SA Affordable Housing March / April 2018 // Issue: 69 - Page 18

FEATURES Preventing costly repairs Spalling of joints in concrete floors should be regarded as early warning of more serious potential long-term damage. By The Concrete Institute | Photos by The Concrete Institute Pictured above and below: Examples of spalled concrete floors. S palling is the peeling, popping out or flaking of a concrete surface. Moisture and often salt too, pushes outward from the inside. The size and cost of spalling repairs can be reduced if the damage is detected and repaired at an early stage. On any construction site, whether a single storey stand-alone unit or multi-storey project – from the civils work onwards – concrete forms the basis for many components. Concrete’s quality and stability can speak directly to the safety of the users or occupants – from foundations to heavy traffic areas and from slabs to stairways. It is therefore important to ensure proper identification of any concrete that may be compromised. Although concrete is already a technical subject, basic knowledge, such as best practice for repairs, can assist in long- term effects that would otherwise create unnecessary risk. Spalling of joints is the cracking, breaking or chipping in the immediate vicinity of joints, usually within 100mm of the joint. A spall usually does not extend vertically through the slab but extends to intersect the joint at an angle. Spalling at joints usually results from: • Excessive stress at the joint caused by accumulation of incompressible material in the joint and subsequent expansion of adjoining slabs in concrete pavements; • Weak concrete at the joint; • Poorly designed or constructed load-transfer devices or failure of such devices; and • Poorly constructed joints. Early repair of spalling is needed to improve serviceability, deter further deterioration and provide proper edges so that the joints can be resealed effectively. Before any repairs are carried out, it should be determined if the spalling is due to a loss of load transfer at the joints. If this is the case, the load transfer needs to be restored before edge spalls are repaired. Reinstating load transfer generally requires full-depth, partial panel repair or reconstruction of the joint. Although concrete is already a technical subject, basic knowledge, such as best practice for repairs, can assist in long-term effects that would otherwise create unnecessary risk. See more on page 18. 16 MARCH - APRIL 2018 AFFORDABLE SA HOUSING