Research On Performance Optimization Of Specified Density Concrete

Specified density concrete has borad development prospects on tall building,large-span and prefabricated building,et al,due to light and high strength.Specified density concrete widely uses artificial lightweight aggregates and reduces the consumption of natural aggregate,which meets the need of era of green and sustainable development.Therefore,in combination with mechanical properties,durability,surface properties,and process flow of specified density concrete,in-depth study of specified density concrete available in practical engineering has far-reaching significance for the practical application of specified density concrete.In this paper,LC40 specified density concrete is taken as the research object.The effects of the main constituent materials on the apparent density,mechanical properties,impermeability and frost resistance of specified density concrete are studied and the mix proportion and preparing technology of specified density concrete are optimized.Image processing technology is used to quantitatively characterize the surface properties of specified density concrete,and based on the research results,the paper proposed method for improving the surface properties of specified density concrete and summarized the preparing process of grade LC40 specifed density concrete for prefabricated members,the research results can provides technical support for practical application of specified density concrete.Through the individual factor analysis,the paper systematically studied the influence of the main components of specified density concrete on the mechanical properties.The results show that mechanical properties of specified density concrete decline with the increase of ceramsite when the content of ceramsite is 0%-40%of the amount of crushed stone.The pre-wet 24h ceramiste can improve mechanical properties of concrete in late period.When fly ash content is 0%-40%of cementitious material,mechanical properties of concrete improves.When W/B ratio is between 0.26 and 0.36,the mechanical properties becomes better with the increase of W/B.When 5-20 mm particle size gravel and 5-20 mm particle size ceramsite are combined,the mechanical properties of specified density concrete performs well.Combined microscopic testing techniques,the effects of ceramsite content,ceramsite pre-wet degree,water-cement ratio,fly ash content,aggregate grade on the impermeability and freeze-thaw resistence property of specified density concrete were studied.The study shows that the impermeability of specified density concrete declines and its freeze-thaw resistence property improves with the increase of ceramsite,when the content of ceramsite is 0%? 40%of the amount of crushed stone.Pre-wet ceramsite is beneficial to the impermeability and freeze-thaw resistence property of specified density concrete.When fly ash content is 0%?40%of cementitious material,the impermeability and freeze-thaw resistence property of concrete improves.The impermeability improves and the freeze-thaw resistence property become worse with the increase of W/B.When 5?20 mm particle size gravel and 5?20 mm particle size ceramsite are combined,the impermeability and freeze-thaw resistence property of specified density concrete performs well.Based on Image-pro plus image processing technology,this paper studied the effects of defoaming agent,vibrating time,mold,mold release agent and protective agent on the surface performance of specified density concrete.The results suggests that the optimal dosage of defoamer is 2.4%.the optimal time for vibrating is 12?15 s,the performance of specified density concrete surface reach the best when using glued wood mold and salad oil as release agent.The protective agent has a significant effect on reducing the holes diameter of 0?1 mm,while makes little differences to reducing the holes of 1?6 mm.At last,the paper concluded the production process of prefabricated members using specified density concrete from four aspects:raw materials,batching,demold and curing,quality control.The acceptance inspection and re-inspection of raw materials should be strictly in accordance with the specifications,during the production,the designed feeding order and mixing time should be carried out strictly.The members should be inspected after demoulding and curing,and the conformed qualified members are sprayed with protective agent.