The aim of this study was to analyze the influence mechanism of aeolian sand on the mechanical property of concrete and establish the time‐varying compressive strength model. Test studies on the development of concrete’s compressive strength with aeolian sand from the Mu Us Desert were carried out. Influence mechanism of aeolian sand on the strength of concrete was revealed by using the nuclear magnetic resonance (NMR) to analyze the pore ratio and structures of aeolian sand concrete (ASC) and using the X‐ray single crystal diffraction (XRD) to calculate the relative contents of hydration products semiquantitatively. Results show that the strength first increases and then decreases with the increase of aeolian sand content, where 20% was the best replacement ratio. With less than 20% content, it promoted the strength by changing the pore structure of concrete and accelerating the cement hydration speed based on its filling effect and chemical activity; when the content was more than 20%, it led to a decrease of strength because of an increase of harmful pore ratio and a weakening of the interface transition zone (ITZ), where the stress concentration and damage when loading are easier to occur. At last, a time‐varying compressive strength model of ASC considering the harmful pore ratio variation and heterogeneous nucleation effect was established based on the discussion, published date, and American Concrete Institute (ACI) model, which agrees well with the experimental results and can easily predict the strength of concrete.

The aim of this study was to reveal the macroscopic and mesoscopic deterioration behaviors of concrete under the coupling effect of chlorine salt erosion and the freezing–thawing cycle. The rapid freezing–thawing test was carried out in a 5% chlorine salt environment. The macroscopic characteristics of concrete were analyzed by testing the mass, the relative dynamic modulus of elasticity, and the compressive strength of concrete under different freezing–thawing cycles. Using CT scanning technology and three-dimensional reconstruction technology, the pore structure, CT value, and surface deviation of concrete before and after freezing–thawing were analyzed. Based on the changes of solid volume, pore volume, and solid CT value of concrete, the calculation method of relative CT value was proposed, and the damage model was established with relative CT value as the damage variable. The results demonstrate that the mass loss rate decreases in the beginning and then increases in the process of chlorine salt erosion and freezing–thawing, and the smaller the concrete size, the greater the mass loss rate. The relative dynamic modulus of elasticity decreases gradually, slowly at the initial stage and then at a faster rate, and the compressive strength loss rate increases gradually. The pore quantity, porosity, and volume loss rate of concrete increase in a fluctuating manner, whereas the relative CT value decreases. The comprehensive analysis shows that the chlorine salt frost resistance of concrete is negatively related to the water-cement ratio when the freezing–thawing cycle is fixed. The damage model could better reflect the freezing–thawing damage degree of concrete with different water cement ratios, and the damage evolution process is well described by the Weibull function.

Aeolian sand (AS) can become a green resource for concrete after the reasonable utilization. Study the evolution of AS concrete (ASC) capillary water absorption (CWA) under freeze–thaw (FT) conditions is of great significance for its popularization and application. One-dimensional (1D) CWA test was performed to analyze the effects of AS and freeze–thaw cycling (FTC) on concrete water absorption characteristics. Pore relative saturation (PRS) and pore saturation were defined to reveal the influence mechanism of AS content on concrete water absorption under FT conditions and predict the moisture distribution in damaged ASC combining with the capillary mechanics theory. The results showed that concrete frost resistance increased with increased AS content and the optimal frost resistance achieved with 100% AS replacement despite its low strength. The initial water absorption rate (WAR), pore saturation, and saturation speed of the ASC decreased with increased AS, while the PRS increased with low AS content but decreased with excessive AS. The water absorption depth increased with increased mass and dynamic elastic modulus loss rates. The mechanism regarding why excessive AS improved concrete frost resistance lay in its internal pore structure and large pore ratio, which reduced pore content that can easily absorb water, enclosed a higher volume of air bubbles, and easily formed "air locking," thereby increasing water transmission resistance and forming long transmission paths during the process of CWA.

The aim of this study is to explore the feasibility of coal gangue (CG) fine aggregate replacing natural sand, and realize the resource utilization of solid waste in concrete materials. The coal gangue concrete (CGC) is prepared with the CG replacement of 0%, 5%, 10%, 15%, 20%, 50% and 100%, the influence of CG replacement on the slump, bulk density, compressive strength and pore structure of concrete is analyzed, and the influence mechanism is revealed combining with the scanning electron microscope (SEM), nuclear magnetic resonance (NMR) and X-ray diffractometer (XRD). The results shows that the optimal mechanical property is achieved with 10% CG replacement, which is 10.1% higher than that of the ordinary concrete. The influence mechanism is that it accelerates the hydration reaction of cement, improves the interfacial transition zone (ITZ), increases the harmless pores percentage and reduces the more harmful pores percentage. The research provides theoretical support for the high value utilization of solid waste in mining area.

Influence of pore structure characteristics on the strength of aeolian sand concrete To investigate the influence of the pore structure characteristics of aeolian sand concrete on the mechanical properties, macroscopic mechanical tests of aeolian sand concrete were performed under different conditions, and the influences of the water-cement ratio, sand ratio, and aeolian sand replacement rate on the compressive strength were analysed. The internal microscopic pore structure was characterised using scanning electron microscopy and nuclear magnetic resonance. The impact of pore structure parameters on compressive strength was determined by the grey relational entropy, and a pore structure-strength model was established.