| Due to its brittleness and low tensile strength,cement-based composites in engineering structures will inevitably crack.The capsule self-healing system provides a feasible method for cement-based composites to crack and delay the potential damage.However,the internal organic microcapsules currently studied have poor compatibility with the matrix,so it is a hotspot to select a material that can have good compatibility with cement-based materials.Light aggregate usually has good adhesion and compatibility with cement base material,and light aggregate has more internal pores,which can achieve a similar effect with the core material of microcapsule adsorption repair agent.Its compatibility with cement-based material is better than that of organic microcapsule and base material.In this paper,the self-repair performance of the system in cement-based materials was studied by encapsulating lightweight aggregate ceramsite adsorbed sodium silicate solution as the built-in repair agent.Through the study of adsorption and lightweight aggregate ceramsite encapsulation technology to increase the rate of adsorption of lightweight aggregate,by testing the preparation of cement base material related to the change of the performance,especially the crack width,bibulous rate changes and strength recovery,to study and characterization under different curing healing encapsulation ceramsite cement base material built-in sodium silicate solution since the repair effect of repair system.Scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD)were used to analyze the microstructure and morphology of the self-repairing products.The phase characteristics of the self-repairing products at the crack section were preliminatively discussed,and the influence mechanism of the products on the self-repairing effect was analyzed.The main research contents and experimental conclusions are as follows:(1)Carry out the adsorption test of sodium silicate solution by ceramsite and the encapsulation treatment after adsorption.The best adsorption and encapsulation conditions were obtained by adsorption and encapsulation experiments,and the possibility of self-healing in cement-based materials was verified.In the adsorption treatment,the optimal combination of conditions: 40% concentration of sodium silicate solution,vacuum adsorption for 10 min,standing for 24 h,under this combination of ceramsite adsorption rate is 75.9%.Choose epoxy resin solution as the packaging treatment membrane solution,where epoxy resin: curing agent =2:1.(2)The self-healing effect of encapsulated ceramsite adsorbing sodium silicate solution on cement-based materials is related to the specimen curing environment.According to the decrease range of capillary water absorption rate,crack closure coefficient and stress recovery rate,the healing effect of outdoor environment is not as good as that in the curing room,and the healing effect of water environment is more favorable to healing(3)The incorporation of sodium silicate solution is beneficial to the repair of specimens.After 28 d of healing and curing in three kinds of curing environment,the crack repair effect of test group was better than that of control group,and the capillary water absorption rate of test group decreased by 70.9% and 35.53% respectively after28 d of healing and curing in water environment.The crack closure coefficient of experimental group was 100%,and that of control group was 69.12%.The stress value of test group was recovered to 64.23%,and that of control group was 29.61%.(4)Microstructure analysis of self-repair products.Scanning electron microscopy(SEM)was used to observe the morphology of the healing product at the crack section of the specimen,and it was found that the morphology of the repair product at the crack section of the specimen cured in the water environment was more abundant.After 28 days of water environment curing,the samples of the control group and the test group were selected at the same depth position at the crack section to conduct an energy dispersive spectroscopy(EDS)comparative analysis,and it was concluded that the Si element content at the crack section of the test group was more than that of the control group.Phase analysis of the repair products by X-ray diffraction(XRD)showed that the repair products of the test group and the control group after 28 days of water environment conservation were similar,but the test group released sodium silicate solution due to cracked ceramsites.More calcium silicate hydrate(C-S-H)gel was produced,which promoted the repair of cracks in the specimen. |
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