Sulphate reduction in waste concrete aggregate Using bacillus subtilis

Abdul aziz, Nurhanim and Mohamed jamil, Putri anis syahira and Yusoff, Mohd zarir and Ismail, Norli (2024) Sulphate reduction in waste concrete aggregate Using bacillus subtilis. Journal of Sustainability Science and Management, 19 (4). pp. 10-27. ISSN 2672-7226

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Abstract

Waste concrete aggregate (WCA) can be re-utilised as a recycled material as it applies to numerous functions. High sulphate content in attached cement mortar was identified as a weakness of recycled material due to the developed expansion of delayed ettringite formation (DEF). The DEF results in micro-crack formation, which affects the compressive strength. The main objective of the present study was to treat WCA by Bacillus subtilis before being reused in recycled concrete mortar (RCM) production. The DEF of WCA was identified using X-ray diffractometric (XRD) techniques and soluble sulphate tests. The efficiency of B. subtilis in treating WCA was evaluated based on sulphate reduction on three variable factors, i.e., B. subtilis concentration, B. subtilis: WCA ratio, and retention time. Treated WCA (TWCA) from the WCA treatment by B. subtilis was reused as a part of RCM production. The compressive strength of RC was subsequently evaluated to determine its durability. Results revealed that WCA was rich in ettringite and contained 0.53% sulphate. The sulphate content in WCA was successfully reduced to 81.5% by B. subtilis when B. subtilis concentration was at 0.2 x 108 CFU mL1 , the B. subtilis: WCA ratio was 1:1 and the retention time was increased up to the 4th day. The construction of RCM using TWCA can potentially replace the natural concrete aggregate due to its higher compressive strength (26 MPa) compared to control (20 MPa). The study indicated that B. subtilis efficiently reduced sulphate in WCA to avoid microcrack formation on the RC surface.

Item Type:	Article
Uncontrolled Keywords:	Bacillus subtilis, waste concrete aggregate, delayed ettringite formation, sulphate reduction, comprehensive strength. Abbreviations: Waste concrete aggregate (WCA), delayed ettringite formation (DEF), interfacial transition zone (ITZ), extracellular polymeric substance (EPS), recycled cement mortar (RCM), treated waste concrete aggregate (TWCA).
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Divisions:	Faculty of Technology Management and Business > FPTP
Depositing User:	Mr. Mohamad Zulkhibri Rahmad
Date Deposited:	05 May 2025 06:42
Last Modified:	05 May 2025 06:43
URI:	http://eprints.uthm.edu.my/id/eprint/12522

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