| Environment is the foundation for the survival and development of mankind,improving the ecological environment,developing green ecological building materials and promoting the construction of sponge cities in line with the national sustainable development strategy.For a long time,a large number of sintered clay bricks in urban and rural areas in our country have been used as load-bearing enclosure materials.In the process of urban renewal and house demolition,large amounts of waste scrap bricks will be produced.The waste brick has certain strength,large porosity and high water absorption.If it is broken,screened,cleaned and reinforced by cement,it can replace the traditional natural coarse aggregate to prepare new recycled brick aggregate pervious concrete.Not only the construction wastes can be recycled harmless resource utilization,saving natural resources,reduce the environmental pollution caused by construction waste on urban and rural areas,solving the problem of shortage of building material resources.But also improve the ecological environment and the way of rainwater utilization,lighten the environmental burden,conducive to soil and water conservation,construct a comfortable living environment for human beings.At the same time,as a kind of environment-friendly material,recycled brick aggregate pervious concrete can be widely used in pavement projects such as pedestrian roads,park communities and water conservancy and civil engineering projects such as embankment revetment and slope protection,which has significant social and ecological benefits.In this paper,the recycled brick aggregate pervious concrete is described in detail,based on the analysis of the development and application of pervious concrete and recycled brick aggregate pervious concrete both at home and abroad,the preparation technology,strengthening method and proportion design of recycled brick aggregate are obtained through experimental research.In view of the shortcomings of recycled brick aggregate pervious concrete,such as low strength and insufficient frost and thaw durability,it is suggested to add admixture and polypropylene steel fiber to improve its performance.On the basis of both strength and pervious performance to determine the best mix ratio,the frost resistance endurance test was carried out to determine the freeze-thaw failure mode and the life prediction model of the concrete.(1)By analyzing the special properties of the scrap brick,the basic physical properties of recycled brick aggregate are measured,such as apparent density,accumulation density,particle size distribution,moisture content,water absorption,crushing index,learn from the treatment of recycled aggregates on the processing and strengthening process at home and abroad,in view of the shortcomings of the waste brick,such as many micro cracks,rough surface,many corners and low strength,the process of preparation and strengthening for recycled brick aggregates is studied.(2)Filling theory and saturated aggregate volume method were used to design the ratio of pervious concrete,draw lessons from pervious concrete preparation process and curing method,in this experiment,the mixing and forming process of split feeding and three-layer intercalation and compacting forming is formed.After molding,together with the mold into the standard maintenance room,the next day mold removal.(3)The mechanical properties and water permeability of recycled brick aggregate pervious concrete were tested by control variables.The results of the control variables show that the water-cement ratio,the target porosity,the aggregate particle size,the polypropylene steel fiber content,the replacement rate of recycled brick have different influences on the strength and water permeability.The optimal mix ratio of mechanical properties and the optimum mix ratio of water permeable performance are taken into account,and the mixture ratio of high strength and reasonable pervious performance is determined.The research shows that when the water-cement ratio is 0.30~0.34,the target porosity is 22%~26%,and the polypropylene steel fiber content is(3~5)kg/m~3,the concrete has good water permeability.The polypropylene steel fiber crack resistance is the most significant and the strength is higher.(4)Based on reasonable water permeable performance and certain compressive strength,the standard specimen of concrete freezing-thawing test was made.The variation law of the elastic modulus loss with freeze-thaw cycle times,mass loss with freeze-thaw cycles of the concrete under freeze-thaw cycle were plotted and reveal the degradation mechanism of service performance of this concrete under the action of freeze-thaw cycles.Using the experiment combined with the mathematical model of the forecasting method,under the single factor of freeze-thaw,the relative dynamic elastic modulus is used to express the evolution equation and mode of freeze-thaw damage of pervious concrete.(5)On the basis of experimental study of permeability,mechanical properties and frost resistance performance,comprehensively analysis the strength,water permeability and frost resistance of the relationship between the three of this concrete,with the goal of the balance of the three,the mix ratio of recycled brick aggregate concrete is determined with high strength,reasonable permeability and good frost resistance.To guide and improve the recycled brick aggregate pervious concrete mix proportion design and production process to be applied to the actual engineering requirements. |
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