Search Results (130)

Polycarboxylate superplasticizer (PCE) is an important part of improving the overall performance of concrete. However, its synthetic raw materials are overly dependent on petrochemical products, and it also causes problems such as environmental pollution. With the development of the building material industry, the demand for petrochemical resources required for synthetic water-reducing agents will increase rapidly. Therefore, there is an urgent need to transition the synthetic raw materials of PCE from petrochemicals to biomass materials to reduce the consumption of nonrenewable resources as well as the burden on the environment. Biomass materials are inexpensive, readily available and renewable. Utilizing biomass resources to develop good-performing water-reducing agents can reduce the consumption of fossil resources. This is conducive to carbon emission reduction in the concrete material industry. In addition, it promotes the high-value utilization of biomass resources. Therefore, in this study, a biomass polyether monomer, acryloyl hydroxyethyl cellulose (AHEC), was synthesized from cellulose via the reaction route of ethylene oxide (EO) etherification and acrylic acid (AA) esterification. Biomass polycarboxylate superplasticizers (PCE-Cs) were synthesized through free radical polymerization by substituting AHEC for a portion of the frequently utilized polyether monomer isopentenyl polyoxyethylene ether (TPEG). This study primarily focused on the properties of PCE-Cs in relation to cement. The findings of this study indicated that the synthesized PCE-C5 at a dosing of 0.4% (expressed as mass fraction of cement) when the AHEC substitution ratio was 5% achieved good water reduction properties and significant delays. With the same fluidity, PCE-C5 could enhance the mechanical strength of cement mortar by 30% to 40%. This study utilized green and low-carbon biomass resources to develop synthetic raw materials for water-reducing agents, which exhibited effective water-reducing performance and enhanced the utilization rate of biomass resources, demonstrating significant application value. Full article

Additive manufacturing (AM) has brought significant breakthroughs to the construction sector, such as the ability to fabricate complex geometries, enhance efficiency, and reduce both material usage and construction waste. However, several challenges must still be addressed to fully transition from conventional construction practices to innovative and sustainable green alternatives. This study investigates the use of non-cementitious traditional mixtures for green construction applications through 3D printing using Liquid Deposition Modeling (LDM) technology. To explore the development of mixtures with enhanced physical and mechanical properties, natural pine and cypress wood shavings were added in varying proportions (1%, 3%, and 5%) as sustainable additives. The aim of this study is twofold: first, to demonstrate the printability of these eco-friendly mortars that can be used for conservation purposes and overcome the challenges of incorporating bio-products in 3D printing; and second, to develop sustainable composites that align with the objectives of the European Green Deal, offering low-emission construction solutions. The proposed mortars use hydrated lime and natural pozzolan as binders, river sand as an aggregate, and a polycarboxylate superplasticizer. While most studies with bio-products focus on traditional methods, this research provides proof of concept for their use in 3D printing. The study results indicate that, at low percentages, both additives had minimal effect on the physical and mechanical properties of the tested mortars, whereas higher percentages led to progressively more significant deterioration. Additionally, compared to molded specimens, the 3D-printed mortars exhibited slightly reduced mechanical strength and increased porosity, attributable to insufficient compaction during the printing process. Full article

This study focuses on the development of high-performance composite cementitious materials for offshore engineering applications, addressing the critical challenges of durability, environmental degradation, and carbon emissions. By incorporating polycarboxylate superplasticizers (PCE) and combining fly ash (FA), ground granulated blast furnace slag (GGBS), and silica fume (SF) in various proportions, composite mortars were designed and evaluated. A series of laboratory tests were conducted to assess workability, mechanical properties, volume stability, and durability under simulated marine conditions. The results demonstrate that the optimized composite exhibits superior performance in terms of strength development, shrinkage control, and resistance to chloride penetration and freeze–thaw cycles. Microstructural analysis further reveals that the enhanced performance is attributed to the formation of additional calcium silicate hydrate (C–S–H) gel and a denser internal matrix resulting from secondary hydration. These findings suggest that the proposed material holds significant potential for enhancing the long-term durability and sustainability of marine infrastructure. Full article

The utilization of red mud by blending it into cement paste is still facing poor workability issues due to the finer particle size and higher water absorption of red mud, which can be solved by the addition of polycarboxylate superplasticizer (PCE) to effectively maintain the working performance. However, the specific mechanisms by which different topologies of PCEs, in terms of water-reducing (WR)- and slump-retaining (SR)-type PCEs, influence red mud blended cement paste require further clarification. This research investigates the effect of WR-PCE and SR-PCE on the rheological properties, mechanical properties, and microscopic morphology of red mud blended cement paste under different red mud contents. The results demonstrated that at saturated dosages of 0.5% WR-PCE and 0.75% SR-PCE, both types of PCEs improved paste fluidity and reduced plastic viscosity and shear stress. Moreover, the time-dependent fluidity loss rate of the SR-PCE-incorporated paste was lower to that of the WR-PCE-incorporated paste at 30 and 60 min. With 0% and 25% red mud contents, the compressive strengths at 1, 3, 7, and 28 days were higher for WR-PCE than for SR-PCE due to the enhanced hydration of C₂S and C₃S. Furthermore, hydration products in the WR-PCE-incorporated paste were more uniformly distributed compared to the SR-PCE-incorporated paste. However, a 50% red mud content negatively impacted paste strength, likely due to the high alkalinity destabilizing the PCE. This study aims to elucidate the mechanistic relationship between PCE topology and the improved performance of red mud blended cement paste. Full article

This study aimed to improve the mechanical properties and water resistance of calcined gypsum from phosphogypsum (CGP) by incorporating organic additives and inorganic admixtures. The effects of the dosage of these additives—including kaolin, nano-SiO₂, polycarboxylic acid superplasticizer, and sodium methyl silicate—on the properties (flexural strength, compressive strength, water absorption, and softening coefficient) of CGP composites (CGPCs) were investigated. A high water resistance of the CGPCs was achieved using nano-SiO₂ and sodium methyl silicate modification, superplasticizer addition, and the partial replacement of gypsum with mineral admixtures. The results showed that the flexural and compressive strength of the composites hit 4.61 MPa and 19.54 MPa, respectively, while the softening coefficient was 0.70 and the water absorption rate was 19.85%. Microstructural investigation confirmed that the combination of nano-SiO₂ and kaolin led to the formation of calcium silicate hydrate. Additionally, the superplasticizer played a crucial role in reducing the water-to-cement ratio, while unhydrated mineral particles had a filling effect, thereby enhancing the density of the hardened paste. The sodium methyl silicate formed a hydrophobic film on the surface of the hardened paste, increasing the contact angle to 109.01° and improving the water resistance of the CGPCs. Full article

In contemporary construction practices, polycarboxylate superplasticizers (PCEs) have gained extensive utilization in concrete formulation owing to their exceptional dispersive properties and superior water reduction capabilities. Nevertheless, these admixtures demonstrate pronounced susceptibility to clay contamination, a critical limitation that substantially constrains their practical implementation. To mitigate this detrimental effect, multiple technical strategies have been developed to suppress clay sensitivity, with predominant approaches focusing on molecular structure optimization and incorporation of supplementary admixtures. This review systematically investigates the competitive adsorption mechanisms operating at the cement–clay interface. Through rigorous analysis of molecular architecture characteristics and synergistic admixture combinations, we comprehensively review current methodologies for enhancing the clay resistance of PCE-based systems. Furthermore, this paper proposes prospective directions for synthesizing clay-tolerant PCE derivatives, emphasizing molecular design principles and advanced formulation protocols that may inform future research trajectories in construction materials science. Full article

This study aims to investigate the effects and mechanisms of polycarboxylate superplasticizers (PCEs) on alkali-activated circulating fluidized bed fly ash (CFBFA) materials. Two PCEs—APEG-500 and APEG-2400—were synthesized using allyl polyethylene glycol ethers (APEG) with molecular weights of 500 and 2400, respectively. Their water-reducing performance and impact on the compressive strength of alkali-activated CFBFA materials were evaluated. The results show that both PCEs exhibited significant water reduction (up to 28% for APEG-2400) in pure CFBFA paste systems, but their efficacy was largely diminished in alkali-activated systems. Compared to the control group without PCEs, APEG-500 improved compressive strength by 20.37% at 1 day and 33.00% at 28 days, while APEG-2400 exhibited lower early strength but achieved a 10.31% strength increase at 28 days. Mechanistic analyses via XRD and FTIR analyses indicated that there was no significant alteration in reaction products, suggesting that the shorter side chains of APEG-500 facilitated particle adsorption and accelerated early hydration. Mercury intrusion porosimetry revealed that PCEs refined the pore structure by increasing harmless pores and reducing harmful ones, with APEG-2400 showing an 11.11% higher proportion of harmful pores compared to APEG-500. SEM observations supported these findings. This study clarifies the relationship between PCE molecular weight and CFBFA material properties, providing a basis for optimizing CFBFA-based cementitious materials. Full article

In order to improve early-age strength, steam curing is mostly used for railway prefabricated components, which consumes a lot of energy and affects the durability of concrete. Synthetic calcium silicate hydrate (C-S-H) has an excellent early-age strength effect, which can improve the early-age strength of concrete and help to reduce the energy consumption of steam curing, but C-S-H will increase the shrinkage of concrete and affect the durability of concrete. In this work, C-S-H/SRPCA was synthesized using a shrinkage-reducing polycarboxylate superplasticizer (SRPCA) in order to increase the early-age strength and decrease the shrinkage of concrete. The effects of 0.5%, 4.0%, and 8.0% C-S-H/SRPCA on the shrinkage and strength of concrete were studied. Meanwhile, the internal mechanism was also explored through cement hydration, the physical aggregation morphology of hydration products, pore structure and classification, and the chemical properties of pore solution. The results suggest that C-S-H/SRPCA can shorten the setting time and accelerate cement hydration. Specifically, when the dosage of C-S-H/SRPCA is 4.0%, the initial setting time of concrete is shortened by 2.5 h and the final setting time is shortened by 6.2 h compared with the control group. As a result, the 1-day compressive strength is effectively increased by 29.5%, and the plastic shrinkage is reduced. In the stage of plastic shrinkage, the plastic shrinkage time of the concrete with 4.0% C-S-H/SRPCA is 4.1 h, which is 6.1 h shorter than that of the control group. In addition, C-S-H/SRPCA decreases the porosity. When the dosage is 4.0%, the porosity of the hardened cement paste at 28 days is reduced by 15% compared with the control group. It lessens the content of the capillary pores at 10–50 nm. At 24 h, the content of 10–50 nm capillary pores in the paste with 4.0% C-S-H/SRPCA is 40% lower than that of the control group. It also reduces the surface tension of the pore solution. The surface tension of the simulated pore solution with 4.0% C-S-H/SRPCA is 34 mN/m, which is 53% of that of the control group, and it inhibits the volatilization of the pore solution. At 28 days, the evaporation rate of the pore solution in the paste with 4.0% C-S-H/SRPCA is 40% lower than that of the control group. Thus, the drying shrinkage of concrete is inhibited. Given the above, at the optimum content of 4.0%, C-S-H/SRPCA improves the 1-day compressive strength of concrete by 29.5%, reduces the 28-day total shrinkage by 21.7%, and restrains the development of microcracks. Full article

The environmental hazards caused by the massive generation and improper disposal of industrial solid wastes (e.g., high calcium desulphurization ash, HCDA) and the growing safety risks posed by the increasing number of underground mine goafs generated by mining activities have become serious environmental and geotechnical challenges. To address the dual issues, this study develops a novel desulfurization ash–slag-based paste backfill (DSPB) material using HCDA and granulated blast furnace slag (GBFS) as primary constituents. The effects of cementitious material ratios, polycarboxylate superplasticizer (PCE), and sodium silicate (SS) on rheological properties of DSPB were investigated through a shear rheology experiment and fitting rheological model to assess the flow conditions in pipeline transportation. In addition, the mechanism was investigated through microanalysis. The results showed that with the decrease in desulfurization ash-to-slag ratio, the initial yield stress and plastic viscosity decreased by up to 88% and 34.9%, respectively; PCE via “card house” structural effects made the rheological parameters increase and then decrease, and a dosage of more than 1.2% significantly improved the rheological properties; and SS initially reduced the rheological parameters, but excessive doping (greater than 1.0%) led to an increase. These findings establish the relationship between DSPB composition and rheological properties, provide a practical solution for waste resource utilization and surface stabilization, and provide a scientific basis for the microstructure–rheology relationship of cementitious systems. Full article

The article investigates the characteristics of the phase composition and structure of supersulfated cement (SSC) during hardening using X-ray, electron microscopy, and ultrasonic analysis methods. The influence of different types of activators, hardening accelerators, and superplasticizers on the type and morphology of the newly formed phases during SSC hardening was studied. The effect of a polycarboxylate-type superplasticizer and calcium chloride on the standard consistency and setting times of SSC was experimentally determined. It was established that the introduction of the superplasticizer reduces the standard consistency by 10–16%. Experimental data showed higher effectiveness of phosphogypsum as a sulfate activator compared to gypsum stone. The strength increase of SSC at 7 days reached up to 35%, and at 28 days, up to 15%. Based on the kinetics of ultrasonic wave propagation during SSC hardening, the main stages of structure formation and the influence of cement composition on these stages were determined. The experimental results demonstrate the effect of SSC composition on its standard consistency, setting time, and mechanical properties. The impact of the type of activator and admixtures on the change in SSC strength during storage was investigated. It was found that the addition of a polycarboxylate-type superplasticizer significantly reduces the strength loss of SSC during long-term storage. Using mathematical modeling, experimentally obtained statistical models of strength were developed, which allow for the quantitative evaluation of individual and combined effects, as well as the determination of optimal SSC compositions. Full article

Polycarboxylate superplasticizers (PCEs) are the most important polymer admixtures in cement and concrete. Developing novel, green, and efficient synthesis methods is essential for lowering energy consumption. Here, a mechanochemical internal mixing polymerization was used to synthesize high-concentration PCEs (INPCEs) for the first time. The optimum reaction temperature, reaction rotating speed, and reaction time were determined using the orthogonal method. The optimum acid–ether ratio (i.e., the molar ratio of acrylic acid (AA) to isopentenyl polyoxyethylene ether (TPEG)) and concentrations of ammonium persulfate (APS) and sodium methacrylate sulfonate (MAS) were also determined. Finally, the molecular structures of the INPCEs were characterized using Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC), and their performance and energy consumption were compared with PCE synthesized via an aqueous solution polymerization (TPCE). The results showed that the optimum reaction temperature, rotating speed, and time were 60 °C, 70 R/min, and 60 min, respectively. In addition, the acid–ether ratio, the concentrations of MAS and APS, and the polymerization method affected the molecular weight and PDI of INPCEs but did not alter the functional groups. At an AA:TPEG:MAS molar of 3.0:1:0.12 and an APS concentration of 1 wt% (relative to TPEG), the initial fluidity of cement paste with INPCE was 312.5 mm at an INPCE dosage of 0.20 wt% and a water–cement ratio of 0.35. Further, the concentrations of the INPCEs were >99.00 wt%, which is much higher than the TPCE concentration of 39.73 wt%, and the dispersion and dispersion retention of INPCE was almost as good as that of TPCE while requiring much less energy for synthesis. These findings can contribute to the reduction in energy consumption in the concrete industry. Full article

It is difficult to obtain efficient flowability of reactive powder concrete (RPC) mix due to a low water/binder ratio. The improvement of material flowability could be achieved by using the latest generation polycarboxylate superplasticizers (SPs), as well as by changing the mixing procedure. This paper presents two different superplasticizers’ effect on a fresh mix and hardened reactive powder concrete properties. Results of systematic experimental studies (including physicochemical and spectroscopic tests) and molecular modelling suggest that superplasticizer chemical structure plays a key role in shaping the properties of the concrete mix. It has been demonstrated that SP containing more carboxylate salt groups -COO⁻ Me⁺ improves fluidity of the RPC mix and causes its better deaeration. In contrast, hardened concrete exhibits lower porosity and consequently greater strength. On the other hand, a change in ingredients mixing from a three-stage to a four-stage procedure increased the mix flowability and the RPC strength. The chemical structure of SP and the mixing procedure had no significant impact on cement hydration progress. Our results could be useful both from the point of view of the basic science of materials and the applied field of planning of cement composites in construction. Full article

The incorporation of circulating fluidized bed (CFB) fly ash into self-leveling cement-based (SLC) paste production presents significant environmental advantages. However, its addition deteriorates the fresh properties of the paste, posing challenges for practical implementation. This research examined the fresh properties of SLC paste blended with CFB fly ash, emphasizing fluidity, rheological characteristics, and bleeding rate. To enhance flowability, polycarboxylate superplasticizer (PCE) was incorporated, with particular emphasis on its interaction with CFB fly ash. The findings reveal that adding CFB fly ash to cement-based paste significantly decreased fluidity while increasing yield stress and plastic viscosity. Incorporating 20 wt.% CFB fly ash reduced paste fluidity by 51.4%, while plastic viscosity and yield stress increased by factors of 2.3 and 73, respectively. While PCE enhanced the fluidity of the blended paste, its water-reducing efficiency diminished, and the bleeding rate of the paste increased with higher CFB fly ash dosage. The water-reducing capability of PCE in the CFB fly ash-blended cement paste with 20 wt.% CFB fly ash decreased by 40.0%, and the bleeding rate of the paste increased from 0.6% to 6.7%. This effect was primarily attributed to the poor compatibility between PCE and CFB fly ash. The decline in PCE efficiency with higher CFB fly ash content, along with its lower adsorption capacity on CFB fly ash compared to cement particles, further confirmed this incompatibility. Full article

Graphene oxide (GO) significantly enhances cement hydration at the nanoscale; however, its tendency to complex and agglomerate with Ca²⁺ in cement paste remains an unresolved issue. To improve the dispersibility and enhance the reinforcing effect of GO in cement paste, polycarboxylate (PC) superplasticizer was used to disperse GO (PC@GO). This study uniquely divided PC into two parts, with one modifying GO and the other acting as a water-reducing agent, to explore the effects on GO dispersion and analyze the rheological, carbon emission, mechanical, and hydration properties of cement paste. The experimental results show that the dispersion of GO modified by PC was improved, resulting in a significant enhancement in the performance of the cement paste containing PC@GO. The flexural and compressive strength of cement paste containing PC@GO₄ cured for 7 days increased by 23.7% and 12.6%, respectively, meanwhile, the carbon-to-strength ratio (CI) decreased by 14.8%. In addition, the hydration acceleration period shortened by 7.50%, and the water absorption and porosity of the cement paste containing PC@GO₄ decreased by 35.2% and 45.3%, respectively. Incorporating PC@GO into cement paste significantly enhances the dispersion of GO, substantially improves its mechanical properties, and positions it as a promising solution for the development of high-performance cementitious materials. Full article

With the rapid advancement of 3D printing technology in low-carbon construction, the constructability of 3D printing materials has increasingly garnered attention. The constructability of these materials is intrinsically linked to their rheological properties. Therefore, this paper investigates the impact of additives, specifically hydroxypropyl methylcellulose (HPMC) and polycarboxylate superplasticizer (PCE), on the rheological properties of materials. The findings indicated that HPMC significantly increased both shear stress and apparent viscosity while also enhancing the thixotropic loop area. In contrast, PCE was found to reduce viscosity and yield stress, thereby improving fluidity and plasticity. The judicious incorporation of PCE (less than 0.003) and HPMC (less than 0.002) can enhance the rheological properties of the printing material, thereby improving the stability and interlayer bonding characteristics of the 3D printing structure. However, an excessive amount will result in a reduction in fluidity and cohesion, adversely impacting the printing quality. At this stage, the occurrence of cracks increases, which is detrimental to interlayer adhesion. Therefore, the judicious control of the proportions of PCE and HPMC can enhance the fluidity and viscosity of the material, thereby improving interlayer bonding strength and print quality. Full article