Aiming at the outstanding problem of concrete durability in cold and arid regions, the Datonghe-Qingwangchuan Diversion Project in Gansu Province, China, was used as a typical research area, and erosion products were determined by field sampling and laboratory XRD analysis. Three durability evaluation indices, namely, the mass loss rate, relative dynamic elastic modulus (RDEM), and compressive strength loss rate, were measured via indoor accelerated testing. Based on grey relational theory, a concrete durability evaluation model was constructed. The critical failure values of the three evaluation indices were introduced as a set of data to optimize the model and determine the grey relational degree of each group of concrete specimens under different working conditions. The results show that using the test results and the optimized grey relational analysis evaluation model, the concrete specimens mixed with an air-entraining agent have strong resistance to composite erosion. The durability of concrete specimens with an air-entraining agent content of 0.016% and fly ash content of 15% is better, and a high content (30%) of fly ash accelerates the damage of concrete specimens. The model calculations are consistent with the test results. This method can solve the problem of the durability of concrete specimens in the whole test cycle not being fully evaluated. The results of the study provide useful references for concrete mix proportion optimization and durability evaluation problems.

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Freeze-thaw harm is the major factor that reduces the durability of hydraulic concrete buildings at high altitudes and in cold regions. To solve the durability problem of hydraulic buildings in alpine regions, the study prepared sixteen groups of concrete specimens with different replacement ratios of iron ore tailings and recycled aggregate were prepared, and indoor deterioration accelerated tests were designed. Nuclear magnetic resonance (NMR) technology was used to analyze the pore distribution in the structure, and macro indicators of concrete mass loss rate and relative dynamic elastic modulus (RDEM), were selected. Combined with SEM, images, the frost resistance of iron ore tailings sand (IOT), with Recycled aggregate concrete (RAC), was explored. The final analysis shows that when only RCA is replaced, the frost resistance of RAC decreases with the increase of the RCA replacement rate. When only replacing IOT, the frost resistance of IOT concrete with a replacement rate of 50% is better than that of other replacement rates. In addition to ordinary concrete, the combination of 30% iron ore tailings and 30% recycled aggregate concrete (RAC3-IOT3) has good frost resistance. The mass loss of the RAC3-IOT3, specimen increased by 0.09% compared with ordinary concrete. From the microscopic level, with the addition of the dosage of RCA, the number of macropores (0.05∼1 μm) and microcracks (>1 μm) in concrete increased. After replacing the appropriate amount of iron ore tailings, the pore space structure of RAC was improved, and some harmful pores spaces were transformed into harmless pores. However, the combination of excess IOT, and RCA, does not improve the interface transition zone of RCA. From the micromorphology, with an increasing dosage of RCA, the bonding force between cementitious material and sand aggregate weakens and there are more pores. The combination of excess IOT, and RCA, does not improve the interface transition zone of RCA but will accelerate the spalling of surface mortar because of its small fineness. All things considered, RAC3-IOT3 is the most suitable concrete for high altitude and cold areas.