood. Previous research has drawn conflicting conclusions, with some suggesting that sulfate ions mitigate chloride attacks, while others have come to the opposite conclusion. During this study, experimental investigations were conducted by immersing powders obtained from crushed ordinary Portland cement (CEM I) paste specimens, as well as binary, ternary, and quaternary blends, in sulfate, chloride, and sulfate–chloride solutions over the course of 25 days at an early age. Results from different characterization techniques (thermogravimetric analysis, Fourier Transform Infrared spectroscopy, Raman spectroscopy, etc.) indicate that chloride ions delay the formation of ettringite, while the presence of sulfate ions accelerates the chloride attack by limiting the formation of Friedel’s salt. The Mercury Intrusion Porosimetry test confirmed these results by showing a pronounced increase in specimens’ porosity after exposure to solely sulfate after 25 days, compared to the ones exposed to both sulfate and chloride ions. Furthermore, the incorporation of multiple additives, particularly in ternary and quaternary blends, demonstrates the enhanced durability of the studied samples. This was confirmed by a Fourier Transform Infrared spectroscopy analysis, which indicated a delayed ettringite formation in these mixtures. This delay was further affirmed by the complete depletion of sulfate ions in the sulfate solutions upon contact with powders derived from the 100% CEM I paste.

Investigation of Material Loading on an Evolved Antecedent Hexagonal CSRR-Loaded Electrically Small Antenna.

Recent advances in embedded antenna and sensor technologies for 5G communications have galvanized a response toward the investigation of their electromagnetic performance for urban contexts and civil engineering applications. This article quantitatively investigates the effects of material loading on an evolved antecedent hexagonal complementary split-ring resonator (CSRR)-loaded antenna design through simulation and experimentation. Optimization of the narrowband antenna system was first performed in a simulation environment to achieve resonance at 3.50 GHz, featuring an impedance bandwidth of 1.57% with maximum return loss and theoretical gain values of 20.0 dB and 1.80 dBi, respectively. As a proof-of-concept, a physical prototype is fabricated on a printed circuit board followed by a simulation-based parametric study involving antenna prototypes embedded into Ordinary Portland Cement pastes with varying weight percentages of iron(III) oxide inclusions. Simulation-derived and experimental results are mutually verified, achieving a systemic downward shift in resonant frequency and corresponding variations in impedance matching induced by changes in loading reactance. Finally, an inversion modeling procedure is employed using perturbation theory to extrapolate the relative permittivity of the dielectric loaded materials. Our proposed analysis contributes to optimizing concrete-embedded 5G antenna sensor designs and establishes a foundational framework for estimating unknown dielectric parameters of cementitious composites.

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.

Graphene nanoribbons as a novel nanofiller for enhancing the mechanical and electrical properties of cementitious composites

Several functional fillers have been used to modify the mechanical and electrical properties of cement-based materials. Graphene nanoribbons (GNRs) have attracted considerable attention as the next generation of carbon-based nanomaterials owing to their excellent properties. This paper aims to assess the influence of GNRs with varying incorporation amounts (0.05, 0.10, and 0.15 wt% of cement) on the mechanical properties, hydration behavior, and electrical properties of ordinary Portland cement paste via mechanical strength test, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, and alternating current electrochemical impedance spectroscopy. The enhanced performance of GNRs in cementitious composites was compared with that of carbon nanotubes (CNTs), which are one of the most popular and conventional nano-reinforcing agents for cement-based materials. The results of this study show that, compared to CNTs, GNRs significantly decrease the resistivity of cementitious composites owing to their excellent electrical properties. Furthermore, after the exfoliation of CNTs, GNRs possess a larger specific surface area and exhibit improved dispersibility. Thus, GNRs provide better nucleation and filling effects for cementitious composites to promote the hydration reaction of cement clinkers and modify the microstructure of the cement matrix, resulting in enhanced mechanical properties of the cementitious composites.

Mechanism underlying early hydration kinetics of carbonated recycled concrete fines-ordinary portland cement (CRCF-OPC) paste

Aiming to promote applications of carbonated recycled concrete fines (CRCF) as a low-carbon alternative to ordinary Portland cement (OPC), this study explored the effect of CRCF on the early hydration kinetics of OPC paste. The results show that CRCF is not only a highly active pozzolanic material but also an effective accelerator affecting the early hydration kinetics of OPC paste, thereby leading to an increased early compressive strength and a comparable 28-d compressive strength, even at a replacement ratio of 20%. Although the rheological properties and workability are negatively affected due to the high surface area and fine particle size of CRCF, the amorphous silica and silica-alumina gels and calcite present in CRCF facilitate initial ions dissolution and provide additional active nucleation sites for hydrates. As a result, the microstructure is densified due to the formation of additional C–S–H gels with high Si/Ca and Al/Ca ratios and carboaluminate phases, along with the inert filler effect of unreacted calcite particles. The incorporation of 20% CRCF to replace OPC can achieve a CO2 emissions reduction up to 25%. These indicate that the CRCF has a promising application scenario in transforming wasted concrete into high-value industrial products by CO2 activation.

Constitutive relations of nanoscale hydration products present in engineered cementitious composites from machine learning assisted experimental nanoindentation

In this work, a method to evaluate the stress-strain properties (at nano-scale) of constitutive phases present in the hydration cement matrix is presented. Using an experimental grid nanoindentation using Berkovich indenter, the constituent phases i.e., Low Density Calcium Silicate Hydrate (LD CSH), High Density Calcium Silicate Hydrate (HD CSH) and clinkers are indented upon during different points of Ordinary Portland Cement (OPC) paste hydration. Further, this study is conducted on four other cement pastes: OPC +20% fly ash, OPC +40% fly ash, OPC +0.5% nanosilica and OPC +1% nanosilica. Using experimental grid nanoindentation technique results in a large dataset depending upon the size of the gird. Three different machine learning algorithms including K-means, Gaussian mixture model (GMM) clustering and, support vector machine (SVM) have been implemented. The developed stress-strain evaluation method has allowed to ascertain the constitutive relations as yield stresses of 354 MPa for LD CSH, 393 MPa for HD CSH and 4340 MPa for clinkers, yield strains of 1.8 × 10−2 for LD CSH, 1.1 × 10−2 for HD CSH and 3.7 × 10−2 for clinkers; ultimate stresses of 371 MPa for LD CSH, 424 MPa for HD CSH and 6085 MPa for clinkers, ultimate strains of 2 × 10−2 for LD CSH, 1.4 × 10−2 for HD CSH and 4.4 × 10−2 for clinkers; and strain hardening exponents of 0.85 for LD CSH, 0.72 for HD CSH and 2.1 for clinkers. Elastic modulus, hardness and the stress-strain values obtained from the load vs. displacement curves are used for the clustering analysis and compared with deconvolution results. These properties have been used to test the feasibility of application of machine learning algorithms to classify the grid nanoindentation data. It was found that the machine learning algorithms were indeed capable of clustering the data obtained from experimental grid nanoindentation. This study presents a novel method to evaluate stress-strain properties of the constituent phases present in the cement microstructure and application of machine learning in the field of material characterisation using nanoindentation technique.

Experimental study and mechanism analysis of functional nanocrystalline cellulose to improve the electromagnetic transmission performance of ordinary Portland cement

5G signal transmission can be seriously blocked by cement-based materials, so it is very important to improve the electromagnetic transmission performance (ETP) of cement-based materials. Carboxylated nanocrystalline cellulose (NCC) is used to prepare Ordinary Portland cement paste with high ETP. The water-cement ratio and NCC content of the cement paste are 0.5 and 0–4% respectively. The test results show that the ETP of cement paste increases by 13.9%–90.6%, but the compressive strength of the sample decreases by 7.3%–87.6%. The 2% of NCC content causes the ETP of cement paste increases by 75.6%, while the compressive strength only decreases by 14.6%. The reasons for improvement of ETP are that the electrostatic force between the globule, the polymerization degree and mean chain length of C–S–H, the total volume proportion of phases (calcium hydroxide, ettringite and unhydrated cement) with low dielectric loss and the volume proportion of the no harmful pore for electromagnetic energy loss are increased, the conductivity of cement pore solution and the content of water are decreased.

Effects of sodium carbonate admixture and mix design ratios on the compressive strength of concrete

This study aimed to investigate the impact of sodium carbonate (Na2CO3) admixture on the acceleration and long-term compressive strength of ordinary Portland cement (OPC) concrete at different mix ratios. Concrete cube specimens (150 × 150 × 150mm3 size) were cast at three different mix ratios (1:1.5:3, 1:2:4, and 1:3:6) with sodium carbonate admixture added in increasing dosage of 0.5% from 0 to 2.0% by weight of OPC. Compressive strength tests were conducted on the cast specimens after curing under water for 7, 28, 56 and 90days. Additionally, tests were done to see how sodium carbonate would accelerate setting times of OPC paste. The results of the tests showed that Na2CO3 decreased the initial and final setting times of cement paste from 96 to 67mins and 543 to 387mins respectively. Compressive strength test results for 1:2:4 and 1:3:6 mix ratios showed an increasing trend up to 1.0% Na2CO3 admixture, after which there was a decrease. Meanwhile, 1:1.5:3 mix ratio showed a decrease in strength from 21.87 N/mm2 at 0% to 14.90 N/mm2 at 1.0% Na2CO3 addition, after which the strength increased with Na2CO3 percent addition. These results suggest that sodium carbonate has an accelerating effect on concrete setting time, and may aid its early strength development, but has negative long-term effects on concrete strength with increasing dosage. An optimal percentage of 1% Na2CO3 by weight of OPC is advised for accelerating effects in concrete, based on the results of this study.

Inhibition effect of lithium salts on the corrosion of AA1100 aluminium alloy in ordinary Portland cement pastes

The corrosion inhibition effect of LiNO3 and Li2CO3 has been investigated for protecting aluminium alloy 1100 encapsulated in ordinary Portland cement pastes. A combined approach of electrochemical measurements, scanning electron microscopy and gas chromatography revealed that the corrosion rate of AA1100 is effectively inhibited owing to the formation of a protective corrosion product film in cement pastes with the addition of LiNO3 or Li2CO3. Without any inhibitor, the fast corrosion rate leads to visible cracking in the cement paste matrix. Both the hydration evolution and the curing environment of cement pastes play important roles in the corrosion process.

Examination of sulfate resistance of nano-alumina added ordinary Portland cement paste, focusing on the two different crystallinity of nano-aluminas

This study examined the influence of the crystallinity of added nano-alumina on the sulfate resistance of ordinary Portland cement (OPC) paste. Two crystalline types of nano-aluminas (α-and γ-phase) were incorporated in cement pastes, which were exposed to sulfate solution. In the results, both paste samples having α- and γ-phase aluminas had accelerated compressive strength loss and increased length expansion compared to the sample without alumina addition. In particular, the rapidly decreased dynamic elastic modulus of the nano-alumina added samples postulates the greatly increased internal stress likely by the increased formation of volume expansive reaction products, such as ettringite, which was supported by the XRD and TG results. The greater ettringite formation in the nano-alumina added samples was likely due to reactive AH3 (=Al(OH)3) gel formation as the higher consumption degree of portlandite in the alumina added samples indirectly indicates the active AH3 gel formation, resulting in additional ettringite formation from the reaction of AH3 with Na2SO4 solution. A further degree of sulfate attack was observed in the γ-alumina added sample for the long-term Na2SO4 exposure (180 days) mainly due to the greater degree of gypsum formation inducing more internal expansive stress compared to the α-alumina added sample.

Optimizing a Polycarboxylate Superplasticizer Molecular Structure to Reduce Apparent Viscosity of Cement Paste at Higher Environmental Temperatures

A high environmental temperature can increase the apparent viscosity of high-performance concrete mixtures, causing difficulties in mixing, transporting, pumping, and molding the mixtures. Although polycarboxylate ether–based superplasticizers (PCEs) have been proven effective in reducing the apparent viscosity of cement pastes, little work has focused on how PCEs with various molecular structures affect the apparent viscosity of high-performance concrete mixtures when environmental temperature increases. In this study, a PCE (T54C3.5), which was synthesized by reacting acrylic acid (AA) and isoprenyloxypoly (ethylene glycol) ether macromonomer (TPEG) (mw=2,400 g/mol) with a ratio equal to 3.5∶1, was used as the control group. Variations on the molecular structure of T54C3.5, including different carboxylate-to-macromonomer ratios, backbone lengths, backbone compositions, side-chain lengths, and side-chain compositions, were made to investigate the effectiveness of the various PCEs in changing the apparent viscosity of an ordinary portland cement paste with the water-to-cement ratio of 0.23 at different environmental temperatures. A rotational viscometer was used to measure the apparent viscosity of cement pastes containing different PCEs, and the working mechanisms for the effective PCEs were discussed. Results showed that reducing the backbone length was more effective than the other variations in improving the viscosity-reducing ability of PCEs at all tested temperatures. The PCEs containing ester bonds were able to retain or slightly decrease the viscosity of their cement pastes when the environment temperature increased from 20°C to 40°C. Reducing the backbone length and introducing ester groups are two effective ways of improving the viscosity-reducing ability of PCEs at a high environmental temperature. Using PCEs with these structures can significantly simplify the manufacturing processes of the cement mixtures with a low water-to-cement ratio when the environmental temperature increases from 20°C to 40°C, without any special mixing or casting method.

Effect of using sugar and gypsum as a retarder on concrete properties in Omani weather

This study deals with the retardation of cement setting time and workability in hot weather such as in Sultanate of Oman. Combination of sugar and gypsum was used as retarders. The aim of this study was to investigate the effect of retarders on consistency, setting time of ordinary Portland cement (OPC) paste and compressive strength of concrete cubes after 7 days of curing. OPC paste with a water cement ratio 0.4 to 0.5 was prepared by mixing 500 grams of ordinary Portland cement, a fixed amount of sugar of 0.02% by weight of cement with a combination of different gypsum of 1, 2, 3, 4, and 5% by weight cement and water. Sugar has a strong retarding effect, and this effect, controlled by Gypsum, can shorten the long setting time caused by sugar. The setting time of cement paste was reduced from 5.5 hours to 3 hours with an increase in Gypsum at a fixed amount of sugar. At a constant sugar content, increasing the gypsum content reduced the compressive strength from 31.5 MPa to 30.92 MPa.

Investigation on foam stability of multi-component composite foaming agent

The multi-component composite foaming agent (CFA) with excellent properties was prepared by sodium α-alkenyl sulfonate (AOS), sodium dodecyl sulfate (K12), coconut oil (CO), and rosin liquid (RL), and three foam stabilizers, namely hydroxypropyl methylcellulose ether (HPMC), xanthan gum and sucrose. The foam stability and the foam stability in an alkaline environment and slurry were studied. The results show that the optimal composition of the multi-component CFA is 0.4% AOS, 0.1 % K12, 0.2% RL, 0.3% CO, 0.08% HPMC, 0.6% xanthan gum and 0.6% sucrose. When the CFA is used to prepare foam, the foaming multiple (FM) is 41, and the 1-hour settlement distance (SD) and the 1-hour bleeding ratio (BR) are zero. Moreover, the foam can maintain excellent stability within 2 h. Under an alkaline environment, when the pH is higher than 12.4, the foam stability will be adversely affected. The effective foam ratio (EFR) of foamed concrete increases first and then decreases with the increase of foam content. When foam content is less than 2.8 L/kg, the foam stability in ordinary Portland cement (OPC) paste is better than that of alkali-activated slag (AAS) paste. When the foam content is higher than 2.8 L/kg, the foam stability of the latter is better than the former. When foam content is 2.8 L/kg, the apparent density OPC and AAS system is 698 kg/m3 and 623 kg/m3, respectively. Compared with OPC foamed concrete, AAS foamed concrete presents more small pores, smaller average pore size and better roundness.

Atomistic simulations, meso-scale analyses and experimental validation of thermal properties in ordinary Portland cement and geopolymer pastes

Ordinary Portland Cement (OPC)- and alternative binder-based materials have been widely used in Thermal Energy Storage (TES) applications due to their excellent TES capacities, good mechanical properties and low-cost. In this attempt, this work proposes an upscaling procedure to model the TES properties of two hydrated pastes made of OPC and a Hybrid cement (i.e., an alternative H-Cement binder), the latter employed for a GEOpolymer-based composite (GEO). Firstly, an atomistic approach based on energy minimization and molecular dynamics is employed for modelling the thermal behaviors and heat storage capacities of CSH (calcium silicate hydrate) and NASH (sodium aluminosilicate hydrate) phases, being those the main phases for OPC-based paste and GEO, respectively. Then, an up-scaling optimization procedure and meso-scale FEM homogenization techniques are proposed to link the TES parameters of the atomistic main phases of OPC-based paste and GEO with the homogenized upper meso/macro scale values. To this end, the results of an experimental program on both OPC and GEO pastes have been considered as benchmark to calibrate/validate the numerical tools. Promising simulations at several scales and up-scaling procedures are demonstrated in terms of homogenized temperature-dependent heat capacity and thermal diffusivity, showing a good agreement with the experimental data of the analyzed mixtures.

Strength, shrinkage, heat evolution, and microstructure of high performance concrete containing high proportions of ground bottom ash blended with fly ash

This study examines the use of ground bottom ash incorporating fly ash in high performance concrete. A self-compacting concrete was considered in this study as to maximize the properties of high performance concrete. Bottom ash was processed to a fine consistency by oven-drying, sieving, and grinding. Ordinary Portland cement (OPC), sieved and ground bottom ash (GBA), and fly ash (FA) were used for producing high performance concrete at a W/B ratio of 0.27. Replacement of 50% cement by GBA produced 101.0 MPa concrete at 28 days: 21.6% stronger than OPC concrete. The 50% GBA mixture needed a greater quantity of superplasticizer to satisfy slump flow requirements for self-compacting concrete, but that dosage was reduced with a partial replacement of GBA by FA. Elastic moduli of all blended concretes matched OPC concrete. However, the blended concretes experienced much less autogenous shrinkage. Pastes containing GBA and FA have less portlandite than OPC paste. In addition, replacing OPC by GBA–FA substantially reduced cumulative heat evolution.

Carbonation of Cement Hydrates under Different Relative Humidity Environments Evaluated by Micro-Raman Spectroscopy

In this study, in order to determine the carbonation process relationship between cement hydrates and calcium carbonate polymorph, Raman spectroscopy was applied to measure the carbonation process of ordinary Portland cement and Alite cement paste at different relative humidity. As a result, carbonation of both cement paste was most progressed in the wet environment, while almost no carbonation progress in the dry and 60%RH condition. Calcite and vaterite were the main precipitates in the carbonation of ordinary Portland cement, while calcite was the main precipitate in the carbonation of Alite. The correlation coefficient between cement hydrates and calcium carbonate, and the carbonation rate of cement hydrates were obtained by Raman mapping data.

Synthesis, Stability and Microstructure of a One-Step Mixed Geopolymer Backfill Paste Derived from Diverse Waste Slags

The advent of industrialization has produced an enormous amount of industrial waste slag, which drastically pollutes environmental resources. This study examines the production, stability, and microstructure of a novel backfill geopolymer paste derived from multiple industrial waste slags, including silica-alumina precursors (low-calcium composition) and waste slags (high-calcium composition), as well as two additives. The characteristics of self-hardening were discovered. The effects of low-calcium fly ash, granulated blast furnace slag, red mud, and lime powder on fluidity and compressive strength were then evaluated. To assess the stability, the resistances to drying shrinkage, permeability, and chemical attack by an optimized geopolymer backfill paste were investigated. Furthermore, SEM-EDS, XRD, FTIR, and TG-DSC tests were employed to reveal the microstructures, products, and thermal stability. The results show that the backfill paste hardens well and has no impact on alkalinity dissolution for adjacent soils and water. The optimum sample, P1, had a water-binder ratio of 0.70, resulting in 201 mm fluidity and 2.1 MPa 28-d compressive strength. In terms of drying shrinkage, permeability, and Na2SO4 and NaCl solution attack, sample P1 outperformed the conventional Ordinary Portland cement paste (OPC) for 90 days. The paste P1 containing about 46.0 wt% waste slags meets the fresh and hardened property requirements for goaf backfill, and the chemical binding of P1 is acquired from the mixture of (N,C)-A-S-H, C-S-H, and C-A-S-H gel products. These findings lay the groundwork for the scientific application of a wide range of waste slags in backfill engineering.

Positive impact of polymer impregnated on the enhancement of the physico-mechanical characteristics and thermal resistance of high-volume fly-ash blended cement

To predict the enhanced performance and microstructure design of cement-based composites to achieve sustainability in construction, our study aims to investigate for the first time the positive impact of polymer impregnation on fire resistance and mechanical properties of cement-based composite pastes especially those with high percentages of high-volume fly ash (HVFA) at different water/cement ratios of 0.35, 0.40, and 0.45 and cured up to 90 days. These pastes were dried and impregnated with methyl methacrylate monomer and thermally treated at 70 °C for 3 h using 1% benzoyl peroxide as initiator. The effect of water/cement ratio, curing time, gel space ratio, and bulk density were investigated. Also, XRD, DTG/TGA analysis, and SEM are included. The compressive strength and polymer load were measured after the formation of impregnated- polymer pastes. The results indicated that reducing the w/c ratio leads to the production of hardened cement pastes with dense structures and relatively high compressive strength. For the polymer-impregnated samples, the values of compressive strength were decreased with increasing w/c ratio. The obtained data affirmed that the application of polymer impregnation within a cement matrix can be used to strengthen structures exposed to elevated temperatures. The impregnated cement pastes of ordinary Portland cement (mix OPC1) and blended cement OPC-FA pastes (mix OF1) with water/cement ratios of 0.35 showed higher compressive strength values when thermally treated up to 600 °C after 14 and 28 days of curing.