Study On Preparation And Performance Of Underwater Self-Compacting Concrete For Canal Lining Slab Underwater Repair

The problem of concrete defects is widespread in various types of concrete structures,and the defects of underwater concrete structures are the most difficult to repair.Aiming at the difficult problem of repairing the lining slab of the water conveyance channel under the water transfer conditions of the water transfer project,a new type of concrete repair material which can meet the working performance required for underwater pouring,has good mechanical durability and is environmentally friendly is prepared.Based on the self-compacting concrete(SCC)mix ratio design method,this paper focuses on the durability design requirements of the channel lining slab concrete and the underwater repair construction performance,carries out the research on the workability,mechanics and durability of UWSCC,and proposes the water for working conditions UWSCC preparation technology for large area damage repair of channel lining slab.In this paper,first,through the cement slurry rheological test,using the cement slurry rheological parameters and rheological characteristics mathematical model,the influence of the material components on the cement slurry rheological properties was studied,and the high-fluidity and high-viscosity cement slurry was obtained.The suitable mixing range of each material composition,combined with the remaining water thickness theory,analyzed the mechanism of the effect of volume water-to-binder ratio,superplasticizer,flocculant,fly ash and silica fume on the rheological properties of the cenment slurry,provided experimental and theoretical basis for the adjustment of UWSCC working performance and mix ratio design.The UWSCC workability,mechanics and durability performance indexes were designed according to the water channel lining slab structure,underwater repair construction conditions and long-term operating environment of the project.The anti-dispersion property of underwater concrete was introduced as the standard for evaluating the anti-segregation performance of UWSCC,and put forward the control index of water-land intensity ratio.Combined with the research results of the rheological properties of the cement slurry,the mix ratio design and working performance and mechanical properties of the UWSCC were tested and verified,and the feasibility of the hydraulic SCC mix ratio design method for the UWSCC mix ratio design was demonstrated.On this basis,the systematic study of the influence of mineral admixture,sand ratio,water-to-powder ratio and other design parameters on the working performance and mechanical properties of UWSCC was conducted.The effects of different pouring methods on the mechanical properties of UWSCC were compared,and the UWSCC preparation technology was proposed.Based on a large number of test data,through theoretical research and regression analysis,a UWSCC working performance prediction model based on the ratio parameters of cement slurry was established.Finally,the durability of UWSCC was studied and compared with the durability of ordinary SCC.UWSCC has excellent durability against frost and impermeability,which is significantly better than ordinary SCC underwater.Mixed with fly ash and silicon fume,superplasticizer and flocculant significantly improves the anti-dispersion performance of the concrete and the durability of UWSCC while maintaining the fluidity of UWSCC.The qualitative analysis of the pore structure and micro-morphology of the cement slurry indicates that UWSCC has a more reasonable pore structure and micro-structure.