Issue 59

M. A. R. Elmahdy et alii, Frattura ed Integrità Strutturale, 59 (2022) 486-513; DOI: 10.3221/IGF-ESIS.59.32

SEM, EDS, TGA AND DTG RESULTS

Scanning electron microscope (SEM) EM test was used to examine mixes M6, M8, M12 and M13 compared with control mix M0. Both specimens of bacterial mortar and control mortar are checked using SEM to look for signs of microbial calcium carbonate precipitation, and the results are shown in Figs. 27:31. SEM test were carried out after 90 days of curing with the magnification of 1000X, 1500, 2000X, 2500X and 3000X. In comparison with the control mortar, the SEM results of the tested bacterial specimens showed fewer voids. Control mix specimens had many voids compared with bacterial mixes specimens, Also, bacterial specimens are denser in micro structures compared with control mix, this signifies that it improves the mortar's strength. It was observed that calcium carbonate and calcite crystals are formed by bacteria, leading to filling pores, while in control specimens were not observed significantly. Also, as the content of bacteria increases, the calcium carbonate content and calcite crystals increase, causing pores to fill. Calcium silicate hydrate (C-S-H) and ettringite as a result of cement hydration were also observed. The SEM analysis confirms the existence of calcite as well as higher levels of C-S-H in microbial mortars. These depositions in the pores increased the packing density of cement mortar, which improved its physicochemical and mechanical properties [33,43,50]. S

Figure 27: SEM images (1000X) after 90 days of curing for mixes (A) M0, (B) M12, (C) M13, (D) M8 and (E) M6.

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