The Influence Of Sea Sand And Sea Water On The Performance Of Cement Mortar

In the islands and coastal areas,due to the shortage of river sand resources,sea sand and sea water resources will inevitably become the choice of Marine construction projects.However,due to the large difference in composition,gradation and performance of sea sands from different sources,and the adverse impact of inorganic salt ions in sea sands and sea water on the durability of concrete,the use of sea sands and sea water in Marine engineering is limited.In view of the above problems,this paper studied the influence of sea sand on the performance of Portland cement mortar,and compared it with standard sand.Due to the short setting time,early strength,high the ability to resist chloride ion diffusion and good durability advantage of sulfoaluminate cement,this paper used the sulfoaluminate cement to prepare sea mortar,analyzes the influence of seawater and sea sand on cement gel material,and studied the volume stability and mechanical properties of sulfoaluminate cement mortar in different curing environment.Finally,the influence of seawater and seawater environment on the mechanical strength and volume stability of the cement paste was studied,the internal mechanism was verified by means of a variety of modern test methods.The main conclusions are as follows:(1)Curing in the fresh water environment,fly ash and slag was used to modify the sea sand mortar,making the ability to resist chloride ion diffusion of the sea sand mortar improved by 15.8%.As the uneven surface,coral sand can be closely bonded with the hardened cement paste,which limits the shrinkage of cement matrix and makes the volume stability of coral mortar better than that of standard mortar.The mechanical strength of sea mortar was lower than that of standard mortar,but by mixing fly ash and slag,the microstructure of cement matrix and interface transition zone were improved,and the mechanical properties of sea mortar were strengthen.The 28 d compressive strength was 2.08% higher than that of standard mortar.(2)Curing for 59 days in fresh water environment,the volume shrinkage of sulfoaluminate cement mortar was more obviously larger than that of Portland cement mortar.Portland cement or sulfoaluminate cement,the volume stability of mortar mixed with sea sand was better than that of the same cement mortar mixed with standard sand.Through the analysis of ac impedance test,the sulfoaluminate cement mortar mixed with standard sand was better than the other three kinds of mortar in the density and the content of hydration products.At these two points,the sulfoaluminate cement mortar mixed with sea sand was worst.The flexural strength of sulfoaluminate cement mortar was obviously inferior to that of Portland cement mortar.Curing for 7 days,the compressive strength of the two kinds of Portland cement mortar was weaker than that of the sulfoaluminate cement mortar mixed with standard sand,but stronger than that of the sulfoaluminate cement mortar mixed with sea sand.(3)Curing in the seawater environment,portland cement or sulfoaluminate cement,the volume stability of sea sand mortar was better than that of standard sand mortar,and the volume stability of sulfoaluminate cement mortar was better than that of Portland cement mortar.Through the analysis of ac impedance test,sulfoaluminate cement mortar mixed with standard sand in the density and the content of hydration products were superior to the other three groups of mortar,but the sulfoaluminate cement mortar mixed with sea sand was far worse.Through curing of sea water,the density of sulfoaluminate cement mortar mixed with sea sand can be improved;Inorganic salt ions in seawater can promote the early strength of cement gel products.(4)By mixing fly ash and mineral powder,the mechanical strength of Portland cement mortar was greatly improved,but the mechanical strength of sulfoaluminate cement mortar was obviously reduced.After mixing microcrystalline cellulose,the volume expansion and shrinkage of sulfoaluminate cement and portland cement was reduced,especially for sulfoaluminate cement.