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Study On The Marine-Sand-Chloride Binding Mechanism Of Cementitious Materials

Posted on:2022-09-25Degree:MasterType:Thesis
Country:ChinaCandidate:M SunFull Text:PDF
GTID:2491306566960659Subject:Architecture and Civil Engineering
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As a non-renewable resource,river sand is one of the indispensable raw material for concrete structures.The rapid development of the construction industry has led to an increasing shortage of river sand.In recent years,the marine sand has received extensive attention as viable alternative material to river sand.The concrete with marine sand is corroded by chloride salt in the marine environment,which makes the concrete structures face seriously durability problems.However,the hydration products could bind part chloride ions in the concrete and improve the durability of concrete structures.Therefore,the exploration of the chloride binding mechanism of concrete made with marine sand is very important for predicting the service life of concrete structure and durability design accurately.The chloride binding capacity of mortars under standard curing conditions,the immersion of chloride salt solution and accelerated carbonation were studied in this study respectively.The effect of metakaolin,fly ash,alumina and aluminous cement on the chloride binding capacity of mortars were investigated.And the effect of chloride binding on hydration products and pore structure were analyzed by energy spectrometer(EDS),X-ray diffraction(XRD),derivative thermogravimetric method(DTG),mercury intrusion method(MIP)and scanning electron microscope(SEM).The contents of the research work and main conclusions are summarized as follows:(1)The same amount of chloride ions were introduced to mortars by marine sand and mixed water respectively.The effect of chloride ions introduced way,supplementary cementitious materials and the cement type on chloride binding capacity were analyzed.The results show that there is a diffusion process of chloride ions from surface of marine sand to cementitious materials,and that chloride ions introduced by mixed water distribute evenly in mortar.Introducing chloride ions by marine sand to study chloride binding capacity of mortars made with marine sand is more instructive compared with chloride ions introduced by mixed water.10% metakaolin contents(mass fraction)could increase the chloride binding capacity of mortars to the two types of doped chloride ions.With the increasing of the metakaolin contents,the increasing of chloride binding capacity gradually weakens.Compared with cement mortar,the aluminous cement mortar has higher chloride binding capacity.(2)The chloride binding capacity of different mortars under the immersion of chloride salt solution were studied.And the effect of supplementary cementitious materials and the cement type on chloride binding capacity were analyzed.The results indicate that the chloride ions introduced by marine sand could decrease the intrusion amount of external chloride ions in mortars.Compared with cement mortar,the chloride ions introduced by marine sand have more benefit effect on pore structures of aluminous cement mortar,and the aluminous cement mortar has higher chloride binding capacity on external chloride ions.10% metakaolin contents(mass fraction)could increase the chloride binding capacity of mortars to the external chloride ions.(3)The influence of carbonation on chloride binding in different mortar were investigated.The chloride ions redistribute and two peak value of chloride content occur in mortars under carbonation.The bound chloride could almost completely release in the fully carbonized zone of mortar,and the release effect on bound chloride gradually decrease with depth.The chloride binding rate in mortar could be divided into three parts after carbonation with depth: the section of low chloride binding rate,the section of increasing chloride binding rate and the section of stable chloride binding rate.
Keywords/Search Tags:mortars made with marine sand, chloride binding, supplementary cementitious materials, chloride corrosion, carbonation
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