Long-term Service Performance Of Concrete Face For Earth-rock Dam In Cold Regions

The complex hydraulic environmental conditions in cold regions have brought great challenges to the construction and service of extra-high earth-rock dams.The deterioration of the performance of high-dam concrete materials in actual service is actually caused by complex physical and chemical long-term interaction.In this paper,based on the concrete slabs of extra-high dams in service in the cold region,the mix ratio optimization was carried out from the two dimensions of water-binder ratio and mixed mineral admixtures.The law and mechanism of performance degradation provide a theoretical research basis for guiding the construction and service of super-high earthrock slab concrete.The results are as follows:(1)Based on the slab concrete used in mid-high dams,the effects of gradients of water-binder ratio and blending of 5% silica fume,10% and 15% slag,and metakaolin on concrete slump,gas content,and compressive strength were investigated.The decrease of the rubber ratio leads to the decrease of the slump and air content of the fresh concrete,but the compressive strength of the hardened concrete increases.The slump and air content of the fresh concrete decrease with the addition of the admixture,but the compressive strength increases.A test method and test device that can simulate the effects of freeze-thaw,dissolution and load on the durability of concrete are proposed.(2)The mass loss rate of concrete in the durability test increases with the duration of the endurance test,and the ultrasonic velocity and volume resistivity decrease with time;the multi-factor coupling leads to more serious deterioration of the concrete performance,which exceeds the two-factor and single-factor The influence on the deterioration of concrete performance;combined with the slope of the evaluation index change curve,it was found that the freeze-thaw cycle in the multi-factor coupling test played a leading role in the deterioration of the durability of the concrete;taking the water-binder ratio of 0.39 as the benchmark,the water-binder ratio was found to be 0.34 The concrete and concrete with 10% metakaolin were stable in the durability test.(3)The percentage of calcium hydroxide and the relative crystallinity in panel concrete decrease with the increase of test factors.The effect of the multi-factor coupling test on the calcium hydroxide diffraction peak is greater than the two-factor and singlefactor tests.According to the SEM image,With the increase of test factors,obvious cracks and pores appear in the concrete.The three concretes with a water-binder ratio of 0.34 and 10% and 15% metakaolin have higher compactness,fewer cracks and pores,and perform stably in durability tests.