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• "Si-O-Si" could refine the pore structure together with hydration products to improve the anti-efflorescence of the coating. • KH-560 could improve the compatibility between PA and PDMS, reducing the deterioration of mechanical properties by PDMS. • The efflorescence area of the modified-coating containing MP and 0.3 wt% SA was only 1.58%. The objective of this paper was to prepare a novel type of anti-efflorescence cement-based coating with excellent mechanical properties using the modified polyacrylate emulsion (MP) and silicon-aluminum based powder (SA), and provided an optimum proportion. Silica sol (SS) and polydimethylsiloxane (PDMS) were selected as modified components to incorporate into polyacrylate emulsion (PA). The synergistic effect of MP and SA on the tensile strength, water absorption, hydration process, microstructure and anti-efflorescence property of cement-based coatings were investigated. The research results demonstrated that the tensile strength and waterproof in coating containing MP and 0.3 wt% SA were increased by about 73.4% and 52.1%, respectively, compared with the reference sample. The reason could be attributed to the densification of the internal structure due to the formation of "Si-O-Si" structure and pozzolanic effect of SA. In addition, the hydrophobic PDMS can hinder the migration of water and salt, thereby limiting the diffusion of alkali ions outward. Hence, the efflorescence area of the modified-coating was decreased to 1.58%. [ABSTRACT FROM AUTHOR]

As the main product of hydration reaction of common Portland cement, calcium silicate hydrate (C-S-H) gel is a porous gel system containing capillary and gel pores. These channels act as transport channels for water molecules and ions in the cement system. The diffusion of water molecules and ions through C-S-H gel channels has significant effects on the strength, shrinkage, creep, chemical and physical reactions of the cement system. Polymer can modify cement-based materials and improve their ionic permeability resistance. In this study, emulsified asphalt powder (EAP) and vinyl acetate ethylene copolymer (VAE) redispersible polymer powder was added into the Portland cement mortar as admixtures, respectively. The influence of redispersible polymer powder on the transportation and erosion mechanism of ions in cement mortar was investigated by analyzing the pore structure, compressive strength ratio, chloride ion permeability depth and micromorphological of cement mortar. The adsorption and diffusion behaviors of ions with different concentrations and water molecules were explored by molecular dynamics simulation, and the physiochemical reactions between ions and hydration products during the transport process in cement-based materials were comprehended. • Influence of polymer on the ion permeability of cement mortar was studied. • The adsorption and diffusion behaviors of ions and water molecules were studied by molecular dynamics simulation. • The effect of EAP on chloride ion permeability resistance is obviously better than VAE redispersible polymer powder. [ABSTRACT FROM AUTHOR]

Various problems are often encountered during the backfilling process of deep foundation pits. The development of low-cost and efficient solidified materials for the preparation of fluidized solidified soil is currently an ideal solution. This article used industrial solid waste (granulated blast furnace slag, fly ash, carbide slag, etc.) as the main raw material to study the hydration hardening properties of solidified materials and the construction feasibility of fluidized solidified soil prepared from solid waste materials. The results are as follows: Compared with cement-based materials, solid waste-based solidified materials had lower early activity. The cumulative heat release within 72 h was less than 200 J/g. Different solid wastes, such as fly ash and carbide slag, had different effects on the properties of solidified materials. Overall, they had the potential to prepare fluidized solidified soil. The prepared fluidized solidified soil had a fluidity greater than 350 mm, a 28d compressive strength greater than 3 MPa, and exhibited good workability and excellent mechanical properties. Hydration products such as C-S-H and AFt were filled in the soil structure. The 28d compressive strength well above the design requirements of general engineering projects. Meanwhile, the prepared fluidized solidified soil had good adaptability to conventional water reducers (fluidity could be increased by more than 40%) and early strength agents (1d compressive strength could be increased by more than 60%). • Use fluidized solidified soil to solve the problem of backfilling deep foundation pits. • Utilize the synergy between industrial solid waste to improve the solidification effect. • Establish the connection between solidified materials and fluidized solidified soil. • The adaptability of fluidized solidified soil to admixtures was studied. [ABSTRACT FROM AUTHOR]

How to simply and effectively improve the mechanical properties and UV resistance of polymer-modified cement-based coatings is the key to expand its application field. In this study, a novel type of polyacrylate (M-PA) emulsion modified by polydimethylsiloxane (PDMS), colloidal nano-silica (CNS), and 3-Glycidyloxypropyltrimethoxysilane (KH-560) was prepared based on the response surface methodology (RSM) to achieve composition optimization. In addition, the effect of M-PA emulsion on the mechanical properties, impermeability, microstructure, and UV resistance was comprehensively studied. The research results demonstrated that the tensile strength and hydrophobicity of M-PA emulsion film were the best when the content of CNS, PDMS and KH560 was 16–17%, 6–7% and 0.075–0.12%. The reason can be attributed to the chemical combination of modifier and the formation of 'Si-O-Si' of three-dimensional network structure in M-PA emulsion. In comparison with a coating containing unmodified PA emulsion, the bond and tensile strength of M-PA modified samples were increased by 29% and 43%, respectively, while the water absorption was reduced by 28% due to the refinement of microstructure. As a result, the hydrophobic film of the modified coating was still intact after UV-aging for 1000 h. • The optimal ratio of M-PA emulsion was determined by RSM. • Organic-inorganic cross-linked 'Si-O-Si' network improved mechanical properties of the coating. • PDMS enhances the UV resistance of the coating. [ABSTRACT FROM AUTHOR]