Influences of Silica Fume to Engineering Properties of High Volume Fly Ash Concrete (HVFC)

Abstract

High volume fly ash concrete (HVFC) is one kind of the most promising concrete materials in the 21^st century. HVFC has special properties such as high flowability, mechanical strength meets the requirements of contruction standards, low permeability, high durability, and others. Furthermore, HVFC is able to continuously develop strength during long time because the high activity alumina-silicates in the fly ash particles are dissolved slowly and prolong. Therefore, this study used fly ash (FA) and mineral additive of silica fume (SF) to replace a part of cement in concrete mixtures. The experimental results shown that FA can be completely used to replace up to 60% of cement (PC40) to fabricate HVFC. In addition, FA used in combination with SF to partially replace cement improved the workability of the HVFC fresh concret mixtures. The use of 60% FA to replace cement should be combined with 5 to 10% SF to produce HVFC with the highest compressive strength of 76.2 MPa after 90 days of curing. The morphologies and microstructure of HVFC product was characterized using SEM (scanning electron microscope) with evidences on dissolution and reaction of FA spherical particles to form the structures in HVFC matrix. This also explained for increase the strength of the concrete even if its mixture contains high FA. More significantly, this contributes an importance to the development and application HVFC in the construction industry in Vietnam. In addition, it is also good solution and great technical, economic and environmental significance that contributing to the goal of sustainable construction development not only in Vietnam but also all over the world.