Preliminary Study On High Strength Concrete With Fire Insulation

High Strength Concrete (HSC) is widely used in super-tall building structures and large span structures. Explosive spalling is always observed in HSC in the high temperature because of its high density of the microscopic structure. Spalling is adversely to the security under fire of HSC. The use of polypropylene (pp) fibers in HSC could prevent the spalling completely. But the residual strength and anti-chloride ion penetration performance of this kind HSC are significantly decline after high temperature. Generally speaking it can not satisfy the requirements of daily situations. How can we find a good way that not only can resist the spalling at high temperature but also can keep the correlated performance of HSC after high temperature. Further researches should be carried out.The ideal of this study is: (a) Some HSC specimens with fire insulation were tested at elevated temperatures, and the effective thickness of fire insulation that can resist explosive spalling of HSC is got. (b) On the basis of that the influence of thickness of fire insulation on the chloride ion permeability of HSC after high temperature is discussed. Finally the optimal thickness is proposed. (c) The computer program for the analysis of structures under ambient and elevated temperature conditions (SAFIR) used for analyzing the fire resistances of high strength concrete columns with fire insulation. It also gives practical fire resistance calculating formulae of this kind column through plenty of calculation.The mainly context of the dissertation is as follows:1.Four groups of HSC specimens with fire insulation were tested at elevated temperatures, and the influence of thickness of fire insulation on the explosive spalling of HSC is discussed. Comparison with recently methods, the advantages and disadvantages of this research are given. At last the preliminary thickness of fire insulation that can resist spalling is got.2. The chloride ion permeability of HSC with fire insulation after high temperature was tested with RCM and the influence of thickness of fire insulation is researched. Combining durability and explosive spalling resistance, we suggested the optimal thickness of fire insulation on the surface of HSC.3. The computer program for the analysis of structures under ambient and elevated temperature conditions (SAFIR) used for analyzing the fire resistances of high strength concrete columns with fire insulation, and the influence of different axial loading ratios, cross-section dimensions, reinforcement ratios and load eccentricity ratios are discussed. It also gives practical fire resistance calculating formulae of this kind column through plenty of calculation.