| Steel rebar reinforced concrete is one of the most widely used structural materials in infrastructure construction over the world.During the service period,steel rebar corrosion frequently occurred caused by concrete leakage.Cracks are the main reason for the leakage of concrete structure.At present,using flexible waterproof materials are the major method to prevent concrete leakage.However,flexible waterproof materials are weak on durability,environmental friendship,and compatibility with concrete matrix,which don’t adapt to the development of building waterproof industry.Rigid waterproof material is one kind of waterproof materials with outstanding permeability resistance and repaired properties,which can promote the self-healing of concrete.However,the standardized mechanism of its self-healing ability is still unclear.In this thesis,based on the analysis of concrete composition,active materials were selected to prepare a kind of internal waterproof material(FS waterproof material for abbreviation),and the key properties of waterproof concrete was investigated to reveal the mechanism of waterproof properties.Four active chemicals,including sodium citrate,sodium sulfate,aluminum silicate and sodium methyl silicate were available in this study.Based on orthogonality analysis method,compressive strength,electric flux,and impermeability pressure of concrete with different dosage of active chemical materials were studied.The results shown that,sodium citrate was most benefited for compressive strength,while electric flux was most affected by aluminum silicate.The influence of active chemical substances on the primary impermeability pressure ratio of mortar was: aluminum silicate>Sodium citrate >Sodium sulfate>Sodium methyl silicate.The optimal ratio for active chemical were determined as sodium sulfate: aluminum silicate: sodium methyl silicate = 1: 8: 6: 2.According to the national standard "cementitious capillary crystalline waterproofing material"(GB 18445-2012),the properties including appearance,water content,fineness,et.al of waterproof material was investigated.The results shown that the primary impermeability pressure ratio of concrete was 250%,the secondary impermeability pressure ratio was 175%,and other properties were all followed the standard requirements.The effect of FS waterproof materials for concrete with different permeability grade was investigated,the results proved that,the flexural strength of low permeable concrete,medium permeable concrete and high permeable concrete was increased 7.6%,4.5% and3.4%,respectively,and the decline of porosity was 2.5%,11.0% and 11.1%.The electric flux was decreased 54.3%,56.0% and 49.0% as well.These results proved that FS waterproof performed the best for medium permeable concrete.For pre-stressed concrete,with the addition of 3.0% of FS waterproof material,the recovery ratio under standard curing,soaking curing and ambient curing was 141.5%,142.5% and 131.8%,respectively,after 56 days.The results demonstrated that the moisture was important for concrete selfhealing with FS material.The hydration and micro-morphology of FS waterproof concrete were studied by XRD and SEM,and the results shown that,the active chemical components in concrete reacted with hydrated calcium hydroxide to form calcium silicate hydrate and ettringite,and these products were preferred in pores and cracks.The mechanism of waterproof behavior was supposed as: FS waterproof materials promoted concrete more crystal hydration products in pore and crack zone,which filled the space and making a denser structure.Figure: [thirty-nine],Table: [twenty-four],Reference: [eighty]... |
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