Experimental Study On Durability For The High Performance Concretre

Concrete structure is the most widespread type of structures used in national basic construction, but due to the poor durability of concrete, concrete delamination, damage and destruction are increasingly serious under bad condition, so high performance concrete (HPC) emerged. Aiming to keep the operable performance and mechanical properties of the concrete, emphatically improve its durability.This article studied the various performance of high performance concrete (HPC) using fly ash, silicon fume, polypropylene fiber for admixtures. These admixtures replaced the equivalent cement in different mixture proportion so as to make proportioning of concrete adjusted and optimized. Seventeen groups of proportioning were designed, experimental research on compressive strength, tensile strength and durability for every group. The main conclusions are as follows:(1) Mineral admixture as fly ash, silicon fume can well improve the performance of concrete, make it not bleeding,not segregating, good cohesiveness; Fly ash can increase the long-term strength of concrete, but silicon fume with high activity is in favor of early age strength of concrete; The admixture with certain proportion between the two can play additive effect, making strength in different ages increased; The addition of polypropylene fiber had no effect or a slight decrease on the strength of concrete, but will not cause greater damage.(2) The addition of fly ash and silicon fume can all enhance the different levels of impermeability of concrete, and silicon fume as finer particles is more favorable to improve the impermeability of concrete; if using a complex or a small amount of polypropylene fiber, it will cause better impermeability.(3) The more fly ash mixed with the more carbonation depth of concrete, and the more mixed of silicon fume the decreasing of carbonation depth, but the overall depth of carbonation is smaller, that can't cause protective layer of concrete in the destruction of nature.(4) A certain amount of fly ash or silicon fume can improve the frost resistance of concrete, but mixed with excessive will reduce the air content of concrete, resulting in frost resistance decreased. The amount of fiber are also suitable, too much can weak interface content, resulting in frost resistance decreased.(5) As for the shrinkage of the concrete, the fly ash can be appropriately reduce the value of shrinkage of every age, while the hydration of silicon fume is quite fast so as to be detrimental to shrinkage of concrete. In view of this, the admixture with certain proportion between the two or the addition of fiber can improve.(6) Durability of high performance concrete is a complicated issue, mineral admixture can be selected based on the requirements of different parts and different durability, so as to improve the targeted durability of concrete.