Thermal properties of commercially available high-strength concretes

This paper summarizes the thermal properties of commercially available high-strength concretes. Five concretes with anticipated compressive strengths in the range of 10 000 to 20 000 psi (69 to 138 MPa) were tested. W/C ratios ranged from 0.26 to 0.43; water-to-total cementitious material ratios ranged from 0.22 to 0.32. The concretes, containing either no mineral admixtures, silica fume only, or both fly ash and silica fume, were delivered by a ready-mix supplier for laboratory testing. Tests covered by this paper include thermal conductivity, thermal diffusivity, specific heat, and drying rates. Thermal conductivity was measured using a guarded hot plate (ASTM C 177) at 85, 300, and 700 degrees F (30, 150, and 370 degrees C). Thermal conductivity was also measured using the hot-wire method (ASTM C 1113) at 701 300, 570, 540, 1110, 1380, and 1830 degrees F (25, 150, 300, 450, 600, 750, and 1000 degrees C). Thermal diffusivity was measured, using the guarded hot plate apparatus, at 95, 250, and 500 degrees F (35, 120, and 250 degrees C). Thermal diffusivity was also measured using a dynamic radial heat flow method continuously From 210 to 1830 degrees F (100 to 1000 degrees C). Thermal properties at high temperatures differed depending on the method used. Specific heat was measured on saturated concrete at ambient temperatures, Rates of drying for initially moist cured specimens were determined by oven-drying thermal conductivity specimens at 150, 185, and 220 degrees F (65, 85, and 105 degrees C) prior to thermal testing. Mass loss was measured at temperatures up to 1740 degrees F 950 degrees C) at heating rates of 4, 36, and 90 degrees F (2, 20, and 50 degrees C) per minute.