| With the rapid development of urbanization in China,the generation and storage of domestic waste have increased sharply.Incineration treatment has attracted attention because of its multiple advantages such as resource utilization,volume reduction,and harmlessness.However,incineration also produces a large amount of tailings accumulation,which makes the disposal and utilization of tailings become the research focus in the field of solid waste and environmental protection.Given this,this thesis systematically studies the physicochemical properties of tailings and forms the technological process and strengthening method for preparing tailings light-coarse aggregate,tailings fine-grained aggregate,and tailings powder.The thesis proposes a new way to prepare specified density concrete(SDC)by using tailings lightweight aggregate(TLA),and formed a composition design method for TLA to prepare SDC;studies the effect of tailings lightweight aggregate on the performance,shrinkage,and Influence of Cracking Properties.Based on the mechanical properties of lightweight concrete and the structural analysis of the interfacial transition zone,the stress-strain constitutive model of lightweight concrete was established.The application performance of lightweight concrete with tailing aggregate under cold,drought,and salt environment in northwest China was explored,and the reliability model was established.The research results can provide a theoretical basis for the preparation of SDC,so as to improve the absorption potential of tailings in building materials,which has important practical significance for alleviating the shortage of natural aggregate resources and the problem of garbage siege.The main research conclusions are as follows:(1)The tail residue is in compliance with the requirements for the nature and environmental safety of lightweight aggregate,and is prepared according to the TLA preparation process of"two crushing,four-point selection,four removals of miscellaneous material,and four screening"as well as the roller plastic surgery and level reinforcement enhancement method.Lightweight coarse aggregate of 5 mm and10 mm tailing slag,a lightweight fine aggregate of 150μm,300μm,600μm,1.18 mm,and 2.36 mm tailing slag were prepared,with specific surface areas of 300 m~2/kg,400m~2/kg and 500m~2/kg tailing powder.(2)The specific parameters of SDC material composition design are as follows:the optimal doping of the tail residue was 50%,and the optimal fineness modulus was3.0;the optimal density of light coarse tailings aggregate was 1000,the maximum particle size was 9.5mm,the particle size coefficient was 0.46,the dosage was 50%,and the pre-water absorption was 100%.The best aggregate skeleton combination can be formed by using 10-20mm ordinary coarse aggregate as the strength skeleton and 5-10mm lightweight coarse aggregate of tail slag as the filling body.It is advisable to choose a polycarboxylic acid superplasticizer,vibration stirring,and sand rate of 38%.A calculating SDC additional water volume formula and SDC combined ratio design steps and methods.(3)Compared with ordinary concrete,the plastic viscosity,yield stress,and thixotropy of SDC increased,while the Slump,mobility and gas content all decreased.The layering of the mixture,the layering of the ordinary osteogenesis,and the layering of the TLA have increased,that is,the TLA increases the fluidity of the SDC and reduces the liquidity of the SDC,increaseing the layering of the SDC.Using the method of crushing type preabsorptive TLA,adding water reducing agents,fine aggregates of tailing slag and fine powders of tailing slag,a synergic relationship between TLA,ordinary aggregate,and mortar matrix can be established resulting in a better density synergy.To reduce the relative motion velocity of aggregate particles and improve the fluidity and evenness of SDC,the static three-force equilibrium equation of TLA can be established.(4)The compressive strength,flexural strength,and tensile strength of SDC are smaller than those of ordinary concrete,and the energy absorption capacity of SDC is stronger than that of ordinary concrete.The SDC with a TLA substitution rate of 50%has a higher specific strength,and the microhardness of the TLA interface is larger than that of the ordinary aggregate interface,while the porosity and average pore diameter are smaller than that of the ordinary aggregate interface,respectively.(5)According to the internal and external locking reinforced structure formed by two kinds of aggregate in SDC,the HJC model was modified by introducing the reinforcement coefficient(I_f),and it was found that the error between the numerical simulation results and the experimental results was less than 10%.The HJC model of the modified SDC and the selected model parameters had high reliability in the impact mechanical property analysis of SDC.(5)Considering the competitive synergism between the self-expanding deformation and the self-shrinking deformation of SDC,the capillary negative pressure(p_m),dry apparent density(ρ_c),internal stress(δ_c),and critical pore(r_c)parameters were introduced,and the Zhang Jun-Hou Dongwei self-shrinking correction model was established.The self-shrinking test data were used to verify that the difference between the test results of SDC-25,SDC-50,and SDC-75 relative humidity critical point and the modified predicted contraction values of Zhang Jun-Houdongwei was 2.4%,1.8%,and 1.3%,respectively,and the deviation between the two was within 20%,while the correlation coefficient(R~2)was 0.943.This shows that the modified Zhang Jun-Hou Dongwei model is suitable for SDC self-shrinking prediction of internal maintenance shrinkage type.(7)The time when the corrosion current density of OC,SDC-25,SDC-50,SDC-75,and LWAC reaches the threshold value is 1276h,1127h,874h,and 816h and738h,respectively,indicating that the resistance of SDC to sulfate and chlorine salt erosion is worse than that of ordinary concrete.But the resistance of SDC to sulfate and chlorine salt is better than that of lightweight aggregate concrete.(8)According to the prediction of the Weibull distribution function,the reliability of SDC-25,SDC-50,and SDC-75 reaches 0 when the freeze-thaw cycles are 214,228,and 246 times respectively.When the carbonation erosion time is 137d,146d,and 158d respectively,the reliability is 0.When sulfate attack is 224,176,and174 times respectively,the reliability is 0.Again,the reliability is 0 when the electric acceleration time of chlorine salt corrosion resistance is 847h,651h,and 594h respectively.(9)As a functional environment-friendly concrete,SDC is suitable for use as antifreeze melt and anti-carbonation material instead of ordinary concrete in freeze-thaw and carbonation erosion areas,as well as a reinforcement material for areas where there is sulfate and chlorine salt erosion instead of lightweight aggregate concrete.(10)Among the products offered by SDC are the inner wall panel,the outer wall panel,unburned brick,stone along the road,and enclosures,which are used in buildings of various types,including high-rise buildings,multi-floor buildings,luxury residential buildings,self-built houses,feeding plants,sidewalks,ancient walls,and garden enclosures.Compared to traditional aggregates(machine aggregate,natural aggregate and lightweight aggregate),preparing SDC with TLA costs approximately10%-20%less than preparing ordinary concrete with traditional aggregates. |
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