Research On The Performance And Self-Healing Effect Of Microcapsule Based Self-healing Cementitious Composites

Concrete is the most important building material in the construction industry.However,due to its inherent performance defects,under various internal and external factors,concrete will inevitably develop micro-cracks during the early construction stage and later service stage.Microcapsule self-healing technology is dedicated to self-perception and self-healing of concrete cracks.The self-healing agent,urea-formaldehyde resin/epoxy resin microcapsules with the average particle size of 536.00?m,were synthesized.And the imidazole MC120D was used as solidified agent in this thesis.Different dosage microcapsules of 1.5%,3.0%and 4.5%of cement weight were mixed respectively into cement mortar.Then the strength,impermeability and self-healing property of cement mortar were investigated at different curing ages of 7d,14d and 28d.The microstructure of the mortar is observed by optical microscopy and SEM-EDS.At the same time,Mercury intrusion porosimetry(MIP)measured the parameters of cement mortar hole structure,and the porosity curve and pore diameter distribution curve were obtained.This thesis is divided into the following sections:(1)The strength and impermeability of cement mortar were tested,and the permeation height of the specimen profile was used to reflect the impermeability of the mortar.After the addition of microcapsules,the flexural strength and compressive strength of cement mortar were significantly reduced,and the compressive strength of the test group was only 60-70%of that of the control group without mixed microcapsule.However,the content of microcapsule had little influence on the strength of mortar,and the change range of compressive strength of mortar between the three contents of microcapsules did not exceed 10%.The incorporation of microcapsules also reduced the impermeability of the mortar,and under the effect of pre-damage,the impermeability of the microcapsule mortar decreased more.(2)70%of the maximum load was applied to the mortar to get the pre-damage of the mortar,and these damaged mortar specimens should be cured when they had been placed in the dry curing room or the standard curing room for 7 days.Then these specimens were re-tested to get their performance.The test results showed:under the dry curing condition,all the mortars of 7-28d curing ages had self-healing effect,and the healing effect of microcapsule based cement mortar was better than that of the mortar of the control group.With curing age growing,the self-healing ability of microcapsule based cement mortar gradually decreased and tended to be stable.Under the standard curing condition,the self-healing effect of mortar was weaker than that under the dry condition.For the healing of mortar compressive strength,4.5%-doped mortar did not recover its strength at the curing age of 14 days,and all mortars at mature age didn't complete the self-healing of strength.And the healing effect of microcapsule based cement mortar impermeability decreased with cruing age growing.(3)The results of the microstructure test showed that the microcapsules broke as the cracks developed in the mortar and provided repairing effect.MIP results showed that microcapsules had good self-healing effect.For 7d curing age,microcapsule based cement mortar can effectively reduced its porosity by repairing.And the microcapsule mortar at mature age still had the effective repairing effect under the dry curing conditions,and the porosity percentage decreased by 1.99%.However,under the standard condition,the porosity of the microcapsule mortar could be restored to the state before the pre-damaged,but the healing effect was significantly reduced compared with the dry cultivation.