ABSTRACT
Radical Concrete Technology. Edited by R K Dhir and P C Hewlett. Published in 1996 by E & FN Spon, 2-6 Boundary Row, London SE1 8HN, UK. ISBN 0 419 21480 1. ABSTRACT. This paper examines the characteristics of the shear-fatigue behaviour of ultra-high strength reinforced concrete beams. The mix proportion for the concrete was determined from a series of trial mixes using different cement contents and silica fume replacement levels. A constant W/(C+SF) ratio was used throughout, and the Powercon100 superplasticizer was added. The mix type with more cement and silica fume contents results in higher compressive strength and was used to produce the tested beams. Shear reinforcement ratios of 0, 50 and 100% according to the ACI 318-89 code were chosen for the study. Both static flexural tests and fatigue tests were carried out. The shear failure mode of the ultra-high strength concrete beams was found to be similar to that of the normal RC beams, except that brittle characteristics had been clearly shown. The results also indicated that the ultimate shear strength value of the ultra-high strength reinforced concrete beam was about twice the value calculated from the formula of ACI 318-89 code. A repair method with epoxy injection to the flexural and the diagonal tensile cracks was also investigated. No further propagation of the flexural cracks in the repaired specimens was found when reloading. Keywords: Ordinary Portland cement, Silica fume, Superplasticizer, Ultra-high strength concrete, Shear reinforcements, Ultimate shear strength, Fatigue strength, Flexural cracks, Diagonal tensile cracks, Epoxy injection. Professor & Dr Kae-Hwan Kwak is a Professor in the Department of Civil Engineering, WonKwang University. Ki-Woong Jang is a PhD Candidate in the Department of Civil Engineering, WonKwang University. Kyung-Hern Kwak and Won-Tae Kim are graduate students in the Department of Civil Engineering, WonKwang University.
