To address the issue of pavement cracking due to brittle concrete in road and bridge engineering, this study explores the use of high–ductility magnesium phosphate cementitious concrete (HD–MPCC) for rapid repairs. The deformation and frost properties of HD–MPCC are analyzed to assess its suitability for this application. Deformation properties were tested for HD–MPCC specimens cured in both air and water. Subsequent tests focused on the frost performance and mechanical properties after freeze–thaw cycles. A mercury penetration technique was utilized to examine the pore structure. The findings reveal that the expansion deformation of HD–MPCC increases with curing age in both air and water conditions, and the quantitative relationship between the expansion deformation and curing age of HD–MPCC was analyzed. Additionally, the freeze–thaw cycles led to a decrease in mass loss, the relative dynamic elastic modulus, the ultimate tensile strength, the ultimate tensile strain, the flexural strength, and the peak deflection. The volume fraction of harmless and less harmful pores gradually decreased as the freeze–thaw cycle increased, while the volume fraction of more harmful pores increased, resulting in a decrease in the strength, ultimate tensile strain, and peak deflection.

This study analyzes the mechanical properties of high ductility concrete (HDC) under different ambient temperatures to provide a parameter basis for the design of HDC bridge deck link slabs. Five temperatures (−30, 0, 20, 40, and 60 °C) were designed to investigate the compressive, tensile, and flexural properties of HDC after temperature treatment and analyze the pore structure. The results show that, compared with the HDC performance at room temperature (20 °C), the compressive strength, ultimate tensile strength, and flexural strength decreased after treatment at low temperatures (−30 and 0 °C), while the strength increased after treatment at high temperatures (40 and 60 °C). After experiencing low- and high-temperature treatments, the ultimate tensile strain and ultimate deflection of the HDC increased. The tensile and flexural failures of the HDC exhibited multiple cracking, and the stress–strain/deflection curve showed a strain/deflection hardening stage. The tensile constitutive relationship can be simplified as a bilinear two-stage relationship. As the temperature increased, the porosity of harmless and less harmful pores in HDC gradually increased, while the porosity of harmful and more harmful pores gradually decreased, resulting in an increase in HDC strength. Based on the influence of temperature on HDC properties, design parameters for the HDC bridge deck link slab structure are proposed.

To comprehensively utilize industrial by-products of gypsum while reducing the consumption of natural river sand, this experiment was conducted to prepare gypsum-based sandless self-leveling (PGSL) materials by using phosphorus-building gypsum (PBG) and portland cement (PC) as gelling raw materials with the addition of polycarboxylate superplasticizer (PCE), cellulose ethers (CE), and retarders. However, employing phosphogypsum as the source material results in a significant 30 min fluidity loss in the gypsum-based self-leveling system. Therefore, to enhance the flow characteristics of gypsum self-leveling, sodium gluconate was chosen for usage in this research. The impact of single and compound mixing of protein-based retarder (PR) and sodium gluconate (SG) on gypsum-based sandless self-leveling materials was evaluated in terms of heat of hydration analysis, pore structure, fluidity, strength, and setting time. According to the experimental findings, it was possible to considerably decrease the fluidity loss of gypsum-based sandless self-leveling materials, postpone the setting time, boost strength, and enhance pore structure when combined with 0.4% SG and 0.03% PR.