Study On Deposition Regularities Of Calcium Carbonate In Microbial Grouting

As one of the most widely used construction materials in the world,concrete material is easy to crack under load due to its low tensile strength.The appearance of cracks will not only cause leakage of underground structures,but also affect the safety of structures.The technology of microbial induced calcium carbonate can effectively repair concrete cracks and improve impermeability.In this paper,through experimental research,the calcium carbonate deposition law of microfiber grouting repairing cracks under different influencing factors was discussed to provide theoretical support for plugging of underground structures..Nine groups of parallel grouting tests for concrete split cracks under the action of self-weight were designed.The test parameters include different amounts of bacteria inoculation?2 times,6 times,and 12 times the volume of the bacterial solution in the crack volume?,whether the bottom pasted bacteria liquid filtered layer?medical cotton?at the bottom of the crack,whether the crack is poured into bacterial fixation liquid before grouting.After each round of grouting is completed,a group of test blocks are kept for water seepage test to characterize the plugging effect of the cracks;at the same time,the test blocks are cut open to observe the thickness of the calcium carbonate deposition on the inner wall of the cracks;the calcium carbonate is weighed;Using the electron microscope's own image processing software to calibrate the crack,parameters such as crack width and calcium carbonate formation thickness can be obtained.After multiple rounds of grouting,all test blocks are blocked,and the test ends.The main conclusions of the test are as follows:the number of rounds of bacterial liquid cracks that are filled with 2 times,6 times,and 12 times the crack volume of each round is completely blocked 10 times,6 times,and 4 times.The fewer the number of bacteria-filling cycles required for crack plugging,the higher the efficiency of repairing the cracks.The fixation effect of the f fixation fluid pre-filled control group is better than that of the non-fixation fluid control group.Adding the fixation fluid before pouring the bacterial solution can improve the efficiency of crack repair and the amount of CaCO₃ generated in the crack,making CaCO₃ more easily adhere to the inner wall of the crack.More uniform distribution,thereby improving the utilization of bacteria liquid.A comparison group with a bacterial liquid filter layer is set at the bottom.The critical plugging position is at the bottom of the crack.For a comparison group without a filter layer,the critical plugging position is at the middle and lower part of the crack.As the number of grouting cycles increases and the vertical depth of the cracks increases,the thickness of the CaCO₃ layer on the inner wall of the cracks also increases.At the same time,the rough inner wall of the cracks,large vertical inclination and roundabouts make CaCO₃ easier to deposit.