Title: Effect of Hot Weather Conditions on the Microcracking and Corrosion Cracking Potential of Reinforced Concrete

Author(s): Rasheeduzzafar and S. M. A. Al-Kurdi

Publication: Symposium Paper

Volume: 139

Issue:

Appears on pages(s): 1-20

Keywords: corrosion; cracking (fracturing); cyclic heat; velocity; strains; hot weather construction; microcracking; permeability; reinforced concrete; temperature; tensile strength; thermal expansion; water-cement ratio; Materials Research

DOI: 10.14359/3891

Date: 9/1/1993

Abstract:
Focuses on the damaging implications of the daily temperature fluctuations in the aggressive climatic conditions of hot-arid regions due to strain incompatibility resulting from widely differing coefficients of thermal expansion of the local crushed limestone aggregate and the hardened cement paste. The data strongly indicate that temperature fluctuations cause microcracking in concrete, which increase its permeability and lower its tensile strength and cracking time. In this investigation, concrete specimens with water-cement ratios of 0.40, 0.50, and 0.65, with cement content of 550 lb/yd 3 were subjected to cyclic heating in programmed ovens which carried out 120 temperature fluctuations, each simulating the temperature regime of a typical summer day in eastern Saudi Arabia. The thermal regime was characterized by a temperature swing from 27 to 60 C within a 24 hr period. This included the effect of concrete surface heating by direct solar radiation. Pulse velocity, permeability, and time-to-cracking data were developed in reference to cyclic heat-treated specimens at 20, 40, 60, 80, and 120 heating cycles. The cyclic heat-treated specimens had a significantly reduced pulse velocity, a noticeably increased permeability, and, depending on water-cement ratio, a 55 to 70 percent reduction in cracking time due to reinforcing bar corrosion. This implies that a significant degree of microcracking is induced in concrete due to the thermal incompatibility of concrete components.