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. The problem of rapid loss of workability of high strength concrete (HSC) must be resolved to facilitate the insitu use of HSC. This paper presents the effectiveness of an admixture, carrier fluidifying agent (CFA), in retaining the workability of HSC and the mechanical properties of the resulting concrete. The results showed that the workability of HSC mixes incorporating CFA can be maintained for a period of up to two hours. Laboratory trials using repeated dosing of superplasticizer were also carried out. Unlike the presently adopted repeated dosing method, incorporating CFA will not impose manpower, quality control and cost penalty as well as the risk of over-dosing of superplasticizer. Although the setting times were marginally extended and there was a slight air entrainment, the mechanical strength of HSC incorporating CFA showed no reduction comparing to that of the control. Keywords: High strength concrete (HSC), Carrier fluidifying agent (CFA), Workability retention, Repeated dosing. Dr Sammy Y.N.Chan is the Leader of the Concrete Technology Group at the Department of Civil and Structural Engineering of the Hong Kong Polytechnic University. His main research interests include high strength concrete, workability retention and concrete admixtures. Professor N.Q.Feng is the Director of Research Laboratory of Building Materials at the Tsinghua University. He is a member of the RILEM TC 78MCA Committee. His research interests include high performance concrete, concrete admixtures and a variety of construction materials. Mr Matthew K.C.Tsang is a PhD research student at the Hong Kong Polytechnic University. The theme of his research is the study of HSC incorporating CFA.
