Abstract
As silica fume has the properties such as pozzolanic reaction, micro-filler effect and ball-bearing effect like fly ash, it is very useful to improve the consistensy and strength development of concrete.However, the concrete mixed with silica fume needs a chemical admixture such as the superplasticizer because it shows a low consistency with the content of silica fume.
In the absence of a chemical admixture, it was shown that the optimum mixing percentage of silica fume is about 5%judging from the consistency and compressive strength of mortar.To get the more economical mixing percentage of silica fume, an air entraining agent was used to the mortar mixed with silica fume.It was found that this agent can improve the consisitency of mortar mixed with silica fume but has the defect reducing the compressive strength to a large extent.
Nextly we used the superplasticizer to improve the consistency, the strength development of mortar and concrete mixed with silica fume.In the case of mortar it was shown that the 1.2% superplasticizer gives the maximum mixing percentage of silica fume 30%without reducing the compressive strength.Then, the density, pulse velocity, dynamic modulus of elasticity and compressive strength of concrete mixed with 30%silica fume and 1.2%superplasticizer were measured. As a result, the superplasticizer greatly improved the consistency and the compressive strength of concrete especially after the age of 28 days.
