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In this study, three hydration heat controlling materials (HHCMs), respectively, containing pure hydroxyl (polyvinyl alcohol, PVA), carboxylic (polyacrylic acid, PAA) and ester groups (maleic acid-ethylene glycol ester, P(MA-EG)) were synthesized and mixed with cement-based materials, and the hydration heat and setting time of cement pastes and the SEMI adiabatic temperature rise and strength of mortars were tested. The results showed that PAA and P(MA-EG) reduced the peak value of hydration exothermic rate by 77.45% and 62.28%, respectively, and prolonged 54.14 h and 15.56 h, respectively. Mechanism studies showed that HHCMs containing carboxylic or hydroxyl groups adsorbed on cement particles by Ca2+ complexation, while HHCMs containing ester groups hydrolyzed to carboxylic groups in alkaline cement pastes, which hydrolysis rate changed with the hydration temperature of cement-based materials to regulate the hydration process. This study aims to provide technical feasibility and theoretical basis for exploring new avenues of synthesizing HHCMs with different functional groups. [ABSTRACT FROM AUTHOR]

Reducing or eliminating cracks caused by shrinkage of cementitious materials remains a daunting challenge for construction engineers. Drying shrinkage and autogenous shrinkage are the main shrinkage types in the service process of cement-based materials, which have a great impact on engineering applications. If cracks in concrete generate by drying or autogenous shrinkage, the mechanical properties, water resistance and durability of concrete will be also affected. It is an effective method to use chemical admixtures to inhibit the shrinkage of cement-based materials. Polycarboxylate plasticizer (PCE) is an important chemical admixture in cement-based materials and is widely used in practical engineering. It can bring great value by reducing the shrinkage effect through molecular design. Through our innovative design, a series of shrinkage-reducing polycarboxylate superplasticizers (SRPs) were synthesized, their molecular structures were confirmed by Fourier transform infrared spectroscopy (FTIR) and their molecular properties were determined by gel permeation chromatography (GPC). Furthermore, the shrinkage performances at different ages of the mortars containing the synthesized SRPs with different structures were systematically evaluated. The results showed that compared with the blank sample, the dry shrinkage rate and free shrinkage rate of the mortars containing SRP decreased by over 20% and 15%, respectively. Additionally, the shrinkage rates of the mortars containing SRP were significantly lower than that of the mortar containing conventional PCE, and moreover, the water-reducing performance was improved compared to conventional PCE. Based on the experimental results of surface tension and evaporation rate of different SRP solutions, the mechanism of the shrinkage-reducing effect was probed, as expected to provide guidance for the design and development of new shrinkage-reducing admixtures. [ABSTRACT FROM AUTHOR]

A series of novel comb-like poly(butyl acrylate)-g-poly(dimethylaminoethyl methacrylate) (PBA-g-PDMAEMA) with different side chain lengths were designed and successfully synthesized by the "first main chain then side chain" method. Infrared Spectroscopy (IR), 1H Nuclear Magnetic Resonance (1H NMR), and gel permeation chromatography (GPC) were used for structural confirmation and molecular weight characterization. This polymer exhibited responsive behavior from hydrophilicity to hydrophobicity under the alkaline environment of cement-based materials, with the contact angle of 105.6°, a decreased evaporation rate, and a hydrophile–lipophile balance (HLB) value. A significant internal hydrophobic effect on cement mortar was shown in the water absorption rate, which decreased by 75.2%, and a dry shrinkage-reducing rate of more than 30%. Furthermore, this polymer can effectively slow the exothermic rate, reduce the heat release, and delay the exothermic peak of cement hydration. It was interesting that these properties showed a direct correlation with the side chain length of the comb polymer. The aims of this study are to provide a new avenue to synthesize polymers with the spontaneous hydrophilicity–hydrophobicity transition in the cement system, achieving excellent internal hydrophobicity of cement-based materials, and to offer a promising alternative to resist external erosion for improving the durability and service life of cement-based materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel PCE (ISC-PCE) with ionic side chains was elaborately designed and synthesized. • Good plasticizing and retention capacities were shown for wide potential applications. • Larger R h and more adsorption sites led to a gentle and continuous adsorption mode. • Introducing ionic groups into PCE side chains can greatly thicken the adsorbed layer. • Particularly designed "brush" conformation helped to improve the dispersion stability. A novel dispersant with ionic side chains (ISC-PCE) for cement slurries was elaborately designed and prepared by a simple two-step method and its molecular structure was proved. The performance test results showed that the cement paste containing ISC-PCE exhibited stronger fluidity retention (about 79.6 % after 3 h), longer free settling time (more than 3 h) and fewer flocculating structures, which presented significant dispersing stability. Furthermore, the working mechanism of ISC-PCE to cement particles was also probed via molecular conformation, adsorption, complexation ability, zeta potential and adsorbed layer measurements. It is interesting that the introduction of ionic side chains into conventional dispersant-polycarboxylate superplasticizer (PCE) molecules can achieve gentle and continuous adsorption and increase the adsorbed layer thickness (increased by 103.1 % compared to conventional PCE). The aim of this study is to offer a promising pathway to synthesize a novel PCE endowing outstanding workability stability and great rheological improvements to cement pastes by innovative molecular design. This PCE with ionic side chains has enormous promises as an effective substitute to conventional PCE with nonionic side chains, particularly in the cement paste systems with strict requirements on slump retention. [ABSTRACT FROM AUTHOR]

In the synthesis of functional polycarboxylate superplasticizers (PCEs), ester monomer was usually used as small monomer or macromonomer. However, there were few studies on the co-introduction of small ester monomer and ester macromonomer into one PCE molecule and its effects. In this study, it was found an interesting behavior of competitive hydrolysis between these two ester monomers in diester PCE, which performed higher fluidity of cement paste, greater adsorption amount and shorter prolongation of the induction period of cement hydration due to the competitive hydrolysis. Furthermore, the kinetics of hydrolysis and adsorption of the diester PCE were probed, and the rate order was: ester macromonomer < small ester monomer < diester monomers. This study aims to innovatively reveal the special behavior and mechanism of competitive hydrolysis of PCE using diester monomers in cement-based materials and to provide a theoretical basis for enriching molecular design and innovative application of functional PCEs. [Display omitted] • First study on the competitive hydrolysis behavior of PCE having complex diester. • Competitive hydrolysis occurred between small ester monomer and ester macromonomer. • The kinetics of hydrolysis and adsorption of the diester PCE were established. • Better performances in adsorption and dispersibility of diester PCE in cement paste. • Competitive hydrolysis helped reduce the prolongation of hydration induction period. [ABSTRACT FROM AUTHOR]

To solve the problem of high viscosity for fresh concrete especially high-grade concrete, a novel viscosity-reducing type of polycarboxylate superplasticizer (PCE) was synthesized based on innovative design of molecular structure, and also was characterized to confirm the designed molecular structure. The rheological performances of cement paste and fresh concrete containing synthesized PCE were probed, which were analyzed by means of surface tension, adsorption behavior and zeta potential. The plastic viscosity showed a good correlation with T50 and V-funnel time according to mesomechanics process model. Moreover, the investigation of working mechanism interestingly showed that lowering molecular weight and side chain length and introducing hydrophobic groups can achieve improved dispersion capacity and viscosity-reduction effectiveness. The aim of this study is to provide a promising avenue to synthesize PCE with superior workability and viscosity-reducing performance in fresh concrete. This new type of PCE can be used as a viscosity-reducing agent in concrete engineering. [ABSTRACT FROM AUTHOR]

• A novel sulfonate-modified PCE was synthesized based on innovative molecular design. • Sulfonate modification on the side chains of PCE can enhance the sulfate tolerance. • Effects of competitive adsorption, ionic strength and conformation were studied. • Good performance retention and stability were shown for solving compatibility problem. • Many quantitative evaluation indexes for sulfate tolerance of PCE were established. A novel polycarboxylate superplasticizer (PCE) was synthesized by graft copolymerization between acrylic acid (AA) and end-functionalized poly (allyl sulfonate) (PALS) to produce comb polymer, i.e. PAA-g-PALS. The molecular structure was confirmed by Infrared Spectroscopy (IR) and 1H Nuclear Magnetic Resonance (1H NMR), and the molecular properties were characterized by Gel Permeation Chromatography (GPC). The conventional PCE with comb structure using isobutenyl polyethylene glycol (IPEG) as side chains (i.e. PAA-g-IPEG) was also synthesized to explore the effect of the side chain on the PCE performances. The fluidity and its retention, rheological properties, hydrodynamic radii (R h), adsorption behavior and zeta potential of the cement pastes containing PAA-g-PALS or PAA-g-IPEG were comparatively tested. It was found that this designed "sulfonate modified PCE" exhibited stronger dispersing stability and sulfate tolerance to cement paste and less sensitive to the sulfate competitive adsorption and the increase in ionic strength. Based on the above results, the evaluation method (the sulfate resistance index of PAA-g-PALS was increased by 24% as compared to that of PAA-g-IPEG) was innovatively established and the mechanism of sulfate resistance was clarified in detail. The purpose of this research is to offer an avenue with great potentials to synthesize a novel PCE with excellent workability retention and sulfate tolerance in fresh cement pastes. This sulfonate-modified polycarboxylate superplasticizer has great potentials as a viable alternative to conventional PCE, especially in some harsh cement systems. [ABSTRACT FROM AUTHOR]

• A novel comb-structural PMA-g-PVA was synthesized and used as a promising dispersant. • Functionalization of PVA can greatly enhance its thermal stability and dispersibility. • Good plasticizing and retention capacities were shown for wide potential applications. • Established a guiding equation for regulating the side chain length of comb polymer. • Innovative design on molecular topological transformation helped PVA performances. A novel dispersant for cement slurries or other suspensions was synthesized by graft copolymerization between maleic anhydride (MA) and end-functionalized poly(vinyl alcohol) (PVA) to produce comb polymer, i.e. PMA-g-PVA. The chemical structure was characterized by 1H Nuclear Magnetic Resonance (1H NMR), Infrared Spectroscopy (IR), Gel Permeation Chromatography (GPC), alcoholysis degree and element analysis. This functionalization of PVA can significantly enhance its thermal stability and dispersibility. The evaluations of PMA-g-PVA and PVA in cement slurries were comparatively discussed in detail. The results showed that PMA-g-PVA performed well in dispersing and dispersing retention capacities, presenting more excellent fluidities of cement slurry (~200 mm) with maintenance of >85% within 3 h, due to its strong ability of breaking large flocculated structures of cement particles to fine size and homogeneous dispersion. This new type of functionalized PVA may be introduced as a promising candidate for the rheology modifying superplasticizer in slurry or colloid materials. [ABSTRACT FROM AUTHOR]