Effect of mortar spacers of different grades on the performance of concrete

Abstract

Rebar spacers are crucial component in reinforced concrete structures. Their purpose is to provide and maintain cover for the reinforcement bars. Since rebar spacers are permanent part of the member their quality must be taken into consideration, failure to do so will jeopardize the durability of the whole reinforced concrete member. In this research project, the effect of mortar spacers on the durability and strength of concrete is investigated by examining the penetration of moisture and other corrosive agents such as chloride through the mortar spacer or through the concrete-spacer interface, assuming that the concrete is in good condition dense and durable. For lab experimentation, cube and prism specimens with different curing ages and conditioning were cast, the specimens were embedded with mortar rebar spacers and tested in terms of strength and durability. Strength tests have been conducted such as compressive strength and flexural, also durability tests for cube specimens were conducted including water absorption, expansion and shrinkage, chloride penetration and carbonation. Results showed that the presence of rebar spacer in concrete increases the ingression and transporting of moisture and other corrosive agents, especially at the concrete-spacer interface and when the quality of the spacer is lower compared to the quality of the concrete. Moreover, the spacer will negatively affect the flexural strength of prism specimens by initiating cracks. The spacers might seem small and hold low value during construction, but because they are permeant part of the structure and they are placed every =1 m along the rebars, their overall effect on ingress of corrosive agents might be significant, and that must be considered by the concrete designers and practitioners.