Issue 59

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

E FFECT OF BACTERIA CONTENT %

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sing bacteria BM, the best bacteria content when compared to control mix M0 is 2.5% in mix M6, with an increase of 56.6% and 71.7% at 28 and 56 days, respectively. Using bacteria EMCC, the best bacteria content when compared to control mix M0 is 2.5% in mix M8, with an increase of 38.6% and 54.2% at 28 and 56 days, respectively. The amount of CaCO 3 precipitated in the mortar has a positive effect on its flexural strength [45,47,49]. On the other hand, when comparing bacteria FP to control mix M0, 5% in mix M14 was the best content, with increases of 68% and 108.5% at 28 and 56 days, respectively. The increase in strength using FP bacteria confirms the fact that crystals are precipitated by the bacteria in mortar matrix and calcium carbonate stands out as reported by other researchers [3,34,42].

Figure 23: Effect of bacteria type on mortar bending strength for specimens without pre-cracking, at 7 days, 28 days, 56 days, and 90 days: (A) using 2×10 8 concentration of bacteria BM, (B) using 2×10 9 concentration of bacteria BM, (C) using 2×10 8 concentration of bacteria EMCC, (D) using 2×10 9 concentration of bacteria EMCC and (E) using bacteria FP.

E FFECT OF BACTERIA CONCENTRATION

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he bending strength values increase as the bacteria concentration rises to 2×10 9 CFU/ml. Using 0.25% bacteria BM, for example, the difference between mixes M1 and M2 is 3.95 MPa at 28 days and 3.61 MPa at 56 days. Utilizing 0.25% bacteria EMCC, the difference between mixes M3 and M4 after 28 days is 1.53 MPa and 2.71 MPa

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