Study On Chloride Binding Properties Of Cement Mortar Made Of Washed Marine Sand

Chloride ingress is the main reason that affects the structural damage of reinforced concrete structures,in the marine environment.The durability of structures under chloride ion environment has attracted much attention.The chloride ions in reinforced concrete structures are mainly derived from external environment and raw materials themselves.Due to the increasing lack of river sand resources,washed marine sand is gradually used as raw materials for buildings or structures in coastal areas.Therefore,it is very important to study the binding of chloride ions in desalinated sand-cement-based materials for the durability of reinforced concrete in marine environment.In this paper,the chloride binding properties of cement mortar made of washed marine sand were studied,in standard curing environment,chloride salts environment and sea water environment.The main findings are as follows:In this paper,cement mortar specimens were prepared with chloride-containing fine aggregate(sea sand and washed marine sand).The chloride-binding properties of washed marine sand cement mortar were studied under standard curing environment.The relationship between free chloride ion and total chloride ion in cement mortar was obtained.The chloridebinding property of cement mortar was evaluated under the condition of internal chloride ion addition.The evaluation index provides a basis for comprehensively and accurately describing the chloride binding properties of cement mortar.The erosion process of chloride ions in cement mortar and the bonding performance in cement mortar were studied.The results show that the free chloride content distribution of cement mortar samples increases firstly,then decreases and finally tends to be stable with the extension of immersion time.According to the different mechanism of chloride migration,cement mortar can be divided into capillary adsorption zone and diffusion zone from surface to interior.The chloride bonding performance of washed marine sand cement mortar in the marine underwater environment is studied based on the actual working conditions.The results show that the penetration depth of chloride ion is deeper in the presence of sulphate,and sulphate has adverse effect on the chloride binding property of cement mortar.The binding products of chloride ions in cement mortar were characterized by SEM-EDS,XRD,TG-DTG,MIP and FTIR.The results show that the microscopic test results are consistent with the macroscopic conclusions.Chloride ion has a certain effect on the microstructure of cement mortar.The bonded products can fill the pores of cement mortar,thus reducing the porosity and optimizing the pore structure.Because of the expansibility of the product of the combination of sulfate and cement mortar,sulfate has adverse effect on the microstructure of cement mortar.Moreover,microscopic experiments also show that the presence of sulphate is not conducive to the combination of cement mortar and chloride ion.