ABSTRACT

This study presents the results of the investigation of the effects of elevated temperature on the compressive strength of grade 40 concrete. A total of 16 cubes specimen were cast, cured at ambient temperature in the laboratory and subjected to various temperature regimes before testing. A mixture of 1:2:3 regimes (cement: fine aggregate: coarse aggregates) with water content ratio of 0.44. fine aggregate lying in zone 2 ofthe sieve tests as well as granite ofmaximum size of 12.5mm was designed for the investigation using the department of environment method. Specimens cured f or 28days were subjected to unaxial compressive loading test at room and elevated temperature of 400, 600, 700 and 800 degree Celsius at 45 minutes duration. Surface concrete cracking is a visible type of damage that has significantly adverse effects on the mechanical properties and durability properties of concrete. This paper also presents an experimental study on the identification and quantification ofsurface cracking of concrete heated to different temperatures ranging from 400 to 800°C. In addition to the quantification of the residual compressive strengths of concrete after high temperature exposure, both initial surface absorption and total porosity were measured. The crack density was determined using a flat bed scanner and then images were treated using paint shop pro program. The mechanical properties of concrete were largely affected by temperatures beyond 400°C and were very feeble when temperatures exceeded 700°C. The surface cracks' density, initial surface absorption and total porosity by boiling methods gave a rapid indication on concrete durability.