Strength retrieval and microstructural characterization of Bacillus <italic>subtilis</italic> and Bacillus <italic>megaterium</italic> incorporated plain and reinforced concrete: Fid-Bau Portal

Strength retrieval and microstructural characterization of Bacillus subtilis and Bacillus megaterium incorporated plain and reinforced concrete

Ul Islam, Shahid / Waseem, Shakeel Ahmad

Abstract

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Highlights • Pre-cracked BSRC and BMRC beams showed 38% and 41.8% flexural strength recovery, respectively. • BSRC and BMRC beams exhibited 62.54% and 63.32% crack depth recovery, respectively. • 38.82% and 39.43% lower water absorption in BSPC and BMPC specimens than control concrete. • Rietveld research showed that bacterium-incorporated concrete sample had more calcite than those without bacteria.

Abstract This study aims to develop a self-healing concrete by using Bacillus subtilis and Bacillus megaterium as self-healing agents and subsequently extend the application to structural elements. Bacillus subtilis and Bacillus megaterium were directly incorporated in concrete at 0.5%, 1.0%, and 1.5% by weight of cement. Compression test, flexural strength test, and split tensile test were performed to analyse the strength properties of self-healing concrete. The self-healing efficiency of plain concrete was determined in terms of regain in compressive strength by testing standard pre-cracked concrete cube specimens, while as for reinforced concrete beams, self-healing efficiency was determined by means of repeated four-point load test (4PLT) and non-destructive testing (NDT). In addition to regain in compressive strength of plain concrete specimens, a significant recovery in flexural strength and crack depth was observed in both the Bacillus subtilis incorporated reinforced concrete (BSRC) beam and Bacillus subtilis incorporated reinforced concrete (BMRC) beams after 56-days of curing. The effect of Bacillus subtilis and Bacillus megaterium on water absorption capacity of concrete was studied and a significant reduction in water absorption capacity was observed. Microstructural analysis in the form of X-Ray Diffraction and Field Emission-Scanning Electron Microscopy analysis was also conducted on concrete samples. The microstructural analysis confirms the calcite precipitation by bacteria in cracks which attributes to the strength retrieval of cracked concrete specimens.