Investigation of strength, frost-resistance and impermeability of concrete construction joints

Abstract

1. The strength of connection of concrete with construction joints and interval between concreting up to 8 h decreases up to 12%, in the case with no special treatment of the joint surface. The strength of connection of concrete with construction joints and interval between concreting of 16 h to 15 days decreases by 18 to 29% by comparison with strength of test pieces without joints, in the case with correct and careful treatment of joint surfaces. 2. For each type of cement one should carefully ascertain maximum allowable time between stages of concreting without formation of construction joints, that is, without treatment of the joint surface. 3. The frost-resistance of concrete with construction joints, if prepared by an accepted method, ensures adequate life-span for monolithicreinforced-concrete structures. 4. The composition of the clinker has no real effect on strength of connection of concrete joints, nor on frost-resistance (when tested up to 300 cycles), nor on impermeability. However, the presence in the cement of a large amount of gypsum (in the form of a semihydrate) causes rapid stiffening and less of workability of concrete mixes, and this makes for difficult concrete placing and may harm the structure of the concrete.