4.STUDIES ON EXECUTION OF STEEL STRUCTURE ENCASED IN CRUSHED STONE AND LIGHT-WEIGHT AGGREGATE CONCRETE : Settling and bond characteristics of such concrete

Abstract

In this report the results of experimental studies are shown with respect to the settling of wet concrete with crushed stone and with respect to the bond between such concrete and steel bar. The results of the experiments are shown in the following: (1) Main factor governing the settling of wet concrete are its consolidating characteristic which may be represented by its unit weight and its water content which is most affected by water holding capacity of light-weight aggregate. The capacity depends on the shape of aggregate and the distribution of void space. (2) For the purpose of reducing the amount of settling of wet concrete, it may be effective to minimize the water content of concrete without changing the consistency by means of adding AE agent or fly-ash in the concrete. However, the quantity of fly-ash to be added as a substitute for cement should not exceed 15% of the weight of cement. (3) Since the settling of light-weight aggregate concrete is governed by water-holding capacity of aggregate, the amount of settling may be small if a certain kind of light-weight aggregate is used. (4) The settling of wet concrete causes unfavorable effect to the bond between concrete and horizontal bar. (5) Retamping of wet concrete is an effective measure to improve the bond between concrete and lower side of horizontal bar. It should be noted that inner revibration sometimes affects the bond unfavorably when the concrete is liable to settle. (6) The bonds along upper and lower side of horizontal bar and those along hoizontal and vertical bars have been compared, and the relationship between compressive strength of concrete and bond strength along holizontal and vertical bars have also been determined by means of a new method of measurement.