| Sintered clay bricks have been widely used in urban and rural construction as the main building materials.With the development of urbanization and the reconstruction of old urban areas,these brick structures are gradually dismantled,resulting in a large number of discarded sintered clay bricks.The recycling of these clay bricks is of positive significance to environmental protection and raw material consumption.Rational utilization of waste sintered clay bricks in construction waste can reduce carbon emission in urban construction and realize environmental protection and sustainable development.At present,there are many scholars both at home and abroad,on the recycling of construction waste concrete mechanics performance and durability test,the results show that compared with normal concrete,brick and recycled concrete aggregate and adding a large number of brick aggregate,make its have the significantly different compared with the conventional concrete,and brick aggregate research mostly brickbat aggregate situation of low dosage.This paper improved the brickbat aggregate content,the main research will brickbat aggregate with high replacement ratio in mixed into concrete,mechanical properties of recycled concrete is studied,and the mixed brickbat aggregate of recycled concrete,coefficient of thermal conductivity,the influence of reinforcement corrosion performance,discusses the application of recycled concrete brick aggregate and feasibility in the wall materials.The proportion design of recycled concrete is calculated according to C20 ordinary concrete.The recycled concrete specimens with single recycled coarse aggregate,recycled concrete specimens with double recycled coarse aggregate and fine aggregate,and recycled concrete specimens with double recycled coarse aggregate and fly ash are designed step by step.Among them,the dosage of natural aggregate replaced by coarse aggregate of broken brick alone and the dosage of natural aggregate replaced by coarse aggregate of broken brick and fine aggregate of natural aggregate of double are the same three dosage,which are 50%,70% and 100%.The substitution rate of coarse aggregate and fly ash of reclaimed broken brick is 50% and100%,and the substitution amount of fly ash for Portland cement is 40%.The watercement ratio of all recycled concrete specimens is 0.7,and the dosage of waterreducing agent is 0.5%.In view of the high porosity of broken brick aggregate affecting the actual water consumption,two pretreatment methods of pre-soaking and additional water were studied.The test results show that the pretreatment method of additional water is better.In view of the three groups of recycled concrete with different replacement rates adding corresponding extra water consumption respectively,the effects of reclaimed coarse aggregate with single mixed brick,reclaimed coarse aggregate with double mixed brick,reclaimed coarse aggregate with double mixed brick,reclaimed coarse aggregate with fly ash on mechanical properties,thermal conductivity and steel corrosion properties of reclaimed concrete are discussed.At the same time,the life cycle cost of recycled concrete with coarse aggregate of broken brick is analyzed,and the results obtained during the study are as follows:（1）In the compressive strength and flexural strength tests of RCAC,the 28 d compressive strength of RCAC can meet the design requirements and reach C20 strength when the replacement rate of RCAC is 50% and 70%.The 28 d flexural strength of 50%,70% and 100% recycled concrete with the replacement rate of coarse aggregate of broken brick reached C20 strength grade.（2）In the compressive strength and flexural strength tests of coarse and fine aggregate recycled concrete（RCFAC）,the compressive strength and flexural strength of the three groups of recycled concrete all reach C20 strength grade;Compared with ordinary concrete,the 28 d compressive strength of coarse and fine aggregate recycled concrete with double broken brick decreased by 30%,42% and 50%,respectively.（3）In RCAC,fly ash is used to partially replace ordinary Portland cement,and the influence of activator on recycled concrete with fly ash is analyzed.Only fly ash without activator will seriously affect the compressive strength of recycled concrete,especially the early compressive strength;In recycled concrete mixed with sodium silicate and sodium sulfate respectively two exciting agent to study the influence on the strength of the recycled concrete with fly ash,the results showed that sodium silicate is less,to the promotion of recycled concrete strength is less than 5%,sodium sulfate can react with fly ash,the regeneration of the activity of fly ash in concrete,make the recycled concrete early strength enhancement,The 28 d compressive strength of recycled concrete is basically the same as that of ordinary concrete control group.（4）reference to a certain percentage of the preparation of recycled concrete wall panel sample and test its coefficient of thermal conductivity,at the same time,through the finite element software to simulate the thermal conductivity of brick and recycled concrete coarse aggregate board,showed that with the blocks,an increase in the amount of coarse aggregate,the coefficient of thermal conductivity of recycled concrete wallboard is on the decline,the numerical simulation result was consistent with the experimental results.（5）Steel corrosion analysis was conducted on RCAC.Through electrochemical analysis,it was concluded that when 50% coarse aggregate of broken brick was added,recycled concrete had the lowest impedance,the largest corrosion current and the worst corrosion resistance.When 70% aggregate of broken brick was added,the corrosion trend of steel in recycled concrete weakened,and the early corrosion current was lower than that of ordinary concrete.It shows that the corrosion resistance of recycled concrete can be improved when 70% coarse aggregate is added.（6）Through the production cost and environmental cost,the comparative analysis of the life cycle of recycled concrete and ordinary concrete shows that there is no significant difference in the production cost of recycled concrete and ordinary concrete,but in the aspect of environmental protection,its environmental protection cost is significantly lower than ordinary concrete.In this paper,we study the rubble of coarse aggregate maximum dosage of 100%,the recycled aggregate concrete is prepared,but according to a study in this paper,when brickbat aggregate content reached 100% significantly lower mechanical properties,at the same time will brickbat aggregate as coarse and fine aggregate with mechanical properties decrease is more apparent,fly ash and exciting agent to join to the blocks the strength of the recycled concrete aggregate,Therefore,the later stage is of great significance to increase the strength of recycled concrete under the condition of high replacement rate of broken brick aggregate.It is possible to measure the thermal conductivity and steel corrosion of recycled concrete with broken brick aggregate for the use of recycled concrete in building bearing structures.The calculation of life cycle cost of recycled concrete can be helpful for the enterprise production of recycled concrete of broken brick aggregate.Figure : [42];table : [46];reference : [62]... |
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