Influence On Performance Of Concrete Mixed With Ultra-fine Limestone Powder

Fly ash resource is short and expensive in Wuhan, witch has seriously restricted the development of concrete industry, increased the cost of concrete. In most regions of our country, the resources of limestone is very abundant, Wuhan has plenty of limestone resource. The limestone can be made into limestone powder by the means of grinding, witch can solve this problem.This paper is based on the performance analysis of limestone itself, To study the influence of mixing limestone powder on the workability and mechanical properties of concrete when the specific surface area, amount and MB value of limestone powder is different and the influence of the mechanics performance and durability of concrete, when limestone powder is mixing with fly ash and granulated blast furnace slag.Researcher reaches the following conclusions.1、With the surface area of limestone powder increasing the circularity of limestone powder is getting better and better, the proportion of particles which are less than 10 μm is growing more and more, the fluidity ratio of cement mortar mixed with limestone is decreasing, setting time is shortened.The 7d、28d activity index of limestone powder was greater than 60%, witch meet the requirements of the specification.2、The change of MB value has the most severe effects on the workability of concrete. As the MB value of limestone powder gets bigger the initial value of the slump of concrete mixture gets smaller, the value of slump loss gets bigger.3、The higher the surface area of limestone powder is, the higher the strength of concrete.When the amount of limestone powder is 20% the value of compressive strength of concrete at 7d and 28d reaches the maximum.Continue to increase the amount of limestone powder, the compressive strength of concrete will be reduced.4、Compared to the reference group of concrete, the compressive strength of concrete at 7d is increased by 16%, compressive strength of concrete at 28d can also reach the standard set of compressive strength of concrete at 28d of 87.7%, when limestone powder completely replace fly ash.When replaced slag powder with limestone powder, the compressive strength of concrete at 7d and 28d will be reduced.5、The chloride resisting properties of concrete and carbonation resistance of concrete mixed with limestone powder is worse than the reference group of concrete. The chloride resisting properties of concrete and carbonation resistance of concrete of limestone powder replacing fly ash is better than that limestone powder replacing glass powder.