基于生物矿化机理的自愈合混凝土制备与表征

研究旨在利用微生物诱导碳酸钙沉淀机理,研制新型细菌自愈合混凝土。在高pH条件下培养,筛选出一组与枯草芽孢杆菌相关的产芽孢杆菌。将筛选得到的耐碱枯草芽孢杆菌M9进行生物矿化沉淀测试,X射线衍射(XRD)和扫描电镜(SEM),结果表明沉淀矿物为呈方解石形态的碳酸钙。以枯草芽孢杆菌M9为修复剂,掺入聚乙烯醇(PVA)纤维制备自愈合混凝土梁试件。利用引气剂在水泥净浆混合料中产生微孔,为微生物提供生态位。对养护14 d的混凝土梁试件进行三点弯曲试验,获得宽度约为0.3 mm的裂纹。28 d后,细菌代谢等作用形成碳酸钙晶体填充物自动填充微裂纹空隙。后续SEM测试表明:方解石是裂纹填充矿物主要形态,且晶体表面残留部分细菌印记。愈合后的混凝土梁在第二次弯曲测试下的抗弯强度提高了约14%,该强度恢复是通过修复基体裂纹和纤维-基体界面的粘结力来实现的。

Preparation and characterization of self-healing concrete based on biomineralization mechanism

The purpose of this study is to develop a new type of self-healing concrete by using the mechanism of microbial-induced calcium carbonate precipitation.A group of Bacillus subtilis are screened and cultured in high pH solution.The selected alkali resistant Bacillus subtilis M9 is subjected to biomineralization precipitation test.The results of X-ray diffraction(XRD)and scanning electron microscopy(SEM)test show that the precipitated mineral is calcium carbonate in calcite phase.Using Bacillus subtilis M9 as repair agent,self-healing concrete beam specimens are prepared by adding polyvinyl alcohol(PVA)fiber.The micro pores are produced in the cement paste mixture by air-entraining agent,providing ecological niche for microbe.Three point bending tests are carried out on the specimens of concrete beams cured for 14 days to obtain cracks with a width of about 0.3 mm.After 28 days,the calcium carbonate filler formed by bacterial metabolism automatically fills the microcracks.The follow-up SEM tests show that calcite is the main form of crack filling minerals,and some bacterial imprints remains on the crystal surface.At the same time,the flexural strength of the healed concrete beam is increased by about 14%under the second bending test,which is achieved by repairing the matrix cracks and the bond strength of the fiber matrix interface.