Investigation of compressive strength-color change relation of mortar exposed to high tempareture

ABSTRACT The physical and mechanical properties of reinforced concrete structures change if they are exposed to high temperatures. The changes in the properties of the reinforced concrete causes cracks and spalls which weakens the bonds between the bar and the concrete. Therefore, before deciding whether structures exposed to high temperatures should be repaired or demolished, their final state should be carefully examined. In previous studies, it has been observed that significant changes took place in the color of concrete just as the changes in the mechanical properties but no relationship has been established between the strength and the color change. In this study, the effects of temperature and cooling regimes on the physical and mechanical properties of the mortar were observed. The mortar production was made with siliceous and calcareous aggregates, Portland cement, silica fume, fly ash and slag. Mineral admixtures replaced 10 % cement by weight. These mortars were exposed to 100, 200, 300, 600, 900 and 1200 °C. Samples cooled to the room temperature in water and in air. Control tests were applied on these samples and Munsell Color System components hue, value and chroma were measured by digital spectro photometer. Test results showed similarities in the change of compressive strength and color of mortar which exposed to high temperature. A relationship is established between compressive strength and the color change of mortar. Two separate formulas are formed based on different types of aggregate. These formulas are expected to show us residual strength of the concrete and the temperature that it was exposed to, based on the color measurements taken from the concrete structure. Keywords: Color, compressive strength, high temperature, mortar, pozzolan. XI