Investigation of concrete slab crack when placed directly on clay

In this study, investigation of concrete slab cracks when placed directly on clay, types of cracks in seam zone, cracks depth and width, modulus of elasticity and compressive strength were studied. Also the effects of the cracks on the physical properties of concrete due to dry shrinkage. A total of eight concrete mixtures were produced with 500 kg/m3 of total cementitious materials content and with a constant water/binder ratio of (0.55). each mixture were casted over clay layer, Each layer of clay had various water content ratio from 0% to liquid limit , concrete samples were either cured by spraying at 23℃ or maximum temperature of 28 days curing period. Test results revealed that 28-days compressive strength enhanced while leading to reduce in ultrasonic pulse velocity, it was found that the concrete mixtures that placed over high clay water content had higher compressive strength and lower dry shrinkage values compared to the samples that casted over low water content clay. However e-modulus of elasticity increased due to dry shrinkage.