Study On Optimization And Performance Of Multicomponent Composite Self-healing Materials

The concrete crack self-healing technology is a new method of repairing cracks in concrete proposed by scholars at home and abroad.The technique is to initiate and repair micro cracks in concrete itself by releasing or generating new materials.At present,the technology of concrete fracture self-healing includes shape memory alloy,polymer solidification,osmotic crystallization and microorganism self-healing.Although these methods can be used to repair cracks actively to some extent,many problems still exist in practice.In this paper,calcium salt,SAP,organic acid and parent materials were selected according to the theory of slow release expansion,internal maintenance and osmotic crystallization and the repair effect of these components on the micro-cracks in cement mortar were studied to determine their most appropriate proportion.The mechanism of fracture repair was analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Finally the effects of composite self-healing materials on the cracks self-healing and crack resistance of concrete were discussed by adding selected components.Based on the above studies,the main conclusions are as follows.(1)Using stearic acid sodium as coating material and calcium salt as repair components,respectively,the self-healing effect of coated and uncoated calcium salt components on the crack in cement mortar is studied by comparatively testing ultrasonic properties,crack width and crack depth.Compared with the control specimens,the self-healing ability of the late fracture(prefabricated cracks at the age of 28d)can be improved by adding calcium salt and uncoated calcium salt components.The repair effect of coated calcium salt components is better than that of uncoated one,and when its component content is 6%,the crack repairing effects are the best.In addition,it is found that water curing condition is more favorable to self-healing of cracks than dry and wet cycle one.(2)Using SAP as the internal curing component and calcium salt group as repair components,the self-healing effect of SAP and calcium salt mixture on cement mortars were studied by comparatively testing ultrasonic properties,crack width and crack depth.Compared with the control specimens,the self-healing ability of the late fracture(prefabricated cracks at the age of 28d)can be improved greatly by adding the mixture of both SAP and calcium salt components either coated or uncoated.The repair effect of SAP and coated calcium salt components is better than that of SAP and uncoated one,and when SAP is 6% and coated calcium salt components is 6%,the crack repairing effects are the best.(3)Using organic acid salt(sodium gluconate/sodium citrate complex)and parent material(FM-SN cement-based permeable crystallization type water proof material)as penetration crystalline materials,respectively,the self-healing effects of those components on the micro-cracks in cement mortar have been studied by comparatively testing ultrasonic property,cracks width and depth.Compared with the control specimens,both the organic acid salt and parent material can improve the crack self-healing capability on the late cracks(prefabricated cracks at the age of 28d),and the repairing effects of organic acid salt components is better than that of parent material,when organic acid salt is 0.1%,the crack repairing effects are the best.In addition,it is also found that water curing condition is more favorable to self-healing of cracks than dry and wet cycle one.(4)Two groups of composite self-healing materials,coated calcium salt-SAP-organate and coated calcium salt-SAP-parent material,were prepared in this section.The self-healing effects and anti-cracking ability of the above composite materials on the micro-cracks in concrete have been studied by comparatively testing ultrasonic property,cracks width and depth.Compared with control specimens,the addition of the two composite self-healing materials not only improves the compressive strength of concrete to a certain extent,the self-healing capability of late crack(Prefabricated cracks at the age of28d),but also enhances the early crack resistance of concrete,and the repairing effects of organic acid salt components is better than that of parent material.