ABSTRACT
The water/cement ratio has a considerable effect on the strength of concrete, and on the amount of shrinkage. The elastic modulus varies according to the concrete strength; and changes with time due to creep, depending on the intensity of applied stress. The amount of creep depends also on the age of the concrete when it is first stressed. Further, the strength of concrete depends on the nature of the aggregates - their particle shape, surface texture and grading - and whether the concrete is cured in air or water, and at what temperatures. And stresses arise merely from the effects of shrinkage, and from temperature changes in restrained structures, without the application of any useful external loading: and variation of moisture content and temperature gradients across the thickness of a structural unit can cause considerable bending stresses.
