Strength efficiency of metakaolin in concrete
K. Ganesh Babu, Indian Institute of Technology, Chennai, India
P. Dinakar, Indian Institute of Technology, Chennai, India
The use of mineral admixtures is widely accepted, because of several improvements possible in concrete composites and the overall economy. Of these metakaolin is one mineral admixture that appears to have significant potential for the production of high-strength and high-performance concretes. Although available information on metakaolin concretes is limited, the present paper attempts to quantify the 28-day cementitious efficiency of metakaolin in concrete at various replacement levels from the data available in the literature. It was seen that the efficiency of metakaolin in concretes can also be defined through a procedure adopted earlier for other cementitious materials like fly ash, silica fume and ground granulated blast-furnace slag (GGBS). The overall strength efficiency was found to be a combination of two parameters, one depending on the age and the other depending on the percentage of replacement, as is the case with other pozzolans.
Bond clause proposals for FRP bars/rods in concrete based on CEB/FIP Model Code 90. Part 1: Design bond stress for FRP reinforcing bars
R. Tepfers, Chalmers University of Technology, Göteborg, Sweden
The bond clauses in the CEB/FIP Model Code 1990 (MC90) were written for steel reinforcement in concrete. Since then, fibre reinforced polymer (FRP) reinforcing bars have been introduced as an alternative. Reinforcing steel is a homogeneous material; FRP reinforcements, however, are made of a combination of different materials with various shapes. All these FRPs perform differently under different conditions. For example, in severe environments, where steel is not durable, FRPs may perform well. To make use of fibre composites, it is necessary to bring these materials into codes of practice and the easiest way is to adapt the code clauses for steel reinforced concrete to FRP reinforced concrete. The clauses should include boxed values open for individual coefficients of different FRPs. The necessary coefficients for the code models should be determined using systems of appropriate and coupled test methods. This paper covers a code proposal for the design bond stress. Proposals for the design lengths and tension stiffening code clauses will be presented separately.