Preparation And Self-healing Behavior Of Cementitious Capillary Crystalline Waterproof Materials

Cementitious Capillary Crystalline Waterproof Materials(CCCW)is one kind of rigid waterproof material with outstanding self-heling ability and waterproof ability.It reduces the leakage of buildings effectively and has broad application prospect.However,the standardized mechanism of its self-healing ability still remains unclear,which limits the application of CCCW.The range of reactive chemicals focusing on the self-healing ability was given based on the analysis of a marketed product and characteristics of concrete.Reactive chemicals with good waterproof performance were found by exploratory experiments.The proportion of reactive chemicals was optimized through impermeability test.Based on the results,the rank of reactive chemicals according to their impact on self-healing ability was sodium silicate(83.3)> glycine(43.5)> sodium aluminate(40.5)> sodium carbonate(27.0)> tetrasodium EDTA(22.3).The optimize proportion of reactive chemicals was shown below: sodium carbonate 1.0%,sodium silicate 2.0%,sodium aluminate 1.0%,tetrasodium EDTA 1.0%,glycine 0.5%..Specimens with reactive chemicals showed higher preload repair rate in preload repair capability test,which proved the self-healing ability of CCCW.The optimize proportion of reactive chemicals was selected to prepare CCCW.Properties of CCCW were investigated in accordance with the National Standard GB 18445-2012.Test results indicated that CCCW could meet the specific standard and performed well.CCCW and the products after healing were observed through XRD,SEM analysis and mercury intrusion method.During the self-healing progress of CCCW,the consumption of CH,the production of CSH gel,calcium carbonate and ettringite were observed through XRD and SEM analysis.Besides,analysis of mercury intrusion showed that with reactive chemicals adding in,porosity was reduced from 37.0% to 26.9% and the average pore size was reduced from 156.9nm to 38.8nm.Meanwhile,the amounts of macro-pores over 100 nm decreased significantly.From the macro perspective,visual inspection and observation through 80 X optical microscope showed that a large number of white crystals with an average diameter of 0.2mm were generated.These white crystals generated on both sides of cracks so that cracks were healed by the accumulation of crystals.Mechanism analysis was raised to explain the self-healing behavior of CCCW based on all the test results and the characteristics of concrete.It was believed that the dissolution of CH,generation of CSH gel and ettringite,maintenance of the alkaline environment of cement,absorption of carbon dioxide,acceleration of the generation of calcium carbonate,enrichment of calcium ions by complexing agent,complexing-precipitation method that accelerating the generation of calcium silicate precipitation as well as the acceleration of the hydration of unhydrated cement particles had all contributed to the self-healing process.