Innovative Test Technique to Evaluate “Self-Sealing” of Concrete

Abstract

Abstract Concrete is prone to cracking when subjected to tensile forces because of its low tensile strength. The cracking potential is an even bigger concern when concrete is relatively young and is in the plastic stage. Cracks induced early can grow with time because of drying shrinkage and with application of service loads. Concrete, which is otherwise impermeable, allows for free passage of moisture and other deleterious chemicals when it is cracked, leading to reduced durability of the material and, in many cases, reduced service life of the structure. The severity of some of these issues can be alleviated because of an inherent property of concrete known as “self-sealing.” As the name suggests, “self-sealing” allows for the cracks (of limited width) to be sealed on their own over a period of time. However, currently there is no standard test technique to quantify this property of concrete and other cement-based materials, such as mortar. An innovative and straightforward technique was developed by the authors and is presented in this paper. In this technique, a standard crack is induced in concrete cylinders using a standard crack-inducing jig (SCIJ). The specimens are then inserted in special rubber sleeves and this assembly is then subjected to a constant water head. The reduction in flow through the cracked specimen is measured at a given time to compare the performance of different specimens. This technique can also be used to compare the performance of concrete mixes modified using various admixtures. This paper describes this innovative test technique and includes sample test results to explain the analysis process proposed by the authors.