Reducing Cracking in Concrete Structures by Using Internal Curing with High Volumes of Fly Ash

Abstract

High volume fly ash (HVFA) concretes have been used in the past; however HVFA has been primarily advocated for use in mass construction applications. Recent interest in developing more sustainable construction materials has led to an increased interest in utilizing these HVFA mixtures in transportation structures such as pavements and bridges. These mixtures have a reduced carbon footprint, in addition to other improvements in the material performance. This paper presents a study utilizing the dual ring test to assess the benefits of the HVFA mortar mixtures with respect to reducing early age cracking. Three mortar mixtures were prepared with a water-to-cement ratio of 0.30. The first mixture is a plain cement mortar, the second mixture is a mortar where 40 % of the cement (by volume) was replaced with C class fly ash, and the third mixture is a mortar where 40 % of the cement (by volume) was replaced with C class fly ash and prewetted lightweight aggregate (LWA) to provide internal curing (IC). The cracking potential due to thermal and autogenous shrinkage was assessed. Results show a lower risk of shrinkage cracking in the HVFA mixture with internal curing. The IC mixture made using HVFA is more robust for construction at early ages.