Development of sustainable lightweight concrete using fly ash cenosphere and sintered fly ash aggregate

Abstract

The present research work explores the use of fly ash cenosphere (FAC) and sintered fly ash aggregate (SFA) as replacements of natural fine aggregate (NFA) and natural coarse aggregate (NCA), respectively, for development of sustainable structural lightweight concrete (LWC). Total sixteen concrete mixes have been prepared by replacing both NFA and NCA with FAC and SFA, respectively, having different combinations i.e. 0%, 50%, 75% and 100% each. The effects on the properties of the concrete mixes like workability, plastic and dry density, compressive, split tensile, flexural and bond strength, water absorption, volume of permeable pores, pulse velocity and rebound number, due to inclusion of FAC and SFA, are experimentally investigated and catalogued. Based on the content of FAC and SFA, the 28 days compressive, split tensile, flexural and bond strength are found to be within the range of 19.35–32.04 MPa, 1.83–3.48 MPa, 1.81–4.27 MPa and 6.95–8.33 MPa, respectively. The density of the above mixes ranges from 1226 kg/m3 to 2048 kg/m3. From this study, it is concluded that the structural LWC can be produced with the use of high volume of waste products, such as FAC and SFA, which minimize the waste disposal problems and preserves the natural resources. It is worth mentioning that out of fifteen concrete mixes with FAC and SFA considered here, all the mixes except two mixes, i.e. concrete mixes with 50% FAC only and 50% SFA only, satisfy the requirements of structural LWC as per ACI 213R-03. In spite of these advantages, the LWC mixes produced using SFA and FAC possess higher water absorption and volume of permeable pores as compared to the normal concrete, which shows the concern on the durability aspects of these LWC mixes. Hence, the durability properties of these concrete mixes are to be investigated in order to find their suitability in the construction. Moreover, the microstructural study needs to be carried out to support the trends of the mechanical properties of the concrete mixes using SFA and FAC observed in the present investigation.