Study On Preparation And Performance Of Sulfate-resistant Gelling Materials

Sulfate erosion is one of the main factors for the deterioration of concrete service performance.Different sulfate environments have different effects on the performance of concrete.The traditional production process of Portland cement consumes a lot of resources and energy,leading to serious environmental pollution.Moreover,it cannot meet the increasingly high performance requirements of social development.Thus,in our study,mineral admixtures such as fly ash,mineral powder,desulfurized gypsum,silica fume,etc.are mixed with ordinary Portland cement to prepare a cementitious material which exhibit high resistance to sulfate erosion.Compared with ordinary cementitious materials,the materials we prepared displays better resistance to sulfate erosion and ensures its mechanical properties meanwhile.We draw much attention to investigating the macro-mechanical properties,phase composition and pore structure of various groups under different sulfate erosion environments.The main contents and relevant results are as follows:(1)Based on the orthogonal test,the inspection index is the corrosion resistance coefficient.The influence of the proportions of the four mineral admixtures of fly ash,silica fume,slag powder and desulfurized gypsum on the sulfate corrosion resistance of the cementitious material is studied.The following conclusions are drawn:the primary and secondary order of the factors affecting K_Cobtained from the orthogonal test is fly ash>ground granulated blast furnace slag>silica fume>desulfurized gypsum.Obtain the optimal composition of the high corrosion-resistant cementitious material(HCRC1):m(cement):m(fly ash):m(ground granulated blast furnace slag):m(silica fume):m(desulfurized gypsum)=26:15:50:6:3.(2)To study the macro-mechanical properties of different ratios of cementitious materials under sewage immersion,analyze the pore structure of each group of cementitious materials and the changes in phase composition before and after the sewage immersion.The results show that as the curing time increases,the compressive strength of the cementitious material cured by fresh water increases,but it increases first and then decreases when immersed in sewage,and the corresponding compressive strength ratio K_fgradually decreases.The K_fof HCRC1 soaked in sewage for 100 d is 37.94%which is higher than that of ordinary Portland cement.The erosion products produced are mainly gypsum crystals,and the content of HCRC1 erosion products is the lowest.A large number of mineral admixtures replace cement to make the system structure more compact,effectively refine the pore size,and make the pores in the slurry close to the harmless pores.(3)The mechanical properties of cementitious materials with different proportions under high sulfate dry wet cycle and the micro phase composition before and after dry wet cycle were studied.The results show that the compressive strength of each group of mortar first increases and then decreases under the high sulfate dry wet cycle environment.The compressive strength of HCRC1 was 21.2%which is higher than NC and HCRC2 group after 100 days of dry wet cycling.Gypsum type erosion plays a leading role in the dry wet cycle.Gypsum in HCRC series is significantly lower than that in NC,especially HCRC1.(4)Study the macro-mechanical properties of different water-binder ratio cementitious materials in sewage environment,analyze the pore structure of each group of cementitious materials and the phase composition after sewage immersion.When the water-to-binder ratio changes within the range of 0.35 to 0.5,the compressive strength increases with the decrease of the water-to-binder ratio,which has a more significant impact on the early strength.As the immersion time increases,the strength of each group of mortars immersed in the sewage increases first and then decreases,while the K_fdecreases rapidly.As the water-to-binder ratio decreases,the amount of erosion products produced also decreases.The MIP test shows that the cumulative pore volume and total porosity of each sample decrease with the decrease of water-binder ratio,and the cementitious material becomes denser.