Study On The Cl~- Binding Capacity Of Sulphoaluminate Cement With Cl~- Incorporation And Its Evolution During Service

It has been an important method for Chinese marine strategy and costal provinces'economic development to reasonably use marine aggregate and sea water for infrastructure construction.The priority request for using such marine resource is reduing the risk from Cl^-introduced to the concretes on reinforcement of the structures.In this dissertation,the following contents have been studied:the influence of key parameters and use of supplementary cementitious materials on hydration,mechanical and shrinkage of CSA,which inherently able to bind significant amount of free Cl^-was studied,and the capacity and the mechanisms for binding of Cl^-introduced by raw materials during mixture were explored;meanwhile,the influence of high temperature,CO₂ and sulphates on the Cl^-binding capacity during the service of structure was evaluated;furthermore,the real protection of CSA on reinforcemen once Cl^-was introduced via raw materials was assessed.Detailed outcomes of this work can be summaries as follows:1.A higher Cl^- binding capacity can be achieved once a higher w/b raio is selected and minimum amount of gypsum is added in mixtures.In this case,production of AFm and aluminum gel are dominant reaction kinetic;2.The presence of supplementary cementitious materials?Calcium carbonate,Slag,Fly ash and Metakaolin?shorten the setting time of the containing-gypsum cement,but extends the setting time of the gypsum-free cement;the averall Cl^-binding capacity is increased with the existence of supplementary cementitious materials and the Cl^-binding capacity of containing-gypsum samples and the gypsum-free samples are about 15%and 40% respectively;3.The influence of high temperature on the Cl^-binding capacity is slightly less than the sulfate attact,and both show a downward trend.After carbonation,the Cl^-binding capacity of containing-gypsum CSA samples decreases;duo to the calcium carbonate may lead the internal Cl^-to a self-sealing effect,the binding capacity of gypsum-free CSA cements increase to more than 90%;4.CSA cement has a good Cl^- binding capacity,which makes the internal steel corrosion resistance more than PC cement,especially the free-gypsum CSA cement has a higher linear polarization Rp.In summary,by adjusting the parameters of CSA cement,the prepared CSA cement has a better Cl^-binding capacity and a higher corrosion resistance for the internal reinforcement than the PC cement.It lays the foundation for the practical engineering application of marine aggregate and sea water.