Concrete is the most widely used construction material in the world. When constructing large concrete structures, concrete may have to be placed in multiple lifts. In these cases, fresh concrete is placed on hardened concrete. The interface that is formed between these two lifts of concrete is known as a construction joint. Construction joints are common in reinforced concrete systems. However, little is known on how construction practices, specifically the preparation and curing of these joints, affects their strength and durability.
State Highway Agencies (SHAs) require special treatment of these construction joints. The Washington State Department of Transportation (WSDOT) requires that construction joints be water cured for 7 to 10 days prior to placing the next lift of concrete and that the construction joints be saturated for a minimum of 4 hours before placing the fresh concrete. WSDOT also requires that water from the curing and wetting of the construction joints be collected, tested, and treated before release. This often requires the construction of a complex drainage and water treatment system, which is expensive. These requirements were implemented with the objective of ensuring that the joint achieves sufficient strength and will resist deterioration throughout the life of the structure. However, very little research has been performed to assess whether these requirements lead to higher joint strength and better joint durability. Hence, the factors that influence these construction joints need to be identified and quantified through research.
An experimental investigation was performed to evaluate concrete construction joints prepared with various surface characteristics and curing conditions. Three curing conditions (no cure, water cure, and compound cure) and three surface conditions (as-finished, intentionally roughened, and sand blasted) were evaluated. Forty-five slant shear specimens and twenty-seven durability specimens were designed, constructed, and tested to evaluate the bond strength and durability of construction joints, respectively. Durability is defined here as the rate of chloride penetration through the construction joint.