Accelerate Cement Hydration Research Articles

A closed-loop recycling of wastewater derived from aqueous carbonation of basic oxygen furnace slag in cement paste production

Aqueous carbonation (AC) treatment is a promising method for enhancing the cementitious activity of Ca- and Mg-rich solid wastes, such as basic oxygen furnace slag (BOFS), while also reducing carbon emissions. However, the carbonated filtrate (CF) solution generated during the AC process poses significant environmental challenges and limits its large-scale application. This paper, therefore, explores the feasibility of recycling CF in cement paste production as a strategy for managing AC wastewater. The study examines the impact of CF on the physico-mechanical properties, hydration behavior and microstructure of cement pastes (pure and blended with either 10% as-received or carbonated BOFS), compared to those prepared with tap water (TW) and carbonated water (CW). The results indicate that carbonated solutions (CF and CW) promote the hydration of aluminate phase in cement, with a more pronounced effect observed for CW. The solid suspensions in CF, particularly nesquehonite, restrict the growth space for calcium silicate hydrates (C-S-H) in the paste matrix, resulting in the formation of foil-like Type II C-S-H and lowering compressive strength. However, the additional nucleation sites provided by calcite crystals in carbonated BOFS (C-BOFS) accelerate cement hydration in CF-based pastes and mitigate strength loss by promoting the formation of more fibrillary C-S-H. Furthermore, the addition of a superplasticizer reduces interparticle forces in the C-BOFS-CF paste, further enhancing strength development and achieving a 28-day strength comparable to that of the control sample (OPC-TW paste).

Effects of Polymer-Curing Agent Ratio on Rheological, Mechanical Properties and Chemical Characterization of Epoxy-Modified Cement Composite Grouting Materials.

This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA and analyze the modification mechanism by means of chemical characterization to explore the feasibility of WBER as a high-performance modifier for tunnel construction. The composite grouting is prepared by mixing cement paste with polymer emulsion. A series of experiments was carried out to investigate the effects of WBER and CA, including the slump test, viscosity, rheological curve, setting time, bleeding rate, grain size distribution, zeta potential, compressive and splitting tensile strength, X-ray diffraction(XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), on the composite grout. The results show that WBER improves grout fluidity, which decreases in combination with CA, while also reducing the average particle size of the composite grout for a more rational size distribution. Optimal uniaxial (38.9%) and splitting tensile strength (48.7%) of the grout are achieved with a WBER to CA mass ratio of 2:1. WBER accelerates cement hydration, with the modification centered on the reaction between free Ca2+ and polymer-OH, significantly enhancing the strength, fluidity, and stability of the polymer-modified composite grout compared to traditional cement-based grouting.

Resource utilization of sulfidic copper tailings in calcium aluminate cement: Mechanical property, hydration process and environmental impact

Sulfidic copper tailings (STs) is a byproduct generated from mineral processing activities. To address this environmental burden, calcium aluminate cement (CAC) was used to utilize STs as cementitious materials. The influence of STs on the hydration process, mechanical properties and life-cycle assessment of STs blended CAC were investigated. Results show that the initial setting time of the samples is significantly shortened with the presence of STs. Moreover, the addition of STs greatly accelerates cement hydration and promotes the formation of ettringite, which is caused by the dissolution of sulfidic-rich STs. Hence, the hardened cement paste containing 5 wt.% STs with dense microstructure and high elastic modulus is achieved, which enhances the compressive strength for STs blended CAC. From an environmental point of view, the utilization of STs can save energy and reduce CO2 emissions. Such work may provide new insights into the application of sulfidic copper tailings in low-carbon cementitious materials.

Recent advances in nano-modified concrete: Enhancing durability, strength, and sustainability through nano silica (nS) and nano titanium (nT) incorporation

Concrete, essential to global infrastructure, confronts urgent environmental challenges due to its high carbon footprint and resource-intensive production. In response, researchers are exploring nanoparticles, such as nano-silica (nS) and nano-titanium dioxide (nT), to enhance sustainability and performance. This review examines recent advances in their application. Nano-silica, prized for rapid hydration and enhanced strength, emerges as a promising additive. Studies indicate nS accelerates cement hydration, densifies the matrix, and improves durability and impermeability. Silica-based nano-coatings on glass textile-reinforced composites bolster bond strength and resilience. Similarly, nT offers diverse benefits to concrete. Beyond its traditional applications in photocatalysis, nS has been proven to refine pore structure, increase compressive strength, and enhance resistance to elevated temperatures. Additionally, nT adds to the self-cleaning properties of concrete surfaces, making it a promising additive for sustainable construction practices. Despite these advancements, challenges persist in the effective dispersion of nanoparticles within concrete matrices and ensuring their economic feasibility and regulatory compliance. Addressing these challenges will require interdisciplinary collaboration and innovative approaches to optimize dispersion methods, mitigate health risks, and develop robust regulatory frameworks. Future research directions should focus on developing multifunctional nanomaterials capable of imparting multiple desirable properties to concrete simultaneously, such as self-sensing, self-cleaning, and energy harvesting capabilities. Furthermore, efforts to optimize manufacturing processes and scale up production will be essential to realizing the full potential of nano-modified concrete in addressing the sustainability challenges facing the construction industry.

Study on early hydration and pore structure evolution of cement paste containing graphene oxide

Graphene oxide (GO) significantly enhances cement hydration. This study investigates the effects of GO on the early hydration and pore structure evolution of cement paste by examining its impact on the setting time and mechanical properties of cement-based materials. In situ monitoring of the hydration process and microstructural changes was conducted using low-field nuclear magnetic resonance technology. The findings reveal that GO's nucleation effect accelerates cement hydration, reducing the setting time and increasing both the hydration rate and degree. Moreover, hydration products utilize GO as a template, leading to adjusted morphologies and enhanced interlinking of C–S–H gels. This results in a marked reduction in porosity and a denser microstructure within the cement paste. Consequently, the early mechanical properties of the cement paste are improved, with a significant increase in flexural strength observed at 72 hours. These results suggest that GO, which is cost-effective, size-controllable and suitable for mass production, holds great potential for applications in cement-based materials.

Development of high-dispersion CLDH/carbon dot composites to boost chloride binding of cement

Chloride-induced corrosion of steel reinforcement significantly contributes to the durability deterioration for reinforced concrete (RC) structures. Calcined layered double hydroxide (CLDH) possesses a distinctive structure memory effect to adsorb anions and a nucleation effect to facilitate cement hydration, thereby demonstrating a promising potential for chloride binding enhancement of cementitious materials. However, CLDH suffers from severe agglomeration in cement composites, limiting its performance efficacy. To tackle this problem, novel high-dispersity CLDH/carbon dots (CDs) composites (CC) only at small dosages are applied to greatly improve the chloride binding behavior of cement pastes for the first time. In detail, the specific surface area of CC synthesized by simply stirring CDs and CLDH improves by 166.4 % than that of pure CLDH. Remarkably, cement pastes containing CC display a preferable chloride binding capacity; And the chloride binding substantially increases by 52.41 % when the incorporation of CC (by weight of cement) is 0.8 wt%. More importantly, according to the phase composite and microstructure analyses, the chloride binding enhancement mechanism of CC-containing cement pastes is reasonably ascribed to two effects of CC: providing nucleation sites to accelerate cement hydration and exerting the inherent chloride adsorption capacity. This boosts the formation of C–S–H gels and improves the structure memory effect and anions exchange-induced chloride adsorption, thus significantly strengthening the chloride binding of cement. This work provides a novel approach to improve the dispersity of CLDH, effectively strengthening the chloride binding of cement, thereby conductive to prolonging the service life of RC structures.

Reinforcement effect and mechanism of graphene oxide on mortar with alkali free liquid accelerator

This research mainly investigated the reinforcement effect of graphite oxide (GO) on mortar mixed with alkali free liquid accelerator (AF-LA).The 0.05 % GO and 8.0 % AF-LA were selected as composite additives in cement paste and mortar. Comparative tests showed that the setting time of cement paste was shorter, and the flexural and compressive strength of mortar specimen increased significantly at 1d and 28d. In addition, using XRD combined with TG and SEM analysis, the results showed that GO nanosheets and AF-LA synergistically accelerated cement hydration, especially the hydration of C3S minerals, which resulted in more characteristic portlandite (CH) crystals appearing in the hydration products. Therefore, the above results were the main reasons for the composite of GO and AF-LA to improve the mechanical properties of mortar.

Study on the workability and early mechanical properties of carbon nanotube-coated fly ash modified cement-based grouting materials

Carbon nanotube (CNTs) reinforced cementitious composites have obvious advantages over traditional building materials in strength and impermeable durability. However, the material in question has not been widely employed in grouting engineering due to the limitations posed by dispersion issues. This study introduces a novel method of using amino functional groups to coat carbon nanotubes on the surface of fly ash to improve dispersion. The objective is to produce high-quality industrial-grade slurry and facilitate the transition of carbon nanotubes from small-scale research to large-scale engineering applications. The results show that mixing 14.3 wt% fly ash and 0.023 wt% CNTs in cementitious composites can replace an equivalent proportion of cement. Compared to traditional cement-based grouting material, the modified composites exhibit a 21.6 % increase in fluidity, a 7.9 % increase in the 7-day consolidation strength, and an 11.9 % reduction in the porosity of the slurry consolidation. The CNTs with large specific surface area on the fly ash surface provide sites for cement hydration reaction, accelerate cement hydration, and form dense hydration products. Additionally, the interaction between hydration products and CNTs within the microcracks of the cement matrix forms a 'bridging role' that enhances mechanical properties. The effectiveness of incorporating CNTs in reducing micro-damage during the loading process of slurry consolidation, enhancing integrity, and improving the grouting material's resistance to loading was further proved by acoustic emission, scanning electron microscopy, and fractal analysis of the fracture surface.

Understanding the cavitation effect of power ultrasound in cement paste

While power ultrasound (PUS) has been proven to accelerate cement hydration, it remains unclear whether cavitation occurs during this process. This study aimed to test the cavitation effect of a single bubble in cement paste through a KI oxidation experiment. An ultrasonic pressure field model was established using the linear Helmholtz equation, and the cavitation effect of a single bubble in cement paste was simulated based on the modified Keller–Miksis model. The results indicate that the conventional water-cement ratio (w/c ratio ≤1.0) does not produce transient cavitation but can produce stable cavitation. The efficiency of stable cavitation initially increases and then decreases as the bubble diameter increases. An optimum stable cavitation efficiency is achieved with a 50 μm bubble, but the bubble expansion rate remains consistently less than 40 %. Increasing the acoustic pressure to 5 atm or higher can cause the bubbles in cement paste with a water-to-cement ratio of 1.0 to expand more than tenfold. However, even when the acoustic pressure was further increased to 10 atm, no noticeable bubble expansion was observed in the cement paste with a w/c ratio of 0.30. The high viscosity of cement paste is the primary cause of the high transient cavitation threshold of bubbles.

IMPACT OF ALUMINOSILICATE WASTES ON THE HYDRATION, PHYSICAL AND MECHANICAL PROPERTIES OF CEMENT PASTE

The impact of aluminosilicate wastes (spent fluid catalytic cracking catalyst from oil companies and metakaolin containing waste from the production of expanded glass granules) on the hydration and compressive strength of the cement paste was analysed when a proportion of cement was replaced by one waste material or two waste materials. The article presents results of X-ray diffraction and thermal analysis of hardened cement pastes. It was determined that the spent catalytic cracking catalyst accelerates cement hydration because of its high surface area and pozzolanic activity; and metakaolin containing waste has a retarding effect. X-ray diffraction and thermal analysis showed that the specimens with metakaolin containing waste had the lowest amount of portlandite, and the compressive strength of these specimens was similar to that of the control specimens when a superplasticizer was used. It was found that a mix of aluminosilicate wastes has a different effect on cement hydration and makes it possible to adjust the hydration time of the binder within a certain interval.

IMPACT OF ALUMINOSILICATE WASTES ON THE HYDRATION, PHYSICAL AND MECHANICAL PROPERTIES OF CEMENT PASTE

The impact of aluminosilicate wastes (spent fluid catalytic cracking catalyst from oil companies and metakaolin containing waste from the production of expanded glass granules) on the hydration and compressive strength of the cement paste was analysed when a proportion of cement was replaced by one waste material or two waste materials. The article presents results of X-ray diffraction and thermal analysis of hardened cement pastes. It was determined that the spent catalytic cracking catalyst accelerates cement hydration because of its high surface area and pozzolanic activity; and metakaolin containing waste has a retarding effect. X-ray diffraction and thermal analysis showed that the specimens with metakaolin containing waste had the lowest amount of portlandite, and the compressive strength of these specimens was similar to that of the control specimens when a superplasticizer was used. It was found that a mix of aluminosilicate wastes has a different effect on cement hydration and makes it possible to adjust the hydration time of the binder within a certain interval.

Preparation and hydration of low-carbon UHPC with high fraction of activated tuff and recycled fine powders

Due to the high energy consumption and carbon emission of cement, using active supplementary materials in concrete is widely studied. In this paper, waste tuff micropowder and recycled fine powder (RFP) with maximum replaced ratio of 70 % were investigated by alkali activation in ultra-high performance concrete (UHPC), the mechanical properties and hydration process were studied with different dosages and activators. The results show that the strength activity index of tuff and RFP both enhanced after calcium hydroxide activation. The alkali activator accelerated the hydration speed of tuff and RFP, also leaded to a low heat generated. The compressive strength was reduced with the replaced ratio of tuff and RFP, but the flexural strength was improved once tuff added and cured in appropriate temperature. In the cement-tuff/RFP system, calcium hydroxide accelerates cement hydration and activates part of the tuff and RFP to generate C-(A)-S-H to improve the strength of the mortar. Due to the low degree of tuff activation, less hydration products were formed, leaded to an increase in porosity. The RFP was effectively activated by calcium hydroxide, and the generated C-(A)-S-H and CaCO3 effectively refined the pore structure. The activation of RFP consumed limited mixing water, while the excessive CaCO3 generated by activation will cause the loss of UHPC strength.

Fundamental effects of using power ultrasound to accelerate C3S hydration

Activation of cement hydration accelerates hardening of concrete, enables faster production rates or production at similar frequency but significantly reduced CO2 emissions. The present study sheds light at the reason for accelerated cement hydration when power ultrasound (PUS) is applied during mixing.The investigations analysed the effect of PUS on dissolution of tricalcium silicate (C3S), homogeneous precipitation of C-S-H as well its effect on C3S-hydration. A combination of analytical techniques such as electric conductivity, optical emission spectroscopy, thermogravimetry, conduction reaction calorimetry, scanning electron microscopy and specific surface analysis were applied. It was revealed that PUS has a significant effect on paste hydration, which is induced by heterogenous nucleation of C-S-H and CH immediately after sonication. These hydrates were formed and dispersed by sonication thus acting as in-situ formed crystal seeds which shorten the induction period of C3S hydration.

The dispersion and influence of graphene-oxide-modified polycarboxylate superplasticiser in alkaline cement solution

The aggregation of graphene oxide (GO) in alkaline solutions is a critical factor that limits its potential applications in cement-based materials. In this study, a polycarboxylate superplasticiser (PCE) was employed as a dispersant and a GO–PCE water-reducing agent was synthesised through the method of dropwise addition. This synthesis approach not only preserved the water-reducing capabilities of PCE but also enhanced the dispersibility of GO in alkaline cement solutions. Furthermore, the synthesis method is straightforward. The results showed that that GO–PCE had excellent dispersion in a saturated calcium hydroxide (CH) solution. Furthermore, it was found that the GO–PCE enhanced the workability of cement, accelerated cement hydration, reduced the crystallite size of the CH and increased the compressive strength of the cement mortar.

Ensemble machine learning and Shapley additive explanations for the ability of C-S-H seeds to accelerate cement hydration

Ensemble machine learning and Shapley additive explanations for the ability of C-S-H seeds to accelerate cement hydration

The effect of graphene oxide-fly ash hybridisation on the hydration, microstructure and mechanical characteristics of cement concrete

Carbon-based nanomaterial graphene oxide (GO) can improve cement composites strength and toughness but reduce fluidity. Fly ash is the most common cement substitute for improved fluidity and durability, but early strength growth may be slower. The effects of GO and fly ash on concrete hydration, morphology and mechanical characteristics should be further investigated. GO addition to concrete at 0.025% and 0.05% was investigated by partially replacing cement with fly ash at 10% and 20% by weight. GO addition reduced the concrete fluidity, but the substitution of fly ash increased the fluidity. Moreover, GO compensated for the delayed strength growth of fly ash-based concrete at early-age. The strength properties of GO and fly ash-based concrete at 7 and 28 days are greater than control concrete. Hydration, morphology and elemental composition of concrete were characterised using TGDTA, SEM and EDX. The results demonstrated that GO accelerated cement hydration at early age. Furthermore, GO influenced the total hydration of concrete by expediting secondary hydration of fly ash at later age. Similarly, the morphology of concrete matrix was improved by interweaving hydrated products. This study suggests that using GO and fly ash to produce concrete is an effective process for achieving high performance.

Investigation of physicochemical processes taking place in chemically activated very high volume fly ash mixtures

In order to reduce the negative impact of cement production on the natural environment, and in particular to reduce CO2 emission, new types of binders are sought. It is beneficial to use supplementary cementitious materials, such as fly ash. A very high volume of fly ash and a reduced amount of cement in the binder can, however, result in deterioration of some properties of the final composite. Such systems require activation. The aim of this work was to investigate the effects of different activators: spent aluminosilicate catalyst (very active pozzolanic material), Na2SO4 and Ca(OH)2 on the hydration/activation processes and development of 28-day compressive strength of the blends containing a very high volume of fly ash. Activators were introduced into the system in various combinations: alone or in mixtures. The following research methods were used: calorimetry, thermal analysis, X-ray diffraction and IR spectroscopy. It was shown that each type of activation accelerates cement hydration, improves pozzolanic activity and increases compressive strength compared to the results of non-activated reference sample. However, the activation kinetics and mechanism of interaction are different for different activators. The most promising results were obtained for the combination of three activators: spent aluminosilicate catalyst, Na2SO4 and Ca(OH)2.

Role of the structure of synthetic Al(OH)3 on the properties of sulfoaluminate cement-based materials

A promising approach to accelerate cement hydration has been discovered, wherein superfine particles are utilized to introduce additional nucleation sites for the growth of hydration products. This study investigated the effects of synthetic amorphous aluminum hydroxide (AH3), bayerite, and boehmite on SCGM properties.The results show that amorphous AH3 acted as nucleation sites for the growth of bayerite and ettringite (AFt), bayerite provided nucleation sites for the growth of monosulfate (AFm) and AFt, and boehmite could offer nucleation sites for the growth of AFt. Additionally, synthetic AH3 at pH 12.5 releases AlO2−, and the amount of AlO2− released and the additional generated AFt were the largest for amorphous AH3, followed by bayerite and boehmite. Owing to the synergistic effect of the crystal nuclei and AlO2− released from AH3, synthetic AH3 can promote cement hydration, alter the pore structure of the hardened paste, and improve compressive strength at all ages.

Effect of nano-SiO2 on mechanical properties, fluidity, and microstructure of superfine tailings cemented paste backfill

The application of solid waste filling has emerged as the principal means of achieving cleaner production in mines, due to its substantial environmental benefits. To efficiently utilize superfine tailings, a series of experiments are conducted to investigate the effect of nano-SiO2 (NS) on the performance characteristics of superfine tailings cemented paste backfill (SCPB). The findings indicate that the yield stress, viscosity, and thixotropy of SCPB slurry increase with increasing NS dosage, while the slump flow of SCPB slurry decreases. The uniaxial compressive strength (UCS) of SCPB shows an increasing trend followed by a decreasing trend with rising NS dosage, and reaches its peak at an NS dosage of 1%. NS has a pronounced impact on the early UCS, but only a moderate influence on the mid to late UCS of SCPB. Microanalysis results suggest that NS particles have a strong tendency to agglomerate with each other, and the inability of NS agglomerates to fill the interstitial voids between solid particles curtails the slurry's fluidity. During the early stage of the hydration reaction, NS's volcanic ash effect accelerates cement hydration and exerts a catalytic effect on gypsum, resulting in an increase in products such as C-S-H gels and ettringite crystals. In addition, the C-S-H produced by the use of NS exhibits a decreased Ca/Si ratio and a more robust molecular configuration. This is the fundamental reason why NS has a significant impact on the early UCS. The outcomes of this study can provide crucial direction for the effective utilization of superfine tailings.

The Influence of Curing Temperature on the Mechanical Properties of Cement-Reinforced Sensitive Marine Clay in Column Experiments

The understanding of the mechanical properties of sensitive marine clay subgrade stabilized with cement is vital for the safe, economical, and durable design of road structures. As the curing temperature affects the cement hydration progress, it is necessary to investigate the influence of the temperature on the evolution of the mechanical properties of cement-reinforced marine clay in road construction. A column testing and relevant monitoring program were performed to study the effect of various curing temperatures (2 °C, 22 °C, and 40 °C) on the mechanical properties’ development of cement-reinforced clay within 28 days. After these cement clay samples were cured for a specific time (1, 3, 7, and 28 days), they were subjected to two mechanical tests (i.e., California Bearing Ratio (CBR) test and uniaxial compressive strength (UCS) test). The findings reveal that a higher curing temperature accelerates cement hydration and self-desiccation. Consequently, the UCS and CBR values increase with curing temperature and the strength might vary by more times, especially for early age (≤7 days) samples. The results of this study contribute to a deeper understanding of the influence of temperature on the mechanical properties of the cement-reinforced clay and thus provide practical guidance with regards to road construction in the field.