Properties Of Cement Paste Research Articles

Effect of Activated Siliceous Wastes Incorporated as Mineral Admixtures on the Rheological Properties of Cement Paste: Insights into Their Physicochemical Interactions in Suspension.

Mechanical grinding is a common method used to enhance the pozzolanic activity of tailings, and these activated tailings can be used as supplementary cementitious materials in cement production. However, the addition of activated tailings usually reduces the workability of cement paste, and the mechanism of influence of different minerals in tailings on workability varies. In this study, three kinds of principal silicate minerals in tailings-quartz, feldspar, and mica-were mechanically activated. The influence of these activated minerals on the rheological properties of cement paste were studied in the absence or presence of PCE (polycarboxylate ether) superplasticizers, and the influence mechanism was investigated using rheology, TOC, contact angles, zeta potential, XPS, ICP-OES, and XRD. The results showed that quartz has the highest fluidity, and mica has the lowest. An increase in hydrophilicity decreased the flowability of the blended cement paste. The increase in the metal cation dissolution rate was the main reason for the decrease in the fluidity of PCE-blended cement pastes. The knowledge gained provides a valuable reference for the utilization of activated tailings in cement production.

Mechanism of recalcification and its effects on the microstructure and transport properties of cement paste

Calcium leaching involves the removal of calcium ions from the pore solution and hydration products, leading to a decrease in pH, coarsening of pore structure, and, in severe cases, loss of cohesion, shrinkage, and cracking. Recalcification is a restoration process aiming at repairing degraded C-S-H structures by externally supplying calcium ions. However, our understanding of recalcification mechanism, its potential to reverse calcium leaching, and its effects on deteriorated cementitious matrices remains limited. This study aims at enhancing the understanding of the impact of recalcification on calcium leached cement pastes. Our findings demonstrate that calcium leaching can be partially reversed by immersion in a saturated calcium hydroxide solution. Recalcification functions by introducing calcium ions to the degraded matrix, triggering a reaction with the degraded C-S-H. This process reverses silicate polymerization, increases the Ca/Si ratio in the degraded zone’s, and densifies the pore structure. After only 14 days of recalcification, the degraded portion experienced a 50 % reduction in porosity, an increase in pH. By day 28, recalcification halved the permeability of the treated sample and completely consumed all silica gel. Additionally, our findings reveal that higher temperatures adversely affect the structure of C-S-H, hindering the beneficial structural modifications facilitated by recalcification.

Mechanical property evaluation of 3D multi-phase cement paste microstructures reconstructed using generative adversarial networks

This study proposes an artificial intelligence based framework for reconstructing the 3D multi-phase cement paste microstructure to evaluate its mechanical properties using simulation. The reconstruction of cement paste microstructures is performed using modified generative adversarial networks (GANs) based on microstructural images from micro-CT. For computational efficiency, 2D microstructures are first reconstructed and then extended to 3D microstructures. The reconstructed microstructures exhibit the same microstructural features as the original microstructures when characterized by probability functions. Mechanical properties such as stiffness and tensile strength are evaluated for the original and reconstructed specimens using a phase-field fracture model, and similar behaviors are observed. The results confirm that the reconstructed virtual microstructures can be used to supplement the real microstructures in evaluating the mechanical properties of 3D multi-phase cement paste. This approach thus provides a critical element of a data-driven approach to correlating its microstructure and properties.

Effect of graphene oxide on the properties of ternary limestone clay cement paste

Abstract Given the pressing threat of global warming, it is imperative to promote CO2 emission reduction within the cement industry which is widely recognized as a major contributor to the overall carbon footprint. Limestone clay cement (LCC) emerges as a promising alternative to Portland cement. However, to facilitate the implementation of LCC technology, it is urgent to address the low early-age compressive strength issue. Inspired by the successful implementation of nano-engineered cementitious material, we hereby introduce a novel nanomaterial, graphene oxide (GO), into unconventional LCC paste (cement:clay:limestone = 65%:20%:15%, water/binder ratio: 0.45). Experimental results revealed that the 0.09% GO by weight of the LCC binder was the optimal dosage in this work, which improved the compressive strength of the LCC paste at 7, 14, and 28 days by 25.6, 21.6, and 20.3%, respectively. Advanced characterizations were then conducted, suggesting that the admixed GO not only enabled a higher polymerization degree of binder hydrates (which benefited the development of compressive strengths) but also improved the carbonation resistance of LCC paste. These findings not only offer valuable insights for researchers but also provide practical guidance for engineers in the field. Notably, the admixed GO converted the unstable orthorhombic crystal systemic aragonite to the stable trigonal crystal systemic calcite, which offers insights into the technology of carbon sequestration in concrete.

Study on the electromagnetic transmission properties and mechanical properties of calcium aluminate cement paste by silica fume

Study on the electromagnetic transmission properties and mechanical properties of calcium aluminate cement paste by silica fume

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.

Effect of styrene acrylic latex on the performance of metakaolin blended cement: From hydration to mechanical properties

Effects of styrene acrylic (SA) latex on the hydration and mechanical properties of metakaolin blended cement (MKC) were systematically evaluated through the combined techniques of calorimetry, flow table test, Vicat test, mechanical measurement, QXRD, TGA and SEM. The results show that the presence of metakaolin (MK) greatly changes the interaction of SA polymer with cement grains and then modifies the properties of cement paste and mortar. Specifically, the retardation effect of SA latex on cement hydration can be alleviated through the addition of MK due to its strong adsorption ability to polymer particles, which is beneficial to shorten the setting time of cement paste. The addition of SA latex not only retards the hydration process of cement but also the pozzolanic reaction of MK with portlandite. Contrary to the adverse effect of SA latex on compressive strength, improved strength of hardened MKC mortar was observed with the increased polymer dosage from 4 % to 8 %, which is believed to be caused by the modified microstructure of the matrix through the film formation of SA polymer.

C–S–H-PCE nanoparticles and anionic surfactants as nucleation agent in cement based materials: Focus on the antagonism

The small solid particles and surfactants inclusion have the potential to furnish abundant nucleation sites, yet the concurrent operation mechanisms in cement remain unclear. Thus, calcium-silicate-hydrate-polycarboxylate ether (C–S–H-PCE) nanoparticles and calcium stearate (CaSt2) all were introduced as composites nucleation agents in this work, and then the properties of fresh cement paste, hydration process and microstructure of hardened pastes were especially investigated. Experimental results demonstrated that C–S–H-PCE and CaSt2 enhanced cement hydration by utilizing their ability to provide nucleation sites, but they were less compatible. Therefore, the combination showed the antagonistic effects: a decrease in fluidity and compressive strength. The decrease in fluidity was mainly attributed to the lowered particle dispersion. The decrease in compressive strength was associated with a lower overall density and increased cumulative porosity of the C–S–H gels. This work establish the theoretical foundation for selecting components of green composite nucleation agents.

Enhancement of the tensile properties of cement mortar composites with nanoadditives produced by chemical vapor deposition

While graphene effectively enhances the performance of cement-based materials, its current production methods are characterized by environmental unfriendliness and high energy consumption. To investigate a large-scale and eco-friendly graphene preparation approach, Carbon Nano Sheets (CNS) were synthesized via chemical vapor deposition (CVD). The influence of CNS content on the tensile strength of cement mortar was assessed through the Brazilian splitting test. Concurrently, the mechanism of CNS was examined using acoustic emission monitoring and scanning electron microscope. The experimental results revealed that methane can be effectively decomposed into high-quality CNS at 1080 ℃ when using fly ash, silica fume, and sand as substrates. The Brazilian splitting test revealed that CNS effectively enhances the tensile strength of cement mortar, with improvements ranging from 9 % to 58.7 %. Acoustic emission results indicated that the inclusion of CNS reduces the occurrence of micro-fractures during the failure of cement mortar specimens. Furthermore, nano-mechanical testing and microstructural characterization demonstrate that CNS can reduce micro-cracks and pores in the interface transition zone and hydration products, playing a role in dense hydration products. Furthermore, it can decrease the width of the interface transition zone and enhance the micro-mechanical properties of cement pastes. This study offers a novel approach for the eco-friendly production of cement nano additives.

Investigating the Impact of Superabsorbent Polymer Sizes on Absorption and Cement Paste Rheology.

This study aims to understand the water retention capabilities of Superabsorbent Polymers (SAPs) in different alkaline environments for internal curing and to assess their impact on the rheological properties of cement paste. Therefore, the focus of this paper is on the absorption capacities of two different sizes of polyacrylic-based Superabsorbent Polymers : SAP A, with an average size of 28 µm, and SAP B, with an average size of 80 µm, in various solutions, such as pH 7, pH 11, pH 13, and cement filtrate solution (pH 13.73). Additionally, the study investigates the rheological properties of SAP-modified cement pastes, considering three different water-to-cement (w/c) ratios (0.4, 0.5, and 0.6) and four different dosages of SAPs (0.2%, 0.3%, 0.4%, and 0.5% by weight of cement). The results showed that the absorption capacity of SAP A was higher in all solutions compared to SAP B. However, both SAPs exhibited lower absorption capacity and early desorption in the cement filtrate solution. In contrast to the absorption results in pH 13 and cement filtrate solutions, the rheological properties, including plastic viscosity and yield stress, of the cement paste with a w/c ratio of 0.4 and 0.5, as well as both dry and wet (presoaked) SAPs, were higher than those of the cement paste without SAP, indicating continuous absorption by SAP. The viscosity and yield stress increased over time with increasing SAP dosage. However, in the mixes with a w/c ratio of 0.6, the values of plastic viscosity and yield stress were initially lower for the mixes with dry SAPs compared to the reference mix. Additionally, cement pastes containing wet SAP showed higher viscosity and yield stress compared to the pastes containing dry SAP.

The influence of graphene oxide on the hydration and mechanical properties of cement-based materials with low water-binder ratio

Graphene oxide (GO) has been used as a functional material in cement-based materials. Most of current research suggests that GO effectively enhance the mechanical properties of cement paste with high water-to-binder (w/b) ratios (0.30–0.50). However, due to the high cost of GO, its use in ordinary concrete materials with high w/b ratios is limited. It has shown promising potential for reinforcement in ultra-high performance cement-based materials with low w/b ratios, such as UHPC. Nevertheless, existing studies have paid limited attention to the effects of GO in cement-based materials with low w/b ratio. This study selected cement-based materials with a w/b ratio of 0.17 as a representative example to investigate the changes in the mechanical properties of hardened cement paste after the addition of GO under different curing conditions. Additionally, by combining the results of microstructural analysis of hydration products, the study explored the mechanism by which GO affects the mechanical properties of cement-based materials with low w/b ratios. The research findings indicate that though an appropriate dosage of GO enhances the compressive strength of cement-based materials with low w/b ratios, it significantly reduces their flexural strength. In addition, GO accelerates the dissolution process of Ca2+ in the early stages, enhancing the degree of cement hydration and increasing the thickness of inner hydration products (IP). This action leads to an increase in the calcium-to-silicate (Ca/Si) ratio and a weakening of the microstructure in outer hydration products (OP). Resultantly, these changes lead to the refinement of small pores and the coarsening of large pores within the hardened cement-based material, collectively manifesting as an improvement in compressive strength and a reduction in flexural strength of the cement paste.

Evaluation of electrical resistivity of cement-based materials using time domain reflectometry

Time domain reflectometry (TDR) is a widely used electromagnetic wave–based technique for evaluating the volumetric water content of soils, although its use for moisture measurement in cement-based materials is limited. This paper presents a comprehensive analysis of the electrical properties of cement pastes and cement paste–slime mixtures using TDR. Both TDR and electrical resistivity probes are used to estimate the electrical resistivities of various cement-based materials over their curing period. The study reveals that these properties are significantly influenced by curing time, water–cement ratio, and water–solid ratio. The experimental results demonstrate a consistent increase in electrical resistivity with curing time, underscoring the significant role of hydration-induced water evaporation and microstructural changes. Furthermore, the interpretation of characteristic voltages on the TDR waveform significantly influences resistivity estimates. Thus, this study highlights the potential of TDR in accurately evaluating the electrical resistivity of cement-based materials.

Development of a universal atomistic cement model incorporating nanomaterials: From laboratory investigation to molecular simulation

Hydrated cement is considered one of the most complex binder systems. The development of models that suitably represent hydrated cement is still far from established due to the complexity of the hydration process, as well as the multiscale phase and different morphological properties. Therefore, this study attempts to develop a hydrated cement model using molecular-level simulation and laboratory testing. This model aimed to predict the mechanical properties of cement paste between 0.25 and 0.65 w/c ratios. In this regard, five cement paste mixtures with various w/c ratios were prepared and tested to evaluate their mechanical properties and micro-structures. Then, a novel modeling methodology using molecular dynamics (MD) simulation was carried out to develop an ingredient-based atomistic cement model. In this regard, the Dreiding force field (DFF) was used in all the simulation processes, starting from the cement clinker phases to the hydrated cement. The experimental results of cement paste mixtures revealed some useful data that was supportive of the simulations. Radial distribution function (RDF) and fractional free volume (FFV) were utilized to investigate the local atomic structure of the cement paste models. The calcium-silicate-hydrated (C–S–H) of the developed model was characterized through RDF and benchmarked to a well-known mineral analog, namely tobermorite. The developed model was computationally tested under different w/c ratios, and reliable results in terms of micro-structural matrix as well as mechanical properties were obtained. Then, the cement models incorporating different ratios of nano-silica were developed, and a good estimation of the mechanical properties was obtained. Because of the universal nature of the reported model in this research, it could be utilized to further predict the mechanical behavior and durability performance of the cement paste.

Influence of Starch Admixtures and Silver Colloids Stabilised with Starch Hydrolysates on the Course of Electrochemical Potential Difference of Reinforcing Steel in High-chloride Environment

The purpose of the conducted study was to verify whether the use of concrete admixtures with modified starches and starches modified with stabilised silver colloids affects the course of electrochemical potential difference, and hence corrosion, of reinforcing steel in a chloride environment. In the tests, cross-linked starches and products of acid hydrolysis of starch (dextrins) were used as admixtures. The 1-molar aqueous solution of sodium chloride was used as an aggressive environment. The tests consisted of measuring the potential difference generated in the reinforcement corrosion cell on the surface for a period of 60 days and then assessing the risk of corrosion. The effect of the addition of starch derivatives on the properties of cement paste was investigated through a one-way ANOVA analysis of variance followed by post hoc tests. The test results showed that the use of concrete admixtures with cross-linked starches positively affects the passivation of the steel. The likelihood of reinforcing steel corrosion when using distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate admixtures is less than 5%. The results obtained showed an improved effect on the passivation of reinforcing steel in cement composites. Additionally, concrete samples may have microbicidal properties.

Film-Forming Property of Cement Paste with Red Mud as a Supplementary Cementitious Material

Film-Forming Property of Cement Paste with Red Mud as a Supplementary Cementitious Material

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.

Circular Economy Approach: Recycling Toner Waste in Cement-Based Construction Materials

Based on a waste generated survey by companies in the area of the city of Bahia Blanca (Argentina), the possibility of incorporating part of them in a Portland cement matrix was examined. Among the waste is toner (TW), which is obtained from cartridges used in photocopiers, laser printers, and faxes. This paper aims to analyze the physical and mechanical properties of cement pastes and mortars using toner as a Portland cement replacement compared to a reference sample without toner. The mixes were made with 2.5, 5, 10, and 15 wt.% replacement of cement by toner, and it was measured the flow, normal consistency, setting time, calorimetry, and Frattini test in pastes and mechanical strengths in mortars employing standardized tests. Also, an analysis of the leachate in the curing water was carried out after 56 days to look for contaminating materials. The replacement of up to 5% cement with toner did not produce substantial alterations in the final setting time or mechanical properties. No heavy metals were found in the leachate, so TW can be immobilized in a cementitious matrix as it does not cause leaching above the established limits. Therefore, TW from a local industry can be used in construction materials and could contribute to a reduction of up to 14% of CO2 emissions with a cement replacement of 15% in cement-based materials.

Peridynamic simulation of micro-internal damage and macro-mechanical properties of cement paste under freeze-thaw cycles

Concrete is a multi-phase, multi-component, heterogeneous composite material and a typical porous medium with a complex microstructure. Under freeze-thaw cycles (FTCs), pressures from the freezing and migration of water within the pores of the concrete cause freeze-thaw damage, which is influenced by its microstructure. To effectively simulate and understand the freeze-thaw damage mechanism, it is crucial to use a geometric structure that reflects the actual pore distribution. This study employs the μic model to create a geometric structure of hardened cement paste, capturing the spatial distribution of pores. The study utilizes the peridynamics (PD) method based on ice formation and crystallization thermodynamics to investigate the freeze-thaw damage evolution and the deterioration of mechanical properties in cement paste under FTCs. The simulations revealed the entire freeze-thaw damage process of cement paste, including internal crack initiation and propagation, as well as surface freeze-thaw spalling. The freeze-thaw damage of cement paste intensifies with increasing FTCs, and the extension of cracks diminishes the interconnection among the skeletons constituting the cement paste microstructure, leading to decreased tensile strength and elastic modulus. Additionally, the stress-strain evolution behavior of freeze-thaw cement paste under uniaxial tensile loads was obtained. The tensile strength and elastic modulus of cement paste decrease with increasing FTCs, and the higher the water-cement (w/c) ratio, the greater the reduction in strength and modulus.

Impact of aragonite coral powder on hydration, strength, and rheology of cement paste

Understanding the intricate bonding mechanism between coral reef surfaces and C–S–H is crucial for advancing large-scale engineering applications. This study conducts a comprehensive analysis of the impact of coral powder (CP) on cement paste. Initially, zeta potential experiments were performed to probe ion adsorption from the cement pore solution at the CP interface. We propose a novel model to quantify the adsorption of Ca2+ by CP. Subsequently, the study delves into the morphological properties of C–S–H nucleation and growth at this interface and formulates an equation elucidating the CP and Ca2+ adsorption relationship. Then, the crack extension behavior of cementitious materials was scrutinized. Finally, an examination of CP effects on the rheological properties of fresh cement pastes is presented. The findings indicate that CP particles exhibit a notably weaker adsorption affinity with Ca2+ compared to their interaction with SO42−. Compared to limestone (LP), CP exhibited a 32.1 % reduction in Ca2+ adsorption in Ca(OH)2 solutions, 44.2 % reduction in Ca(OH)2 + 10 mmol/L K2SO4, and 40.6 % reduction in Ca(OH)2 + 50 mmol/L K2SO4 solutions. Higher zeta potential values correspond to stronger Ca2+ adsorption and broader surface coverage of Ca2+. The inferior surface characteristics of CP hinder C–S–H nucleation and growth, leading to a low CH orientation index in cement paste containing CP. These pastes exhibit cracks more frequently between CP and hydration products. An attractive force is observed between CP and cement particles, decreasing cement paste flowability.

Mechanical properties of cement pastes containing plasma-treated silicon-based materials

The study delves into the impact of waste silicon-based materials on the mechanical characteristics of the resulting cement pastes. The investigation uses Portland cement CEM I 42.5R in conjunction with silicon-based waste materials sourced from the packaging industry, specifically from Recifa, a.s. Variations between the sample groups arise from differences in the concentration of silicon-based materials and the method of surface treatment. The inquiry seeks to assess the effects of two distinct levels of Si-based material incorporation, namely 10 wt. % and 20 wt. %, along with plasma treatment involving two different gases: oxygen (O2) and hydrogen (H2). The mechanical attributes under scrutiny encompass compressive and flexural strengths. The evaluation of mechanical properties is carried out on samples aged 28 days, with dimensions measuring 20 × 20 × 100 mm.