| Road in forest area is an important transport channel in mountain area,which forms a transportation network in all directions with the bridge and tunnel.In order to build the houses,the forest roads,bridges and tunnels,etc.,a large number of natural sand and gravel aggregate are needed for construction in forest areas such as roads,bridges and houses.If all of them be mined from forest area,the geological and geomorphologic landscape would be destroied.If the building waste could be full used into regeneration of reinforced concrete buildings,structures,from solid waste,such as old reinforced concrete after demolition of cities,towns or villages,it will be a ecological sustainable development path of the protection forest.Based on the survey of the status quo,progress and existing deficiencies of recycled concrete research at home and abroad,studies of tests as well as theoretical analysis in depth and in details were conducted on the fully regenerated reinforced concrete members in close collaboration with projects supported by Hunan Department of Science and Technology,Hunan Construction Department,Guangdong Education Department,Changsha Technology Bureau,Zhuzhou Construction Bureau and Huizhou Urban and Rural Construction Planning Bureau.The paper endeavors to solve problems which the mix proportion design for recycled concrete and the manufacturing fully recycled reinforced concrete beam-column with recycled concrete and recycled steel bar so as to provide valuable research findings for making a maximum use of the recycling of the wasted concrete and the wasted steel bar in the demolition of old buildings in urban and rural areas.The main works and innovating achievements in this paper as follows:The first,waste concrete was past through crushing → screening → grading made of different thickness of recycled coarse and fine aggregate,tested additional water,was put a new method of the mix proportion design forward for fully recycled aggregate concrete,the system of quaternary first order equations or six dimensional system of equations were established for the recycled or fully recycled coarse and fine aggregates,and calculating system of generalized mix ratio equation for mix n mixtures in the recycled or fully recycled concrete,additional water use of practical calculation formula,hereby the quality and strength of recycled or fully recycled aggregate concrete prepared by this new method were roughly the same as that of natural aggregate concrete,even higher than that of ordinary concrete in some fields.The second,24 fully regenerated reinforced concrete(FRRC)and ordinary reinforced concrete(ORC)beam and column members were made,including 12 fully regenerated reinforced concrete beams-columns(FRRCBs)and 12 ordinary reinforced concrete beams and columns(ORCBCs)members.According to the combination forms of 6 different proportions of materials,they were divided into 6 groups.every group of including 2 FRRCBs and 2 ORCBCs were tested and compared respectively.The additives are polycarboxylic acid water reducer,fly ash and granulated blast furnace powder,which were poured and formed respectively.The third,the strain and deformation,crack and failure characteristics of 12 fully regenerated reinforced concrete beam-column members(FRRCBCMs)and 12 ordinary reinforced concrete beam-columns members(ORCBCMs)under different loading conditions were observed,tested and counted for the first time.A series of valuable and meaningful experimental data were obtained.Through in depth and detailed research and analysis,the main results as follows:(1)The quality of fully recycled aggregate concrete made by the new method of the mix proportion design was quite good and its strength was even better than that of ordinary concrete made by natural aggregate.(2)Physical and mechanical tests of reinforced bar(REBAR)were carried out after remediation,straightening and derusting treatment of the abandoned REBAR removed on site.Eligible reinforcement can be used to regenerate concrete components,structures or structural systems.(3)The strength of fully recycled concrete with fly ash plus mixed fly ash and mineral powder were obviously higher than that of ordinary concrete with the same fly ash and mixed fly ash and mineral powder,while the strength of single mixed mineral powder was lower than that of ordinary concrete with the same mineral powder.(4)The failure modes of bending and flexural-shear of fully regenerated reinforced concrete beams were similar to those of ordinary reinforced concrete beams.The rule of strain variation of shear stirrups was increased firstly and then decreases along with the height,but the flexural deflection and ultimate bending moment of the regenerated reinforced concrete beams were larger than that of ordinary beams combined with flexural and shear.Except for the RL-2 beam,flexural-shear composite failure mode of ordinary beams,the abdominal shear oblique main crack of the regenerated reinforced concrete beam was long and flat walnut like,but the crack was a little more and more dense,with larger width and deflection than the ordinary reinforced concrete beam at the same design strength grade,and the development trend of the flexural and shear crack between the two were roughly the same.(5)The conerete strain,steel strain,lateral displacement and damage conditions of fully recycled reinforced concrete column in eccentric compression experiment are similar to that of ordinary reinforced concrete column,but the bearing capacity was larger than ordinary reinforced concrete column. |
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