الفهرس 
CHAPTER (1) ”INTRODUCTION”Only 14 pages are availabe for public view
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Abstract
Calcium carbonate precipitation resulting from microorganism’s metabolism is a novel approach for self-healing concrete cracks.This process is called microbiologically induced calcite precipitation (MICP) or biomineralization. It can heal the micro cracks autonomously, improve concrete properties, and decrease the costs of maintenance and repair. Bacterial concrete, or self-healing concrete, is a concrete made by incorporating bacteria and nutrients in the mixture to precipitate calcite on the bacterial cell surfaces and within the pores. This natural technique is an environmentally friendly and a sustainable method.
This work investigates the effect of incorporating of alkaliphilic bacteria and different calcium sources on the physical and mechanical properties of concrete and mortar. The characterization was confirmed by using SEM and XRD spectra analysis. Two types of ureolytic bacteria; Bacillus Pasteurii DSM 33 with a concentration 1x109 CFU/mL and Bacillus megaterium with cell density of 2× CFU/mL was used for the experiments. Three different bacterial nutrients were added to the mixes; calcium lactate, calcium formate, and calcium acetate. There were six groups of the work; the first group was conducted by using Bacillus pasteurii that was added to cement paste
mixes with two ratios of (0.5% and 0.25% of cement weight). Calcium lactate, calcium formate, and calcium acetate were added as nutritions to bacteria by two ratios of 0.25% and 0.125% of cement weight. Setting time test was performed to investigate the effects of bacteria and different nutrients on setting time of cement paste. The second group was conducted by using Bacillus pasteurii that was added to cement paste mixes
with two ratios of (0.5% and 0.25% of cement weight). Calcium lactate, calcium
formate, and calcium acetate were added as nutritions to bacteria by two ratios of 0.25% and 0.125% of cement weight. The third group was conducted by using Bacillus pasteurii. It was added to concrete mixes with two ratios of (0.5% and 0.25% of cement weight). Calcium lactate was added as nutrition to bacteria by two ratios of 0.25% and
0.125% of cement weight. Superplasticizer was used in concrete mixes with 1% of cement. The fourth group was performed by using Bacillus pasteurii. It was incorporated into mortar with one ratio of (0.25% of cement weight). Calcium lactate,
calcium formate and calcium acetate were added as nutritions to bacteria by a ratio of 0.125% of cement weight. The fifth group was conducted by using Bacillus megaterium. It was added to concrete mixes with two ratios of (0.5% and 0.25% of cement weight). Calcium lactate, calcium formate, and calcium acetate were added as nutritions to bacteria by two ratios of 0.25% and 0.125% of cement weight. The sixth
group was conducted by using Bacillus megaterium. It was added to concrete mixes with two ratios of (0.5% and 0.25% of cement weight). Calcium lactate was added as nutrition to bacteria by two ratios of 0.25% and 0.125% of cement weight. Superplasticizer was used in concrete mixtures with 1% of cement. For the second, the third, the fourth, the fifth, and the sixth groups, rate of water absorption test, coefficient
of water absorption test, compressive strength test, and flexural strength test were performed at the age of 7, 28, 90, and 120 days. Also, XRD and SEM/ EDX analysis were performed. Tests results of the bacterial samples were compared with the results of the control samples. It was noticed that inclusion of Bacillus pasteurii decreased initial setting time and increased final setting time of cement paste mixes. Inclusion of
bacteria and different used bacterial nutrients revealed varied decrease in rate of water absorption for concrete and mortar mixes. A significant increase in the compressive strength and flexural strength for concrete and mortar mixes compared to control mixes. Among all mixes, Bacillus pasteurii 0.5% with acetate nutrition (BPA0.5)concrete mix achieved the least reduction in rate of water absorption and coefficient of
water absorption at all ages. It also had maximum increase in compressive strength and flexural strength at all ages. It had rate of water absorption value 40.62% of that value of control concrete mixture at age of 120 days. Compressive strength and flexural strength values of Bacillus pasteurii 0.5% with acetate nutrition (BPA0.5) increased by45.3% and 27.65%, respectively when compared with those values of control concrete specimens at age of 120 days. Calcium lactate with superplasticizer mixes achieved rate of water absorption values less than those values of calcium lactate without superplasticizer mixes. Bacillus pasteurii 0.5% with lactate nutrition and superplasticizer (BPSP0.5) had rate of water absorption value 78.94% of that value of Bacillus pasteurii 0.5% with lactate nutrition mixture (BPCL0.5) at age of 120 days. Mortar mix Bacillus pasteurii 0.25% with formate nutrition (MF) had the least water absorption and its value was 61.76% of that value of control mortar specimens at age of
120 days. Mortar mix Bacillus pasteurii 0.25% with acetate nutrition (MA) had
maximum increment in flexural strength at all ages and its value was 115.7% of that value of control mortar specimen at age of 120 days. Among all mixes of the fifth and the sixth groups, Bacillus megaterium 0.5% with acetate nutrition concrete mix (BMCA0.5) had a maximum increase in compressive strength at all ages and its value was 134.9% of that value of the control concrete specimens at age of 120 days. Bacillus megaterium 0.5% with lactate nutrition concrete mix (BMCL0.5) achieved the highest flexural strength value at all ages and its value was 145% of that value of control
concrete specimens at age of 120 days. Enhancement of properties was due to calcite deposition on the bacteria cell surfaces and within the pores. The X-ray spectroscopy analysis and SEM imaging indicated the formation of calcite crystals in bacterial concrete and bacterial mortar specimens which made them denser with less voids than the control specimens. from the above results using of bacteria is recommended
because the mineral precipitation which occurs as a natural process and is an
environmental friendly method.