Heat loss compensation in semi-adiabatic curing test of concrete

Abstract

To alleviate early thermal cracking of concrete, a maximum limit is often imposed on the adiabatic temperature rise, which has to be measured by an adiabatic curing test using a specially designed curing chamber. In practice, for convenience and simplicity, the curing tests conducted on site are not truly adiabatic and thus should be regarded as semi-adiabatic. In a semi-adiabatic curing test, due to heat loss, the measured temperature rise is lower than .the adiabatic temperature rise by an error dependent on the specimen size and the heat insulation provided. Herein, to minimize such error, a heat loss compensation method of estimating the heat loss from the spatial and time variations of the measured temperature and compensating for the heat loss, accordingly, is proposed. Ten laboratory-made concrete mixtures were tested to verify the applicability of the method. In addition, two batches of ready mixed concrete, each cast into 0.5 and 1.0 m (1.64 and 3.28 ft) cubes, were tested to demonstrate how a semi-adiabatic curing test could become independent of specimen size and much less affected by imperfect insulation after heat loss compensation. With the proposed heat loss compensation applied, the errors in the adiabatic temperature rise were all within ±1.3 °C (±2.3 °F). Copyright © 2008, American Concrete Institute. All rights reserved,.