The values of (fb/fc) range from 16.75% to 23.50% for concrete made of marble dust as cement replacement, whereas these values range from 17.27% to 21.89% for concrete made of marble dust as sand replacement respectively. Moreover; it can be noticed that the values of ratio between steel–concrete bond strength and concrete compressive strength for 0.40 w/p ratio are smaller than those of concrete with 0.50 w/p ratio. This trend may be due to the reduction in w/p ratio where the compressive strength is positively more influenced by the reduction of w/p ratio than bond strength.
5.4. Ultrasonic pulse velocity (UPV)
Ultrasonic pulse velocity test results with the usage of marble dust as a partial replacement of cement and sand at 28 days of curing are given in Table 4. From this table, the use of marble dust either as a cement replacement or a sand replacement has insignificant effect on the value of the ultrasonic pulse velocity. This slight variance is because the ultrasonic pulse velocity proportional with the fourth root of concrete compressive strength [14].