| The cracking of concrete,caused by the deformation or the load,is almost inevitable.The existence of cracks will greatly affect the safety and durability of concrete structures.Therefore,the self-healing technology of cracks in concrete has been a research hotspot in the field of cement-based materials science.Aiming to realize the self-healing of the cracks under the leaking condition,this study investigated the healing efficiency of different healing materials,with the permeability test with artificial cracks.The effects of the type and amount of the healing materials and the crack width on the healing efficiency were revealed;The healing efficiency of the physical-chemical two-component healing materials was also investigated,and the effects of the composition and the amount of the two-component healing materials and crack width on the healing efficiency were revealed;This study also revealed the composition of the healing products and the healing mechanism by using X-ray diffraction(XRD),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).The conclusion of this study includes:(1)With the same content of the self-repairing material and the same crack width,the healing efficiency of the physical healing materials was better than the chemical healing materials.Generally,the Super Absorbent Polymer(SAP),which is a type of physical healing materials,showed the best healing efficiency,and the CCCW is the best in all of the chemical healing materials.With the same self-healing materials and the same crack width,the healing efficiency was best when the content of the healing materials was 20%.SAP could repair the crack with a width up to 1.1 mm and CCCW could repair the crack with a width up to 0.5 mm,when the healing materials content was 20% and 0.4 mm was used as the harmless crack width threshold.(2)With the same content of the self-healing materials and the same crack width,the higher the content of physical component SAP in SAP/CCCW two-component healing material led to the better the healing efficiency.With the same composition of the two-component healing material and the same crack width,the healing efficiency was best when the content of the healing materials was 20%.The crack with a width up to 0.6 mm could be totally blocked when the SAP/CCCW two-component healing material was composed of 25%SAP and 75%CCCW,and the total content of healing materials was 20%.It was a greater improvement compared with the healing efficiency of single CCCW.(3)The quantity of healing products that formed by the reaction between the chemical healing materials and the water was still less in 2 hours.Therefore,the self-healing efficiency of the chemical components was not as good as that of physical components in this study.The cracking-healing property of CCCW mainly originated from the hydration of cement particles in CCCW.Its healing products had the binding effect and were not easy to be washed away by water flow,which was helpful for the healing of cracks under leakage.In addition,the healing mechanics of CCCW also included the formation of calcium hydroxide and calcium carbonate.SAP is flocculent and had a porous structure,which can absorb a large amount of water and expand.The combination of SAP and CCCW increased the amount and generation rate of calcium carbonate,which was benefit for the heling of the cracks. |
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