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Polycarboxylate ether (PCE) superplasticizers are widely used in concrete, but in some cases, PCE aggravates the occurrence of cracks. This study evaluates the shrinkage reduction and plasticizing properties of a newly synthesized shrink-reducing polycarboxylate polymer (KH-SRPC) modified with ester and silane groups. When the KH-SRPC was implemented at a dosage of 0.3% by weight of cement, the adsorption capacity on the surface of the cement particles and the spreading diameter of the cement improved with respect to traditional PCE. Furthermore, the autogenous shrinkage and drying shrinkage of the mortar containing KH-SRPC were also investigated. When the KH-SRPC content was 0.2% of the weight of the cementitious material, the autogenous shrinkage of the KH-SRPC mortars at 3 and 7 days was reduced by 72.6% and 43.5%, respectively. The drying shrinkage of KH-SRPC mortars decreased by 38.3% at 3 days, 39.0% at 7 days, 39.1% at 14 days, and 35.7% at 28 days. It was found that KH-SRPC changed the pore structure of the solidified mortar, reduced the surface tension of the pore solution, and slowed down the rate of hydration, thereby reducing the total shrinkage of the mortar system. [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]

• The construction of inherent reactive XPSF surface by ultraviolet-zone. • The fabrication of covalently bonded XPSF/mortar interfaces. • The thorough investigation of the reactions between APTES and XPSF surface. The inert surface of extruded polystyrene foams (XPSF) was activated by ultraviolet-ozone (UVO) for the first time to improve the interfacial compatibility with mortar. From the structural analysis (X-ray photoelectron spectroscopic (XPS) and contact angle (CA)), it was suggested that a 10 min UVO exposure was efficient enough to introduce oxygen-contained elements (such as carboxyl groups) upon the obtained UVO-XPSF surface, leading to the increased bonding strength (BS) from 0.058 MPa of neat XPSF/mortar composites to 0.088 MPa. Then, 3-aminopropyl triethoxysilane (APTES) was selected as the promoter to further enhance the BS value of XPSF/mortar composites. The presence of the silane was confirmed by CA, Fourier transform infrared-attenuated total reflection (FTIR-ATR) and XPS. By optimizing the reaction conditions (activation and reaction time: 7 and 3 min, concentration of APTES: 2% and pH value of the silane solution: 10), a maximum BS of 0.168 MPa could be obtained. Through the mechanism analysis, it was demonstrated that APTES acted as a chemical bridge that covalently jointed XPSF by the formation of amide peptide and inorganic mortar by the condensation of silanols. [ABSTRACT FROM AUTHOR]

Self-healing cementitious materials are a promising means for ensuring sustainable concrete infrastructure and promoting long-term service lives. To obtain microcapsules that are versatile in varying environments, in this study, absorbing microcapsules with calcium alginate as the shell and epoxy resin as the core were prepared. The absorbing microcapsules exhibit self-healing and can reduce the shrinkage of cementitious materials. Volume changes of the microcapsules in the hardened paste with increasing hydration age were observed using three-dimensional X-ray computed tomography. In the hardened cement paste with a water-cement ratio of 0.29, the absorption of the microcapsules lasted for several days, and the release of water lasted for 28 days. The absorption of microcapsules affected the fluidity of cement paste, and it was significantly weakened and delayed due to the lower absorption rate. The addition of absorbing microcapsules significantly reduced the autogenous and drying shrinkage of mortars. For microcapsules with a core content of 55% added at 3.5% of cement weight, autogenous shrinkage was almost eliminated. Most importantly, the addition of absorbing microcapsules could achieve a certain degree of recovery of compressive strength as well as satisfactory recovery of impermeability in dry and wet environments. [ABSTRACT FROM AUTHOR]

• Effective modification of extruded polystyrene foam (XPSF) by the ultraviolet-ozone. • Amphipathic silane coupling agents as the adhesion promoters between XPSF and mortar. • A significant improvement on the interfacial strength of XPSF/mortar. • The chemical linkages can be induced by different kinds of silanes. The inert surface of extruded polystyrene foam (XPSF) was activated by the ultraviolet-ozone (UVO) irradiation, followed by the surface coupling reactions with γ-mercaptopropyl trimethoxysilane (MPTMS) and vinyl triethylsilane (VTEO) to improve the interfacial affinity between the organic XPSF and inorganic mortar. The reaction conditions (including reaction time, concentration and pH of the silanes) were thoroughly investigated in order to reach the maximum bonding strength (BS) of XPSF/mortar composites. It was suggested that the presence of MPTMS could increase the BS value from 0.04 MPa to 0.178 MPa (reaction time: 10 min, concentration of MPTMS: 2% and pH value of the silane solution: 4). For VTEO, the maximum BS value reached to 0.140 MPa (activation and reaction time: 7 and 3 min, concentration of VTEO: 5% and pH value of the silane solution: 7). According to the mechanism analysis, the thiol groups in MPTMS have the strongest reactivity with activated XPSF surface after UVO exposure, leading to the maximized interfacial strength between the organic insulation materials and inorganic mortar. [ABSTRACT FROM AUTHOR]

In this study, the impacts of CO 2 -absorbed triethanolamine solutions (TEA-CO 2) on the mechanical property, phase composition and micro-structure of cement mortars were investigated. The results showed that TEA-CO 2 addition increased the 1d, 3d, and 28d compressive strength by 47%, 19%, and 4%, respectively, which suggests a synergistic effect of triethanolamine and absorbed CO 2 on strength development of cement mortars. The enhancement is due to TEA-CO 2 accelerates hydration of aluminate and silicate phases in early age. TEA-CO 2 facilitated CaCO 3 formation to increase cement hydration degree and modify the pore structures. However, the hydration of silicate phases was delayed slightly by TEA-CO 2 at 28d. The above results provide theoretical support for further utilization of CO 2 in cementitious materials. • Effect of TEA-CO 2 on strength development of mortars was investigated. • TEA-CO 2 addition increases flexural and compressive strength of mortars. • TEA-CO 2 accelerates the hydration of aluminate phase and silicate phase at early age. • A synergism of cement hydration and carbonation in the presence of TEA-CO 2 was proposed. [ABSTRACT FROM AUTHOR]

UV curable organic-inorganic hybrid (OIH) coatings were used to modify the extruded polystyrene foam (XPSF) surfaces to increase the bonding strengthen (BS) of XPSF/mortar composite (XMC). OIH coatings contained polyurethane acrylate, hexanediol and nanoparticles with different dimensions. With the addition of nano-SiO 2 and halloysite nanotubes, the BS-D (BS in dry state) & BS-W-2H/7D (BS in wet state after 2-hour/7-day drying) values for modified XMC were increased from 0.050 & 0.039/0.047 MPa to 0.245 & 0.196/0.356 and 0.312 & 0.233/0.323 MPa. The chemical bonding between SiO 2 /-COOH from UV coating and hydration products in mortar improved the bonding state. [Display omitted] • Modification of XPSF surface by UV curable organic-inorganic hybrid coating. • The fabrication of chemical bonding for XPSF/mortar interfaces. • The investigation of the reactions between mortar and modified XPSF surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • The construction of reactive hydrophilic XPSF surface by the surface curing of UV curable adhesives. • The fabrication of chemical bonded XPSF/mortar interfaces. • The thorough investigation of the reactions between cured UV adhesive coating and XPSF surface. The hydrophobic surface of extruded polystyrene foams (XPSF) was modified by UV curable adhesives to enhance the interfacial bonding strength (BS) with mortar. The UV adhesive contained epoxy acrylate resin, acrylic acid and butyl acrylate (denoted as EAB). After EAB modification, the BS value in dry state (BS-D) increased from 0.050 MPa of unmodified XPSF with mortar to 0.210 MPa. Then, 3-aminopropyltriethoxysilane (APTES) was further introduced into EAB to form the water-resistant coatings (denoted as EABT) to enhance the BS value in wet state (BS-W). By optimizing the composition, the maximum BS-D and BS-W of 0.216 and 0.158 MPa in 7-day curing were obtained. The bonding mechanism illustrated that the modified XPSF was chemically bonded with mortar. [ABSTRACT FROM AUTHOR]

• The accelerated self-healing of cracks in cement mortars containing TEA was investigated. • The size of portlandite are greatly decreased by the addition of TEA in cement mortars. • The accelerated formation of CaCO 3 is responsible for the accelerated crack healing in TEA containing mortars. Mechanism of accelerated self-healing behavior of cement mortars incorporating triethanolamine (TEA) was investigated. The crack width in cement mortar specimens and the healing efficiency of cracks during immersion in water were quantitatively measured according to the Poiseuille's law. To reveal the working mechanism of TEA in the accelerated self-healing of cracks in cement mortars during water immersion, multi-techniques including X-ray diffraction (XRD), thermogravimetry (TG), nitrogen sorption isotherm and scanning electron microscopy (SEM) were employed to determine the changes in composition and microstructure of hydration products in the presence of TEA before and after water immersion. In addition, carbonation process of synthesized CH powder was studied. Results show that self-healing of the cracks in cement mortars during water penetration is a result of the continuous formation of CaCO 3 on the fractured surfaces. TEA addition visibly enhances the self-healing performance of cement mortars and a higher dosage of TEA leads to a higher self-healing efficiency, because of the accelerated precipitation of CaCO 3 on the fractured surface in mortars. TEA addition results in great morphological changes and increasing the surface area of portlandite as the second major hydration product of cement. Thus the carbonation process is notably accelerated in the mortars containing TEA. Moreover, the TEA-Ca2+complexation may promote the decalcification of C-S-H. [ABSTRACT FROM AUTHOR]