Eco-durability index of self-compacting concrete incorporating high volume fly ash

Abstract

Designing concrete meeting the principles of sustainability becomes urgent in the construction of buildings and other civil engineering infrastructures. Sustainability of concrete can be assessed by considering its environmental, economic and social impact. Each impact may cover multi-criteria and parameters for the assessment. In this respect, the designers require practical tools so as to select the best alternative concrete mix design fulfilling the multi-criteria. This paper proposed an eco-durability index (EDI) as such tool for assessing the balance performance in term of environmental impacts and durability of self-compacting concrete (SCC) incorporating high volume fly ash. The fly ash content is in the range of 50%-70% of replacement level i.e. a fraction of cement replaced by weight of fly ash. The parameters adopted for assessing the environmental impacts (ecological index) are embodied primary natural resources depletion, embodied energy and embodied CO2; while the time to corrosion initiation period due to chloride ion ingress by diffusion mechanism is taken as durability parameter. The chloride ion diffusions of the concretes under study were determined following ASTM C1556 from the chloride profiles. The chloride profiles were obtained by salt ponding test according to AASHTO T259. The amount of chloride ion with respect to the depth of its penetration was determined by XRF method. Within the scope of this study, it is shown that an increase of fly ash will reduce the environmental impacts of SCC. However, the durability of concrete does not show a similar trend. Therefore, a balance performance considering the environmental impacts and durability is searched for by using the value of EDI. Based on the EDI, it is indicated that SCC with 70% fly ash replacement level gives the best alternative of SCC with respect to balance performance of environmental impacts and durability.