Mechanical and durability performance of sustainable bacteria blended fly ash concrete: an experimental study

Figures & data

Table 1. Composition of Portland cement and fly ash used in this study.

	Percentage (%)
Constituents	Portland cement	Fly ash
SiO2	22.02	61.90%
Al2O3	4.71	27%
Fe2O3	2.76	7%
CaO	64.3	0.70%
MgO	1.00	0.60%
Na2O	0.14	0.93%
K2O	0.61	0.9

Table 2. Physical properties of materials used in concrete mixture.

Properties	Cement	Fly ash	Coarse aggregate	Fine aggregate
Sp.gravity	3.15	2.3	2.6	2.54
Fineness modulus	-	-	2.89	2.13
Water absorption (%)	-	-	1.08	0.066
LOI (%)	0.9	0.80	-	-

Table 3. Proportion of concrete constituents present in the mixes.

	Series	Cement (kg/m^3)	Replacement levels (%) FA	Fine aggregates (kg/m^3)	Coarse aggregate (kg/m^3)	W/C	Water (kg/m^3)	Bacterial dosage (cells/mL)
Amount of materials required for three 150 mm cube specimens	C	5.6	0	10.13	16.74	0.5	2.8	0
	CF1	5.04	0.56	10.13	16.74	0.5	2.8	0
	CF2	4.48	1.12	10.13	16.74	0.5	2.8	0
	CF3	3.92	1.68	10.13	16.74	0.5	2.8	0
	CB(3)	5.6	0	10.13	16.74	0.5	2.8	10^3
	CBF1(3)	5.04	0.56	10.13	16.74	0.5	2.8	10^3
	CBF2(3)	4.48	1.12	10.13	16.74	0.5	2.8	10^3
	CBF3(3)	3.92	1.68	10.13	16.74	0.5	2.8	10^3
	CB(5)	5.6	0	10.13	16.74	0.5	2.8	10^5
	CBF1(5)	5.04	0.56	10.13	16.74	0.5	2.8	10^5
	CBF2(5)	4.48	1.12	10.13	16.74	0.5	2.8	10^5
	CBF3(5)	3.92	1.68	10.13	16.74	0.5	2.8	10^5
	CB (7)	5.6	0	10.13	16.74	0.5	2.8	10^7
	CBF1(7)	5.04	0.56	10.13	16.74	0.5	2.8	10^7
	CBF2(7)	4.48	1.12	10.13	16.74	0.5	2.8	10^7
	CBF3(7)	3.92	1.68	10.13	16.74	0.5	2.8	10^7

Table 4. Test results for the growth of microbes at various pH with temperature as a parameter.

Bacteria	Temperature (°C)	Growth in buffer alkaline solution pH
		8	9	9.5	11	12
Bacillus Sphaericus	37	++	+++	+++	++	+

+ low growth, ++ average growth and +++ good growth.

Figure 1. Growth profile of B. sphaercius with variation in temperature.

Table 5. Results of compressive strength.

Specimen type	7 days (MPa)	28 days (MPa)	60 days (MPa)	90 days (MPa)
C	25.39	33.33	37.28	38.79
CF1	23.2	31.84	36.13	37.11
CF2	21.8	30.59	33.75	34.74
CF3	20.4	29.18	32.37	33.41
CB(3)	28.16	36.80	38.23	39.76
CBF1(3)	25.38	34.31	36.82	38.47
CBF2(3)	23.40	32.63	34.17	36.04
CBF3(3)	21.20	30.29	33.18	34.72
CB(5)	31.76	40.69	43.74	44.90
CB1(5)	27.80	37.40	41.47	43.47
CBF2(5)	26.20	35.18	39.80	42.10
CBF3(5)	24.20	32.21	37.60	40.80
CB (7)	29.18	39.37	37.54	40.97
CBF1(7)	26.95	35.49	36.18	39.30
CBF2(7)	24.10	31.73	33.21	35.67
CBF3(7)	22.43	32.79	32.19	34.71

Table 6. Ratio of compressive strength to split tensile strength.

Specimens	7 days	28 days	Bacteria concentration (cells/mL)
0% FA	8.41	8.69	10^5
10% FA	8.32	8.45	10^5
20%FA	8.66	9.00	10^5
30%FA	9.41	9.81	10^5

Table 7. Results of compressive strength.

Compressive strength (MPA)	Curing period (days)	Bacteria solution to water ratio (bacteria concentration, 10^5 cells/mL)
31.12	7	0.3
36.11	28	0.3
41.04	60	0.3
41.90	90	0.3
31.24	7	0.4
36.64	28	0.4
42.37	60	0.4
42.21	90	0.4
31.47	7	0.5
37.81	28	0.5
42.46	60	0.5
43.62	90	0.5
32.02	7	0.6
38.19	28	0.6
43.12	60	0.6
44.47	90	0.6

Table 8. Sorptivity values for of FA concrete with and without bacteria.

Sorptivity (mm/min^1/2)
	28 days		60 days
FA %	FA concrete	FA bacterial concrete (bacterial dosage 10^5cells/mL)	FA concrete	FA bacterial concrete (bacterial dosage 10^5cells/mL)
0	5.33	4.02	4.92	3.47
10	3.95	3.29	3.57	2.99
20	4.42	3.68	4.02	3.44
30	4.83	3.81	4.41	3.68

Figure 2. (a) Scanning electron micrographs of plain concrete. (b-–d)Scanning electron micrographs showing presence CaCO₃ produced image of BBFC.

Figure 3. XRD pattern of concrete samples at age of 28 days of curing: (a) plain concrete, (b) bacterial concrete (cell concentration 10³ cells/mL) and (c) bacterial concrete (cell concentration 10⁵ cells/mL).