Study On Preparation And Chloride Resistance Performance Of All Solid Waste Marine Concrete Containing Ammonia-soda Residue

As a chemical waste in the production of soda ash,ammonia-soda residue(ASR)is difficult to utilised because of its fine particle size,high water content and complex composition.Aiming at the utilization of ASR,this paper studied the preparation of all solid waste marine concrete by ASR coupling metallurgical slag,desulfurization gypsum(DG)and iron tailings.The slump,compressive strength and chloride resistance performance of marine concrete under different conditions were studied.The hydration and hardening mechanism of all solid waste cementitious material containing ASR and the influence of steel slag(SS)to slag ratio and ASR to DG ratio on the hydration process were analyzed.Combined with the immersion test of high concentration artificial seawater,the changes of mechanical properties of concrete and the process of chloride corrosion during immersion were analyzed.Finally,the effects of dry-wet cycle,high-low temperature cycle and carbonization cycle on the mechanical properties and chloride resistance performance of marine concrete were studied.The results showed that when the ratio of ASR to DG is less than 2:3,the added ASR had little effect on the fluidity of concrete,and the compressive strength of concrete rose with the increase of ASR content.Due to the massive chloride salt in ASR,the electric flux of all solid waste marine concrete increased with the increase of the ASR to DG ratio.However,when the ASR to DG ratio was less than 2:3,the electric flux of concrete still met the requirements of marine environment.Under the optimum ratio of steel slag to slag ratio of 2:8,sand ratio of 0.50,water consumption of 140 kg/m3 and ASR to DG ratio of 2:3,the 180 days’ compressive strength of the concrete reached 73.8 MPa and the 180 day’s electric flux was 73 C.The main hydration products of all solid waste cementitious materials containing ASR included ettringite,Friedel’s salt and C-S-H gels.Among them,Friedel’s salt was formed by the reaction of dissolved aluminum octahedron from Al-O-Si bond broken of slag with Cl-.C-S-H gels with porous structure could solidify Cl-by physical adsorption.Under the combined action of these two ways,the negative effect of Cl-on the performance of concrete can be significantly reduced.When the ratio of ASR to DG is less than 2:3,the increase of the ratio promoted the formation of Friedel’s salt and C-S-H gels,which decreased the ratio of harmful porosity of 10～50 nm combining the physical filling effect of CaCO3 on paste pores.In the simulated marine environment test(high concentration artificial seawater immersion and composite cycle conditions),the all-solid waste marine concrete containing ASR showed excellent mechanical properties and chloride resistance performance.The compressive strength of the concrete was more than 60 MPa and the electric fluxes were less than 500 C.The preparation of all solid waste high-strength and high-performance marine concrete with ammonia-soda residue coupled with metallurgical slag can effectively improve the resource utilization rate of ammonia-soda residue,reduce the land occupation and potential environmental pollution risk caused by ammonia-soda residue stacking,and provide a theoretical basis for the application of all solid waste concrete in marine environment.