Experimental Study On Cement-based Grouting Material Mechanical Properties Under Freezing-Thawing And Chloride Penetration

In Qinghai salt lake area, due to its special geographical environment, the local construction structures are suffering severe seasonal freeze-thaw cycles and chloridion penetration. The iMPact of freeze-thaw cycles and chloridion erosion promotes and progresses each other which shortens the lifespan of concrete structures in the salt lake area and its surrounding areas. Therefore,it is extremely urgent to improve the concrete structures resistance in the salt lake area. This thesis attempts to develop a cement-based grouting material which can resist chloridion erosion, so as to protect the concrete from chloridion penetration and freeze-thaw damage and improve the durability of concrete structures.This thesis did a systematic research on the material selection, mixture ratio design and durability of cement-based grouting material, analyzed and optimized each factor’s iMPact on the grouting material’s performance and obtained certain achievements which will be very important significance for the future engineering application and research. The main research contents and achievements are as below:(1) Using orthogonal method, research was conducted on water- binder ratio, binder- sand ratio, silica fume, fly ash expanding agent and water reducing agent’s iMPact to the fluidity and strength of Cement-based grouting material, obtained the factors that have obvious iMPact to the performance of the grouting material and initial optimized mixture ratio parameters for the grouting material.(2) By single variable test, in-depth research was done on water- binder ratio, binder- sand ratio, silica fume, fly ash, and water reducing agent’s iMPact to the compressive and flexural strength of cement-based grouting material, further optimized mixture ratio parameters, and obtained cement-based grouting material which has better physical and mechanical performance. In addition, the using of certain amount of defoaming agent not only improved the surface property but also improved the strength of the grouting material which obtained good modification result.(3) The anti-freeze-thaw cycle tests were conducted for cement-based grouting material in 10%、15% and 20% concentration salt solutions. The tests results have shown that the strength and quality of the grouting material reduces as the times of freeze-thaw cycles increase. In the 15% concentration salt solution, the strength and quality loss ratio is higher. The 20%concentration salt solution effectively lowered the freezing point which is beneficial for the antifreeze of the test samples. However, the test samples’ freeze-thaw loss ratio in the salt solution is higher than in the water.(4) Long period immersion tests were done for cement-based grouting material test samples in 10%, 15% and 20% concentration salt solutions. The results have shown that as immersions time increases, the corrosion resistant coefficient of the test samples will firstly increase and then reduce, and will reduce as the salt solution concentration increases. After immersion in 20% salt solution for 9 months, the chloridion penetration depth of the test samples is 3.20 and the erosion ratio obviously reduce which means the grouting material has good chloridion penetration resistance.