Concrete is a composite material, consisting, mainly, of three phases: coarse
aggregate, cement mortar, and the interface zone between them. The characteristics
of the interface zone largely govern the bond between cement paste or mortar and
aggregate. The restraining effect of aggregate to drying shrinkage strain depends
much on the bond between aggregate and cement paste.
In this paper, it is aimed to investigate the effect of coarse aggregate
characteristics, that affect bond strength, such as; type, shape, surface texture, and
moisture content, on drying shrinkage. Four types of coarse aggregate were used.
Three of them were normal-weight, while the fourth was a light-weight one. Each
type of coarse aggregate was used in two moisture conditions, dry and saturated.
The testing program extended to 150-days age and comprised; length change,
modulus of elasticity, compressive and splitting tensile strength of concrete.
It is concluded that using saturated coarse aggregate always yields higher
shrinkage strain than dry aggregate. The percentage increase seems to be affected
by the aggregate water absorption. At early ages, After 28 days, there is large
differences in relative shrinkage for different mixes. Later than 28 days, the
variation in ratios settled to approximately fixed values