| Admixtures are fine inorganic mineral powders that replace part of the cement and improve the performance of concrete when preparing concrete.Steel slag and sludge are common industrial solid wastes in the iron and steel industry,with large output and low consumption.A large amount of steel slag accumulates,not only occupying land,but also causing environmental pollution,which seriously affects our country’s scientific strategy for sustainable development.However,steel slag and sludge contain substances similar to cement,which have potential hydration properties and are suitable for the preparation of highly active admixtures.This is of great significance to the resource utilization of industrial solid waste.The research of this article is to meet the requirements of the enterprise.It takes steel slag and sludge as raw materials,mixes slag and fly ash,adds grinding aids and activators to grind to a certain fineness,and prepares steel slag that meets S95 grade.Base admixture.And based on the prepared admixture,ordinary Portland cement clinker and gypsum are added to prepare a P·C 42.5 that meets the standard.This can not only use steel slag in bulk,but also solve the problem of shortage of cement resources in the concrete industry.In line with the economic strategy of circular development,coupled with the new materials that are national policies to encourage development,its development prospects are very broad.In this thesis,combined with the preparation process of the admixture,we explored suitable grinding aids and stimulators,and obtained the following conclusions during the research process:(1)Under the requirements of the enterprise,take the mass ratio of steel slag:slag:sludge:fly ash=32:40:13:15 as raw materials to explore suitable grinding aids.According to experimental research,the best grinding aid is triethanolamine,and the effect is best when the dosage is 0.5‰.When the mass of the material is 8kg,adding a grinding aid and grinding for 1 hour,the sieve residues of 45 μm and 80μm are reduced by 2.2%and 15.6%respectively compared with the comparison experiment,the grinding aid effect is more obvious,and the 28-day activity index is improved 7.3%.(2)Under the material ratio of steel slag:slag:sludge:fly ash=32:40:13:15,add different activators to explore suitable activators for the system.Research shows that Na2SO4,silicon slag and desulfurized gypsum have the best effects.Orthogonal experiments were designed with Na2SO4,silicon slag and desulfurized gypsum.According to the results of the orthogonal experiment,there is a synergistic effect among the stimulators,and the best effect is when the content of Na2SO4,silicon slag and desulfurized gypsum are 2.0%,0.5%and 1.5%,respectively.At this time,the activity of the admixture is greatly improved.The activities of 3d,7d and 28d are 77.3%,85.9%and 96.6%respectively,which are increased by 24.2%,25.4 and 22.4%respectively,which meet the technical indicators of S95 level.(3)According to the analysis of XRD and SEM,the hydration products of the admixture of ingredient 1 are C-S-H,Ca(OH)2 and AFt.After adding the activator,the content of C-S-H and AFt of the admixture increased,but the content of Ca(OH)2 decreased,and the system structure of the specimen was more compact.It shows that the stimulant can promote the hydration of the admixture of ingredient 1.(4)In order to further increase the proportion of steel slag in the steel slag-based admixture,maximize the use of steel slag under the conditions of stability.The mass ratio of the best ratio obtained by the compounding method is steel slag:slag:sludge:fly ash=40:30:15:15.When 0.5‰ of triethanolamine is added and 8kg of material is ground for 1 h,The activity of the admixture is slightly lower than the admixture ingredients provided by the enterprise,but there is not much difference.However,the utilization of steel slag and sludge is increased by 10%,which is beneficial to the comprehensive utilization of steel slag.The 3d,7d and 28d activity of the admixture of ingredient 2 is 67.2%,74.7%and 85.8%when activator A is added,and the activity reaches the technical index of S85 level.(5)Under the admixture of ingredient 2,add different surfactants,and it can be obtained through single factor experiment that the admixture of ingredient 2 has a better excitation effect when adding wood calcium.The effect is best when the content of wood calcium is 2.5‰,and the 28-day activity index increases by 10.8%.Taking activator A and 2.5‰ wood calcium compound as activator B,after adding activator B,the activity index of the admixture of ingredient 2 for 3 days,7 days and 28 days is 72.0%,81.3%and 98.5%,reaching S95 technical indicators.(6)According to XRD and SEM analysis,the hydration products of the admixture of ingredient 2 are C-S-H,AFt and Ca(OH)2.After adding activator A and activator B,the content of C-S-H and AFt in the hydration product increased,but the content of Ca(OH)2 decreased.And after adding the activator B,the dispersibility of the gelling material in the hydration process is better,the gelling materials are not easily wrapped,and the hydration rate of the gelling material is increased,which is manifested by the increase in the strength of the corresponding test piece.(7)The admixture of ingredient 2 is added with activator B as the main material,and 25%clinker and 5%gypsum are added to prepare composite cement that meets the P·C 42.5 standard in the national standard,and can make large use of steel slag and other industries in the iron and steel industry.Solid waste.The admixture of ingredient 2 is added with activator B as the main material,and 45%clinker and 5%gypsum are added to prepare cement.The performance is similar to the commonly used P·I 42.5 grade in the market,which has strong competitive advantages and broad application prospects.,The market potential is great. |
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