Efficient Utilization Mechanism And Application Technology Of Waste Residue In Commercial Concrete Mixing Plant

The waste residue from commercial concrete mixing plant is the bulk solid waste generated during the operation and maintenance of the mixing plant.The existing treatment method of the waste residue has a high cost,a large environmental impact,a low added value and a lack of large-scale practical engineering application,which limits the efficient use of the waste residue.To solve this problem,this paper carried out the efficient utilization mechanism and application technology development of the mixing station waste residue.Based on the analysis of the physicochemical and grinding characteristics of the mixing station,the activation technology of the mixing station waste residue was proposed.The multi-industrial waste residue composite admixture mainly composed of mixing station waste residue is designed and developed.Special chemical admixtures suitable for composite admixture were designed and developed.The key technology of industrial production of composite admixture by mixing station waste residue was mastered.The main work and achievements of this paper are as follows:1.Chemical composition analysis,XRD test,electron scanning microanalysis and thermogravimetric analysis were carried out to study the physical and chemical properties and microscopic morphology of the mixing station waste residue.The main chemical composition of the mixing station waste residue is silicon and aluminum oxide.The surface of the waste residue is loose and porous,and there is still a large amount of spherical particles of fly ash.From the characteristics of waste residue,it is feasible to use the waste residue of the mixing station as a concrete admixture.2.Using the specific surface area,45?m and 80?m sieve residue to analyze the grinding characteristics of the mixing station waste residue,it can see that the fragility of the mixing station waste residue is good,and the specific surface area of waste residue grounded for 30 min can be more than 500 m~2/kg.However,the mixing station waste residue has a large loss of ignition,a high content of stone powder,a large water demand,and it is easy to stick ball when grinding alone.In addition,when the mixing station waste residue is used alone as the admixture,the allowable dosage is low,the initial fluidity of the cement-based material is reduced,the loss rate over time is increased,and the compatibility with the water reducing agent is poor.3.The incorporation of the mixing station waste residue will reduce the strength of the mortar,while the reduction of the mortar strength can be significantly reduced for the grounded mixing station waste residue with a quantity not exceeding 30%.The furnace slag can delay or eliminate the phenomenon of ball entrapment when the mixing station waste residue is grounded alone,and improve the grinding efficiency.The addition of water granulated slag can optimize the overall friability of the material and improve the mechanical properties and working performance of the composite admixture.4.Based on factors such as grinding characteristics,activity,workability and water reducer compatibility,two types of composite admixture are developed.The optimal ratio of the a-type composite admixture is furnace slag:mixing station waste residue=7:3,the best grinding time is 40 min,the 45?m sieve residue is 12.5%,the specific surface area is 594 m~2/kg,and the 28d activity index is 78%.The optimal ratio of the b-type composite admixture is mixing station waste residue:furnace slag:water granulated slag=3:3:4,the best grinding time is 40 min,the 45?m,the sieve residue is 15.6%,the specific surface area is 476 m~2/kg,and the 28d activity index is92%.5.The hydration products and microstructure of composite admixture cement-based materials were systematically studied by microscopic testing methods such as XRD,TG-DSC,SEM-EDXA,pore solution,electrical resistivity and pore structure analysis.With the incorporation of composite admixture,the total exotherm of cement-based materials,the rate of heat release during accelerated hydration and the hole solution alkalinity were declined.Moreover,since the composite admixture can better filled between the cement hydration products in the later stage of hydration,the number of harmful pores and harmful holes in the cement-based material is reduced,and the pore structure is optimized.6.Using a novel polymer structure that protects against slump loss and mud,through the regulation of molecular structure and chemical modification of the carboxyl groups on the molecular chain,a composite protective polycondensate for the preparation of concrete with high content of composite admixture was developed.In the C20-C70 concrete,when the content of the substituted mineral admixture is25%,the incorporation of the a-type and b-type low-carbon admixtures respectively has no effect on the compressive strength of the concrete at 28d.The incorporation of composite admixture can improve the chloride ion penetration resistance of concrete.The dry shrinkage of the pure cement concrete is significantly greater than that of the concretes containing fly ash,slag and composite admixtures,respectively.In the early stage of cement hydration,the shrinkage rate development trend of the concretes mixed with the three kinds of admixtures is basically the same,but with the increase of age,the two composite admixture concretes are lower than ordinary concrete,especially the concrete blended with b-type composite mixture.The carbonation resistance of concrete mixed with a-type and b-type low-carbon admixture is similar to that of concrete mixed with fly ash and granulated blast furnace slag.7.The production process of composite admixture containing mixing station waste residue was designed,and the key technical points of quality control of composite admixture were proposed from the aspects of raw material optimization,proportion composition,production processing and finished product control.The composite admixture has been successfully applied in the common public construction,civil construction and infrastructure engineering,and has achieved good economic and social benefits.