How To Control Unsightly Wall Cracks
Verical wall cracks can be minimized by installing contraction joints to control the loaction of cracks or reinforcing the width of cracks. Concrete volume changes due to changes in moisture and temperature. As concrete dries, it shrinks. Length change related to drying shrinkage for unreinforced concrete can range up to .08% whereas normal reinfroced concrete is about 0.02% to 0.03% due to the internal restraint associated with the reinforcing. For an unreinforced or lightly reinforced 100 ft. wall, drying shrinkage to shorten teh wall up to abaout one inch. If the wall is normally reinforced, shortening is reduced to about 1/4 to 3/8 of an inch. With regards to thermal contraction, our 100 ft. wall subjected to a 50 farenheight temperature drop tries to shorten an additional 5/8 of an inch. Wall shortening from concrete drying shrinkage and/or thermal cooling combined with restraints including wall corners, intersecting walls and foundations with dowel bars causes vertical cracks to from. Due to shrinkage and restraints that resist wall shortening, tensile stresses form and when stresses exceed the tensile capacity of the concrete, cracking occurs.
