Effective heat-treatment regimes for large, hollow concrete blocks: Fid-Bau Portal

Effective heat-treatment regimes for large, hollow concrete blocks

Adamenkov, A. A. / Kudryashov, M. G. / Korenyako, N. F. / Novitskii, A. E. / Grishin, V. I.

Conclusions Based on analyses of experimental manufacturing, under shop conditions at the construction site, of large blocks with a cross sectional dimension up to 2.5×2.5 m and wall thickness from 0.5 to 0.8 m, we can recommend regimes with maximum temperatures of 40 and 60°C (Fig. 6).Heat treatment of precast concrete blocks intended for service in the fluctuating water level zone of a hydro-electric power station should be carried out by the low-temperature, regime. In other cases, it is recommended to use the medium-temperature regime.To reduce the time of heat treatment the concrete mix should be placed in a mold preheated to 40°C. In this case, the temperature of the concrete mix being placed should not be below 20°C.The temperature should be raised to the maximum of 60°C at a rate of not more than 10°C/h for a wall thickness of 0.5–0.8 m.The rate of cooling the concrete depends mainly on the thickness of the block and in each specific case should be established experimentally, when working out the regime under industrial conditions. We can recommend roughly the following rates of cooling depending of wall thickness of the hollow block: up to 0.5 m, 1.5°C/h and from 0.51 to 0.8 m, 1.0°C/h.The time of isothermal heating is determined from the condition of obtaining a concrete strength of 0.7 $ R_{28} $ by the end of heat treatment.