Paper Title
Estimating of Compressive Strength of Different Types of Concrete by Nondestructive Tests

The objective of this research is to investigate the effect of the coarse aggregate content, type of coarse aggregate (normal weight and light weight), and amount of steel fiber in concrete on compressive strength, both rebound number and ultra-sonic pulse velocity. Moreover, the relationship between compressive strength and rebound number, ultrasonic pulse velocity (UPV) was discussed. The experimental work included testing of twenty-four mixes of concrete. The mixes were divided into two groups; each group consisted of twelve mixes, first group mixes consisted of normal weight coarse aggregate, second group mixes consisted of lightweight coarse aggregate, in each group, three contents of coarse aggregate and four percents of steel fiber (0, 0.25, 0.5, 0.75% of concrete volume) were used. It has been noticed that, the UPV increases with increasing coarse aggregate content in normal weight coarse aggregate concrete and vice versa in lightweight coarse aggregate concrete. The increment of age (from 7 to 28 days) leads to higher compressive strength, rebound number and UPV. The steel fiber content showed pronounced effect on the values of UPV. The results also show that, there is a good correlation between compressive strength and rebound number as well as UPV for the two types of concrete.