Utilization and selection of proper fly ash in cost effective green HTPP-ECC design

Abstract

The inherent requirement of high cement content in Strain Hardening Cementitious Composite (SHCC) causes increase in cost high environmental pollution and unsustainability problems. There is a growing trend to use fly ashes as mineral admixture in matrix phases of composites to solve these problems. In this study special types of environmentally friendly SHCCs known as High Tenacity PolypropyleneEngineered Cementitious Composites (HTPP-ECC) have been prepared by using two distinct type of fly ashes (FA) (Class C and Class F). Detailed micro-structural characterizations of these fly ashes have been performed before composite preparation. The effects of fly ash type fly ash/cement (FA/C) ratio and water/cement (W/C) ratio on fresh and hardened properties of HTPP-ECCs have been investigated by using different matrix combinations. The flexural performances of these composites have been compared under four-point loading conditions. In addition to flexural properties multiple cracking potential of composites were compared by counting the average crack number and residual crack widths at unloaded condition. A fiber distribution analysis has also been performed by using Scanning Electron Microscopy (SEM) for each composite and associated with the flexural performances. Finally CO2 emissions and costs of composites have been compared by considering a conventional concrete mix design (C25/30) and frequently used PVA-ECCs in the literature. Results showed that physical and chemical properties of fly ash directly affects the performance of composites both in fresh and hardened state and F type fly ash was found more advantageous in producing HTPP-ECC compared to C type fly ash employed in this study. Cost effective green HTPP-ECCs having flexural strengths up to 11.5 MPa and deflection capacity between 8.5 and 11.5 mm can be obtained by a proper design. (C) 2017 Elsevier Ltd. All rights reserved.