Construction Joints in Normal and High Strength Concrete

This report describes the test rig used, and the results obtained, in a large investigation concerning the shear strength of construction joints in concrete. The work is centered on concretes in the strength range 20 to 100 MPa.

for this range of concrete strengths, smooth and rough construction joints have been studied.

It was found that the relative shear strength of a construction join is depending on the strength of the concrete, and that the relative shear strength is decreasing for increasing concrete strength.

It was also found that the Danish national code DS 411 generally predicts too low shear strength of construction joints. Based partly on the result obtained in this investigation, and partly on other test results, a revision of the code is proposed.

The investigation also points at the need for reevaluation of the classification rules for construction joints. This because high-pressure water or water/sand blasting of the construction does not seem to ensure that construction joint can be classified as a rough joint, although the roughness criteria as specified in the code is respected.