Study On The Properties Of High Performance Concrete With Compound Mineral Admixtures

This paper is a study about admixtures compounding with grinding steel slag powder, fly ash and silica fume, instead of cement partly, making into concrete, to take the strength, durability and micro analysis of concrete with compounding admixtures as the main research contents on experiment. We study some of the properties about concrete, such as compressive strength, splitting tensile strength, anti-chloride ion penetration, carbonation, freezing-thawing resisting cycle properties, dry-shrinkage , micro pore structure and so on, then compare properties of concrete with compound mineral admixtures to that of the common concrete. We can get the main conclusions as followed:(1) It has been studied that relations between the strength of concrete and the replacement quantity, the ratio of admixtures, water-binder ratio and slag fineness, the result of experiment demonstrates that the strongest effect factor is replacement quantity, suggest to control 20%~40% in scope, water-binder ratio is the second one, the best ratio is 0.35.(2) By the anti-chloride ion penetration test, it shows that compound three kinds of mineral admixture can obviously improve the anti-chloride ion penetration performance of concrete, the best replacement ratio is 40%~60% in scope.(3) By carbonation test, it is clear that the anti- carbonation performance of the common concrete is better than the compound admixtures, the more the substitution, the more the carbonation depth.(4) By freezing-thawing resisting cycle test, it shows that compound admixtures can significantly enhance the ability of freezing-thawing resisting cycle, the best replacement ratio is 20%.(5) By dry-shrinkage test, it is clear that with the addition of substitution, concrete shrinkage strain decreases at first and then increases, the best replacement ratio is 40%.(6) By the mercury test, it shows that the pore structure of concrete mixed with silica fume and steel slag powder, mixed with silica fume,steel slag powder and fly ash is better than that of common concrete. That is to say, using compound admixtures can effectively improve the microstructure of concrete, and super-compound effect is especially prominent.