Although the mortar, grout or fine concrete is in a highly confined state under predominantly plane stress conditions and should achieve compressive strength higher than fcd, a low design strength is normally used because the edges of the bedding tend to spall off. This lead to a non-uniform stress distribution. Another factor which leads to a reduction of the joint strength is when there is a great difference in the elastic response between the bedded material and the precast concrete which may result in localised contraction, lateral tensile stress and splitting forces. This effect may become important when the joint thickness is greater than 50 mm.