Abstract
The utilization of by-products and waste materials to substitute for the natural or manufactured resources is considered as a practical way to obtain green building materials. In concrete mixtures, amongst the many available options, Fly Ash (FA) as a by-product pozzolan has been used as a partial replacement of cement. As for the aggregates, lightweight agro-waste oil palm shell (OPS) can be used as a replacement to conventional aggregate for the production of lightweight aggregate concrete. The present communication aims to investigate the impact of FA on time-dependent development properties of OPS lightweight aggregate concrete, including density, water absorption, compressive strength up to 120-days, and drying shrinkage up to the age of 365-days under standard moist curing, partially early curing, and non-curing conditions. Additionally, drying shrinkage crack development was investigated. In this study, two series of concrete mixtures with different substitution levels of OPS (0%, 50%, and 100%) and FA were tested. From the obtained results, it was concluded that the incorporation of fly ash in OPS concrete reduces the density and compressive strength values. Dually, the initial and final water absorption values plus the rate of drying shrinkage at early and long-term ages increased. On top of that, a high potential of drying shrinkage crack, especially for mixtures with 100% OPS, was identified.
Highlights
The first use of lightweight aggregate concrete dates back to 1918 [1,2]
They reported that incorporation of Fly Ash (FA) of more than 10% resulted in a stiff mixture with low workability and difficulties for compaction, which caused a remarkable reduction in compressive strength
The reduction in compressive strength could be due to the absence of moisture during the curing period, which inhibits the pozzolanic reaction by FA
Summary
The first use of lightweight aggregate concrete dates back to 1918 [1,2]. Since its applications have become increasingly frequent and have spread throughout the world. There are different methods for the production of LWC but the common way is the utilization of lightweight aggregates (LWA), a generic name for the aggregates’ group, with a relatively lower density than normal-weight aggregates. 1120 kg/m3 (70 lb/ft3 ) are considered as lightweight aggregates [7] They can be used as a partial or whole substitution of normal-weight coarse or fine aggregates in concrete mixtures. Maghfouri et al [25] performed an experiment to investigate the optimum required OPS content in concrete concerning density, water absorption, mechanical properties, and drying shrinkage at both short-term and long-term ages. It was reported that OPS content in concrete mixtures shall be limited up to a maximum of 60% of the total volume of coarse aggregate; otherwise, a high rate of time-dependent properties such as drying shrinkage would impact the integrity and durability of such concrete. Study is evaluation of the time-dependent properties under different curing regimes
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