Effect of high temperature on strength and mass loss of admixtured concretes

Chemical admixtures are used in concretes to prove some properties at ambient temperature. The admixtured concretes may present different behaviour at high temperature than at normal conditions. In this study, five different types of chemical admixtures - Superplasticizers (SP), hardening accelerators (HA), setting retarders (SR), air entrainers (AE) and water repellents (WR) - Were incorporated with different fraction of cement mass (0.5, 1.0, 1.5 and 2.0%), to investigate their influences on the strength and mass losses of concretes under high temperature. This study concerns the behaviour of admixtured concretes at ambient temperature 20 °C (normal conditions) and those subjected to temperatures 105 °C (oven dry) and 300 °C with a rate of 2 °C/min. Compressive-strength and mass loss tests were performed on the samples 10 × 10 × 10 cm3which were cooled up slowly to ambient temperature. It was concluded that among the chemical admixtures used, the superplasticizer (SP) significantly increased the workability of SPC. The tests results indicated that at a temperature of 300° C, the concrete with an air entrainer admixture caused the greatest loss of strength and mass when compared with others admixtured concretes. The lowest losses are those obtained for concretes with superplasticizers at this temperature.