Discussion. Causes of Movement in Reinforced Concrete Turbo-Blocks and Developments in Turbo-Block Design and Construction.

Abstract

wrote that since the initiation of the work described in the Paper more information on the rate at which concrete dried had been obtained at the Central Electricity Research Laboratories, Leatherhead. Moisture gauges, similar to those mentioned, had been placed in two large concrete structures, one being the biological shield at a nuclear power station, the other a 6 ft dia., 7 ft block of concrete in the laboratory. Readings from these gauges had been taken for over 5 years at ambient temperatures and for 13 years at higher temperatures. Fig. 12 gave a plot of the moisture gradients obtained and this indicated that, even after 5 years, the depth to which significant drying expressed as loss of evaporable water had occurred was not greater than 2 ft. These results were obtained from the difference between an active gauge and a sealed control gauge kept under the same temperature conditions for the same period. It had been found that the sealed gauges indicated an apparent moisture loss of about t% per year (expressed as the dry weight of the gauge). Quite possibly the dryingout referred to in § 44 was this 'loss' and the actual reduction in the moisture content of the concrete was much less. Fig. 12 were under ambient temperature conditions (16" k4"C). If the temperature was increased, the rate of drying increased considerably. Fig. 13 showed the effect on the moisture loss 3 in. from the surface of 5 year old concrete when the temperature was raised from an average of 20°C to an average of 36°C. Dr B. Mayfield (Civil Engineering Department, University of Nottingham) suggested that from 5 95 et seq., it would appear that the future of concrete turbo-blocks was in the balance and that one of the principal reasons for this move away from the Appendix stated that low-tuned concrete blocks 'would involve an unusual degree of use of concrete was because of the 'uncertainty as to the value of E (dynamic)'. The concrete quality control and the most accurate determination of elastic constants '. 107. The results shown in