Application of MgO Compound Expansion Agent in Concrete Filled Steel Tube

Abstract

An experimental investigation on the restrained expansion rate of motar, and a component test on the temperature and strain history of concrete filled steel tube (CFST) were carried out to evaluate the effect of calcium oxide (CaO) and magnesium oxide (MgO) compound expansion agent (EA) on the volme stability of CFST. The results indicated that CFST has experienced drastic temperature rise and drop process at its early age, but the hydration reaction activity of CaO expansion agent generally used at present was so high that they couldn’t compensate CFST thrinkage at temperature drop stage effectively. Light burned MgO clinker with active reaction time about 100 s and light burned CaO clinker were compounded in a certain ratio as a new kind of concrete expansion agent was applied in CFST and it matched the shrinkage history of CFST well, therefore, the expansion prepressing stress from core concrete to steel tube wall has been established and maintained effectively.