Mohammed Abughali, Hilal EL-Hassan, Tamer El-Maaddawy, Mouaz Chkhachirou
Abstract: The purpose of this study is to investigate the workability and the compressive strength of geopolymer concrete incorporating recycled concrete aggregates (RCA) and glass fibers (GF) with varying aspect ratios. The binder material was a combination of class F fly ash and ground granulated blast furnace slag at a ratio of 1:3. Actually, dune sand served as fine aggregates. The coarse aggregates used were either natural aggregates or RCA. Unlike hydrated cement, geopolymers are activated in an alkaline solution. Therefore, a combination of sodium silicate and sodium hydroxide initiated the proper geopolymerization process. In fact, this particular solution creates a conducive environment for the exothermic chemical reaction to produce the newly formed concrete mixtures. Through this study, the impact of multiple parameters such as, the replacement percentage of natural aggregates with RCA, binder content, amount of additional water (added only to the alkaline activator solution), particle size distribution of RCA, and volume fraction of glass fibers were studied in detail. Experimental results revealed that the RCA-geopolymer concrete mixture exhibited a reduction in compressive strength by approximately 25%, compared to its NA-based counterpart geopolymer concrete, while the workability was unaffected. Meanwhile, increasing the binder content from 300 to 450 kg/m3 in RCA-based geopolymer concrete led to an improvement of 56 and 7% in the 7-day compressive strength and workability, respectively. Adding up to 100 kg/m3 of water increased the workability up to 240 mm while decreasing the compressive strength by almost 10%, compared to its counterpart concrete made with 50 kg/m3 of water. Moreover, when RCA was sieved to exclude particles smaller than 4.75 mm and larger than 19 mm, the slump increased to 210 mm. This process also led to a 29% increase in 1-day compressive strength and a 35% increase in 7-day compressive strength. The addition of glass fibers had a significant negative impact on the workability of geopolymer concrete as it led to a decrease in the workability by 2 and 9% when the volume fraction was 1 and 2%, respectively. The experimental findings emphasize the potential of using RCA as a substitute for natural aggregates in slag-fly ash blended geopolymer concrete reinforced with glass fibers, without compromising performance.
Keywords: Geopolymer concrete, Glass fibers, Recycled concrete aggregates, Workability, Compressive strength.
Date Published: August 13, 2024 DOI: 10.11159/ijci.2024.013
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