Study On Optimization And Modification Of Ferrochrome Slag As A Substitute Aggregate For Natural Sand

In this paper,the ferrochrome slag replaces the natural sand as the starting point,through the study of particle grading optimization and surface modification of ferrochrome slag to reduce its voidage and porosity,so that it can become the high-quality substitute fine aggregate of natural sand,and serve as the fine aggregate for mortar or concrete.It not only solves the serious shortage of natural sand but also reduces the comprehensive cost of concrete.It also relieves the environmental pressure,which is of great significance for the reuse of solid wastes and the conservation of resources.This study provides a reliable basis for the resource development and utilization of ferrochrome slag and has the benefit of energy conservation and emission reduction.Combining with the ferrochrome slag production process,analyzing the solid waste index and basic properties,the results show that ferrochrome slag has potential resource properties as an alternative fine aggregate.When raw ferrochrome slag is used to prepare mortar and concrete,it is found that it can only replace 20% of the natural sand.When more than 20%,the mortar or concrete will show serious bleeding and poor workability.The chemical analysis,XRD and SEM observation,density test,sieve analysis and other physical and chemical performance tests of ferrochrome slag show that its particle gradation performance is poor,showing the gradation characteristics of "large in the middle,small at both ends".According to the principle of filling put forward "geometric analysis of sieve residue curves" new gradation optimization method,get graded optimization fine packing material particle size range,filling quantity and proportion;In this paper,the eolian sand and the ground chromium iron slag were used to fill 30% instead of the raw ferrochrome slag,and two kinds of optimized ferrochrome slag fine aggregate were obtained respectively.Based on two kinds of optimized ferrochrome slag aggregate,the maximum accumulation density theory and the mortar strength test,it is determined that the ground ferrochrome slag with a 30% particle size range of less than 0.6 mm and 70% raw ferrochrome slag can replace the 100% natural sand.Grain size distribution optimization reduces the porosity of ferrochrome slag.Because the ferrochrome slag is rough surface,the appearance of the opening hole assembled structure morphology,it presents the characteristics of high porosity,high pressure crushing value and high water absorption rate.When ferrochrome slag is used as the fine aggregate of mortar or concrete,mortar or concrete due to the increased by mixing water with poor water retention problems.The surface modification of the optimized ferrochrome slag was studied by taking into account the interface structure and bonding strength of the alternative fine aggregate and cement slurry by referring to the robustness index of the aggregate and comparing it with the natural sand.The modifier suitable for ferrochrome slag was designed by orthogonal test,based on the principle of the wall building,ferrochrome slag was modified to give full play to the advantages as a high-quality fine aggregate to replace natural sand.The saturated surface dry water absorption of modified ferrochrome slag was reduced by 65%,while the crushing value of 2.36-4.75 mm particle grade modified ferrochrome slag was reduced by 50%,and the mortar strength prepared with modified ferrochrome slag was increased by 31%.In this paper,the modification mechanism of the modifier on ferrochrome slag was studied by means of micro-experiment,the influence relationship of the modification research on ferrochrome slag was combed by decoupling method,and the four factors of modifier were analyzed qualitatively to quantitatively by influencing the dry water absorption of the saturated surface of ferrochrome slag and then affecting the water-binder ratio and affecting the strength of concrete,indicating that the modified ferrochrome slag had a beneficial effect on the interface performance of concrete.The modified ferrochrome slag was optimized by the new grading method,and the optimized modified ferrochrome slag with low voidage and porosity was obtained,that is,the high-quality substitute fine aggregate of natural sand.Based on the optimization of the key properties of the modified ferrochrome slag,the mortar shrinkage test and the concrete anti-freezing performance test were carried out.Analysis to optimize the pore structure of cement mortar and concrete modified ferrochrome slag mechanism,detection effect of its application in the mortar and concrete.The high quality substitute fine aggregate of natural sand can replace the 100% natural sand in mortar or concrete,which can give full play to the high quality aggregate performance.