Research On The Thickness Of Microbial Concrete Crack Repair Layer And Its Influenc

With the help of microbial induced carbonate precipitation that concrete with micro-cracks can realize self-healing has become a reaserch hotpot in recent years.At present,the width of crack repair has basically met the engineering requirements,However,the Repair layer thickness is not enough.And Repair layer thickness is an important index to evaluate the quality of crack repair.The paper provides a ba sis for improving the thickness of the repair layer by studying the influencing facto rs of self repair.,and made a detailed study on the efficiency of carrier、fly ash a nd₂on the crack Repair layer thickness,and on this basis,we studied the eff ect of Repair layer thickness on concrete performance,and the main work is as fol lows:（1）The growth and reproduction of microorganisms in different media and ure ase activity were studied.The results showed that when the p H value of the mediu m was greater than 11,the Microbial growth arrest.With the increase of calcium i on concentration,the activity of microbial urease decreased gradually.When the cal cium ion concentration was 2.5 mol/l,urease activity could not be detected.When t he urea concentration exceeds 2mol/l,the urease activity will not increase as the ur ea concentration continues to increase.（2）The factors affecting the Repair layer thickness are studied.The effects of ceramsite,recycled concrete and sisal fiber on the Repair layer thickness were com pared.As a microbial carrier,ceramsite had the highest Repair layer thickness of 145μm,which was 16%higher than that of the group directly mixed with spore sol ution.Using fly ash to replace part of cement,the results show that fly ash can ef fectively improve the yield of mineralization and precipitation,when the fly ash cont ent was 20%,t Repair layer thicknes was 152μm As an"endogenous"oxygen source for Bacillus metabolism,it was found that the Repair layer thickness reached 156μm when the dosage was 1%of the cementing material.（3）The influence of Repair layer thickness on the performance of concrete was investigated.The results indicate that the rate of impermeability repair increases dramatically as the Repair layer thickness increases.The impermeability repair rate is32.3%when the crack repair depth is 168μm;The recovery rate of compressive strength increased by 1.6 percentage points compared to the control group;When the thickness of the repair layer is 137μm,the compressive strength increases by 0.07MPa,compared to the control group.