Bio-mineralized self-healing recycled aggregate concrete for sustainable infrastructure

Rao Arsalan Khushnood; Zarar Ali Qureshi; Nafeesa Shaheen; Sikandar Ali

doi:10.1016/j.scitotenv.2019.135007

Bio-mineralized self-healing recycled aggregate concrete for sustainable infrastructure

Sci Total Environ. 2020 Feb 10:703:135007. doi: 10.1016/j.scitotenv.2019.135007. Epub 2019 Nov 7.

Authors

Rao Arsalan Khushnood¹, Zarar Ali Qureshi², Nafeesa Shaheen², Sikandar Ali²

Affiliations

¹ Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Corso Ducadegli Abruzzi 24, Turin 10129, Italy; NUST Institute of Civil Engineering (NICE), School of Civil and Environmental Engineering(SCEE), National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan. Electronic address: rao.khushnood@polito.it.
² NUST Institute of Civil Engineering (NICE), School of Civil and Environmental Engineering(SCEE), National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan.

PMID: 31744694
DOI: 10.1016/j.scitotenv.2019.135007

Abstract

Various carriers have been investigated by researchers to introduce bacteria inside the concrete however, factors such as local availability, cost and long-term protection of bacterial cells have barred the application of this contemporary technology in the construction industry. In the present study, bacteria were immobilized via recycled coarse aggregate (RCA) and virgin fine aggregate (FA) besides direct induction to preserve natural resources and emulate sustainability. The application of RCA in substitution of virgin coarse aggregate is dropping anthropogenic emissions, minimizing energy consumption and managing construction waste effectively. Vegetative cells of Bacillus subtilis bacterium were incorporated in RCA through vacuum impregnation to boost crack healing efficiency. Crack healing efficiency was studied by quantifying the crack healing widths and percentage of strength regained after pre-cracking at 3,7 and 28 days. Similarly, mechanical properties were gauged via compressive and split tensile strengths at specified intervals while healing precipitate was characterized using analytical means. Results of experimental work revealed that specimens having RCA and 50% virgin FA as bacteria immobilizers exhibited the most efficient crack healing remedy by healing crack widths up to 1.1 mm and recovering 85% of compressive strength. Specimens containing RCA exclusively displayed a maximum of 0.7 mm crack healing widths and 76% strength recovery while direct incorporation of bacteria lagged behind with 0.6 mm crack healing width having 69% strength recovery. Likewise, synergetic formulation and direct induction depicted increase in compressive strength of 4% and 6% respectively while exclusive RCA formulation decreased the compressive strength up to 3% Moreover, field-emission scanning electron microscopy (FE-SEM), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) and X-ray fluorescent (XRF) characterized the crack healing precipitate as bio-mineralized calcite crystals.

Keywords: Autonomous healing; Bacillus subtilis; Bio-mineralization; Crack healing; Recycled coarse aggregate; Sustainable concrete.

MeSH terms

Compressive Strength
Construction Materials*
Industrial Waste
Recycling*
Waste Management

Substances

Industrial Waste