Research On Structure, Performances And Applications Of Sulfoaluminate Cement High Performance Concrete

With development of concrete science and technology, utilization scopes of concrete buildings become increasingly wide. Building concrete engineering are required in many regions with bad environment conditions, thus, concrete used in these regions should have superior durability to ensure the working life of the buildings. Based on the development and utilization of Portland cement-based concrete, combining with deterioration reason of the concrete performances in many special locations, a developing consideration using sulfoaluminate cement-based high performance concrete(HPC) to replace Portland cement-based concrete is advanced to achieve the goal of adjusting measures to local conditions and scientific development.Sulfoaluminate cement (SAC) has many superior properties such as rapid hardening, early strength, high strength and resistance of sulphate and chlorine erosion. The purpose of this paper is to improve sulfoaluminate cement-based HPC production technology by learning from the application technology of Portland cement-based HPC.First, performance optimization of SAC was investigated based on the advantages of SAC, so as to overcome the existed performance deficiency. Retarder H which could effectively control fast-setting of SAC and high-effective water reducing agent AS that could be compatible with SAC and improve compressive strength of SAC were studied respectively. Superfine slag and fly ash were compounded taking advantage of each of their performance merits. 20% compounded blending was used to replace SAC to solve problems of SAC fast hydration exothermic velocity. Besides, adhesion agent was also used to solve problems of separation, crustification and bleeding.Influences of water cement ratio, compounded mixture, air-entraining agent etc on mechanical properties of sulfoaluminate cement-based HPC were studied. Comparing with performance of Portland cement-based HPC, sulfoaluminate cement-based HPC was proved to have characteristic of higher early strength and steady later strength increase. The durability of sulfoaluminate cement-based HPC was studied. The sulphate resistance characteristic of sulfoaluminate cement-based HPC with compounded blending was validated under different cement water ratio. The influences of water cement ratio, compounded blending and air-entraining agent on impermeability, frost resistance and carbonation resistance of sulfoaluminate cement-based HPC were also studied, meanwhile by comparision with Portland cement-based HPC under the same conditions and, carbonation and life prediction of protected layer models were also established.Structural appearance and character of sulfoaluminate cement-based HPC were observed using SEM. The influences of water cement ratio, compounded lending and air-entraining agent on concrete structure and interface were compared, and the structural character changes of sulfoaluminate cement hydration products before and after carbonation were analyzed. The energy spectra analysis results proved that carbonation could lead to AFt decomposition. The changes of sulfoaluminate cement hydration and carbonation products were also analyzed using XRD. The results proved the disappearance of AFt characteristic peaks after carbonation. Porosity variation and pore structure distribution of sulfoaluminate cement-based HPC after adding blending and air-entraining agent were measured using MIP, meanwhile the mechanism of air-entraining agent on improving frost resistance of concrete was analyzed.The disease principle and repairing program of Jinshagang Bridge in Yantai-Weihai highway were studied. Application schemes of sulfoaluminate cement underwater non-dispersed concrete and sulfoaluminate cement-based HPC were established, which was successfully applied to repair the bridge corroded by sea water.Analysis above showed that water cement ratio and setting time of sulfoaluminate cement could be effectively controlled by using high-effective water reducing agent AS and retarder H. The strength of sulfoaluminate cement-based HPC could be improved remarkably when decreasing water cement ratio, and superior mechanical properties could also be obtained by controlling water cement ratio less than 0.38. Sulfoaluminate cement by adding 20% blending has good ability to resist erosion from sulphate and magnesium salt. The additive of blending could improve performance of concrete to resist carbonation, while decrease the frost resistance and impermeability of concrete. The frost resistance of concrete could be improved by adding air-entraining agent, however, the impermeability and carbonation resistance would also be decreased.Based on above results, different sulfoaluminate cement-based HPC could be fabricated through scientific mixing ratio to promise the engineering safety for different performance requirements.In all, based on scientific theory and advanced technology, combining with performance merit of materials, this paper, from the deterioration reason of concrete materials, combining with internal cause effect of optimization, aims to improve structure and performance of materials as well as erosion resistance and destruction from external cause. Besides, this paper also attempts to contribute on solving present durability crisis of concrete by using sulfoaluminate cement-based HPC scientifically and reasonably.