Study On The Mechanism Of Crack Generating Of High Strength Concrete And Crack Controlling

With many good properties, high strength concrete (HSC) is becoming the developing direction of modern concrete technology and extensively applied in many fields. But the questions of buildings cracking of HSC are very serious. It brings people a lot of trouble and unnecessary loss. So, to buildings, it is very important to enhance the quality of HSC anti-cracking property. Aiming at the main problems of HSC, we put forward that using expansive agent and fiber in HSC to compensate and limit the shrinkage. These measures can conquer the defects of HSC and make HSC possess excellent performances, such as the good workability and high flow ability.Based on above, the characteristics of hydration hardening process and microstructure of HSC as well as the interfacial layer between cement paste and coarse aggregate are investigated under low water cement ratio, high content superplasticiser and with one kind or more than one kind of mineral materials condition, the reaction mechanisms of different mineral materials are also discussed. The influence of mineral materials such as fly ash, blast furnace slag and silica fume on expansion performance of the common concrete and compensating-shrinkage concrete was researched. To the common concrete, adding fly ash or blast furnace slag can decrease the shrinkage rate, but adding silica fume deteriorate the shrinkage rate. To compensating-shrinkage concrete, mineral materials added cause its expansion rate decrease. Furthermore, the reasons of crack generating from the point of material and structure are analysis. The shrinkage characteristics of HSC and normal concrete at short term and long term are researched. Based on the above research, high performance expansive C50-C80 concrete, which posses good expansive properties, excellent flow ability, low slump loss and hydration heat.In order to improve the anti-cracking of some important projects, such as Cutting Wall, the workability and bulk stability of fiber-reinforced micro expensive concrete are researched. At last, this kind of material with high anti-cracking property is applied to actual project and the effect is exciting. We find that crackingcontrol is a synthetically project. The project design condition, produce, transport, pouring and curing, all of them are very important to the project quality. Because construction and curing quality is more important to anti-cracking performance of HSC and fatal to the compensating-shrinkage concrete than anything else, we should pay attention to them. So we think that anti-cracking of HSC should be designed according to project sorts. At last, we apply our achievement to actual project and get good effects.