Heat Treatment of Fine-Grained Cementless Concrete Based on High-Calcium Fly Ash and Slag from Thermal Power Plants

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Title: Heat Treatment of Fine-Grained Cementless Concrete Based on High-Calcium Fly Ash and Slag from Thermal Power Plants

Author(s): S. I. Pavlenko

Publication: Special Publication

Volume: 153

Issue:

Appears on pages(s): 497-512

Keywords: curing; durability; fly ash; heating; moist curing; slags; thermal gradient; Materials Research

Date: 6/1/1995

Abstract:
Cementless fine-grained concrete based on high-calcium fly ash and slag from thermal power plants was developed by the Siberian Metallurgical Institute in 1990. This paper presents the results of a study of schedules of heat treatment of the cementless concrete aimed at improvement of quality and durability of concrete. Prior to heat treatment, concrete was cured for three, six, and 12 hours at 60, 80, and 100 C. The temperature rise and cooling took three hours each. This cycle was provided by an automatic steam-curing chamber. After moist curing at high temperature using the above cycle, the specimens were tested for compressive strength immediately after cooling to room temperature and at the age of 28 days. It was found that the temperature of the isothermal heating should be in the range of 80 to 100 C. The best results were obtained with 100 C, although it is difficult to achieve this temperature, especially in cast-in-place construction. It also demands a great amount of electrical energy. Therefore, 80 to 90 C should be acceptable as the optimum temperature range. The optimum time of the isothermal heating is 9 to 12 hours. However, the computer processing of the results of the investigation showed that the optimum time of curing was six to seven hours. The technology and recommendations for heating of cementless slag ash concrete, by means of heating wires used in the construction of low-rise houses both in summer and winter periods, have been developed.