Optimization Of Mix Ratio And Reinforcement Performance Of Foamed Concrete With Straw Fiber

With the requirements of building a resource-conserving society,the introduction of national energy saving and consumption reduction polices,high efficient energy construction materials have become the new trend of new construction materials.Foamed concrete is a new energy-saving and fireproof construction material.There are many advantages,such as lightweight,heat preservation,energy saving,waste recycling,safety and environmental protection.However,There are also some of defects,such as shrinkage,cracking,etc.Therefore,the optimization of the mix ratio and reinforcement performance of the foamed concrete with straw fiber is investigated.Comparing the pretreatment of different size of fiber with NaOH solution with different mass fraction,it is found that none-pretreatment fiber and NaOH pretreat fiber have negative influence on regular concrete while the fine fiber being pretreated with NaOH could improve the qualities of regular concrete.The best pretreatment method is developed.The straw fiber with 2~10mm length is soaked in 4%NaOH solution for18h.Then the adhesive solution on the surface of the straw fiber is pressed to be dry.In this way,the modified straw fiber is obtained.The water-material ratio,coal ash,foaming agent,and the amount of straw fiber is investigated to produce a better quality fiber foamed concrete.The results have shown that the compressive strength and dry density of the foamed concrete are inversely proportional to the content of coal ash,foaming agent,and straw fiber.While the water absorption of foamed concrete is proportional to the content of coal ash,foaming agent and straw fiber.In order to determine the best value of those factors,L9(3~4)orthogonal tests are carried out on A07 foamed concrete.As a result,the order of the effect factors on the dry density of foamed concrete is fly ash,water-material ratio,foaming agent,fiber content.For factors'effect on compressive strength of foamed concrete,the sequence is fly ash,water-material ratio,fiber content,foaming agent;For factors'effect on water absorption of foamed concrete,the sequence is fiber content,water-material ratio,foaming agent and fly ash.In order to ascertain the straw fiber reinforced foamed concrete mix ratio,9 test groups are prepared with different ratio of water,fly ash,foaming agent,and straw fiber.Among of them,the contents of water-material ratio take values of 0.35,0.45,0.55.The contents of fly ash take values of 20%,25%and 30%.The contents of foaming agent take values of 1%,2%,3%.And the contents of straw fiber take values of 0.5%,0.75%and 1%.By testing the compressive strength,dry density,water absorption,and thermal conductivity of foamed concrete under different mix ratios,it is concluded that the best mix ratio of fiber reinforced foamed concrete is water-material ratio of 0.35,fly ash of20%,foaming agent of 2%,and straw fiber of 1%.The straw fiber reinforced foamed concrete is made based on the best mix ratio.Its compressive strength,dry density,water absorption and thermal conductivity respectively are 3.7MPa,694 kg/m~3,24%,and 0.16 W/m·K.The values meet the Foamed Concrete standard of China(JG/T 266-2011).It is indicated that the straw fiber reinforced foamed concrete has excellent mechanical and thermal property.