The large temperature difference condition in Northwest China threatens a myriad of concrete structures during construction, with the daily temperature varying by around 40 °C. To investigate the macro-mechanical properties and microstructural characteristics of concrete containing different amounts of mineral admixtures under such harsh conditions, this investigation used an environmental chamber to simulate a saline soil erosion environment with a large temperature difference. Four types of concrete containing different proportions of fly ash and slag were prepared and exposed in the environmental chamber with a daily temperature change of −5~40 °C to investigate their compressive strength, flexural strength, and fracture properties. Moreover, the X-ray diffraction (XRD) characteristics, microscopic morphological characteristics, pore structure characteristics, and post-erosion chloride ion distribution characteristics were also observed and recorded. Results showed that the mineral admixture could improve the early strength development of the concrete and effectively improve the fracture performance of the concrete. The average compressive strength growth rate of concrete from day 3 to day 14 was 83.25% higher than that of ordinary concrete (OC) when 15% fly ash and 15% slag were added. In addition, the fracture energy of the concrete was maximized when 15% fly ash and 20% slag were added, which was 50.67% higher than that of OC; furthermore, the internal compactness and pore structure were optimized, and the resistance to saline soil erosion was strong. This provides a basis for the practical application of compounded mineral admixture-modified concrete in an arid environment with a large temperature difference and saline soil erosion.

The climate in the Central Asian area is extreme dry, with a large temperature difference between day and night, and the concrete is easy to crack during the construction period under the conditions of traditional external curing. Therefore, this study concerns understanding the application of internal curing materials in a dry and large-temperature-difference environment. The effects of three internal curing materials, namely, Super Absorbent Polymer (SAP), Light Weight Aggregate (LWA) and Perforated Cenospheres (PCs), on hydration and pore structure characteristics of concrete were investigated. Scanning electron microscope and x-ray diffraction were used to observe the microscopic morphology and physical phase composition of concrete, and the evolution of pore characteristics was analyzed using mercury injection apparatus to explore the mechanism of pore structure refinement. Results show that the pores formed by the release of water provide space for the accumulation of hydration products, thereby accelerating the formation of ettringite crystals. Results indicate that the continuous release of internal curing materials allows the interior of the concrete to continue to be hydrated, which greatly promotes the overall hydration of the cement. The effect of supplementary cementitious materials (GGBS, FA) and implications of large-temperature-difference environment on concrete durability are discussed.