Light weight concrete blocks have an important role in the last years for it is practical and economical benefit in the building construction. An It has light density providing high thermal insulation and less dead load normally all light weight concrete has fire resistance in its nature, as well as, these type of light weight block has the ability to support quite large amount of load and relatively easy to work and can be cut and shaped with hand tools.
The effect of high temperature on light weight concrete blocks was studied after exposure to (150,350,550)ºC for one hour. The effect of the method of cooling after heating (by air or water) on the compressive and flexural strengths were studied and compared together. The water absorption capacity was also measured during the process of water cooling. The compressive strength relatively increased with high temperature and air cooling , and also increased with measuring the exposed time up to (90) minute, above this time the compressive strength decreased. For water cooling the compressive strength trend to decrease . Flexural strength is decreased as the exposed temperature increased in all cases.
Key words: Concrete ,Light Weight Concrete, High Temperature.