After the concrete is poured, hydration of the cement continues and, after some time, excess water is lost. During these stages, the physical behav­ iour of concrete can be roughly divided into two sections:

• changes that can take place before setting of the concrete has commenced, namely sedimentation, bleeding and plastic shrinkage and

• changes which take place after the concrete has started to set, namely thermal cracking, drying shrinkage, creep and fatigue.