Prepartion And Properties Of Cement-based Materials Incorporating Rice Husk And Straw Fibers

Rice husk/Rice straw is a series of agricultural waste, which takes up the cultivatedland and contaminates the environment. Its application in building materials industrywill bring huge economic and environmental benefits. This paper will focus on a kind ofcement-based material used as new light-weight wall materials by applying rice husk,stone flocks, fly ash and a certain amount of cement.The main research contents are that the effects of the dosage of rice husk,pretreatment methods, manufacture technology on the physical and mechanicalperformance and durability of Cement-based Rice Husk Materials (referred to CRHM),and the performance and preparation of Cement-based Straw Fibers Materials(referredto CSFM), as well as the optimization design of CRHW.The experimental results showed that with the dosage of rice husk increased from0to8%, the compressive strength of CRHM reduced88.6%and the volume densitydecreased33.5%. The better mix proportion was with of4%rice husk content, and itscompressive strength at28d reached12.7MPa with the volume density of1617.5kg/m~3.Along with the increase of the rice husk dosage, the mass loss and strength loss ofCRHM were getting bigger after freeze-thaw cycles. The largest mass loss was4.8%and the biggest strength loss was27.5%after50freeze-thaw cycles. The frost resistancegrade of CRHM with of8%rice husk was D25, and the others were D50. The shrinkagerate of reduced with the rice husk dosage increased. At28d, the shrinkage rate of theCRHM without rice husk was467micro strain and the CRHM with rice husk of8%was only220micro strain. The carbonation resistance of CRHM was getting weakerwith the increase of rice husk dosage, because the looser porous structure of CRHM.For example, the carbonation depth with8%of rice husk in14d had reached100mm.The softening coefficient of CRHM gradually decreased with the dosage of rice huskincreased, but all of them were more than0.75. Especially, the softening coefficientCRHM with3%rice husk reached0.95.Compared5kinds of rice pretreatment method,"surface water spray,12h" was thebest way to improve compressive strength of CRHM and "spray organic silane solution,60℃drying" was the best way to improve frost resistance of CRHM.Keep the water cement ratio equaled0.5, the cement base straw fiber materialswere difficult to set and harden when the straw fiber content was more than5%(of thequality of the cement). Of three pretreatment methods for straw fibers, the NaOHsolution processing was the best way to improve the compressive strength of CSFM.When the content of rice husk and straw fiber kept constant, the rice husk could easilyreduce volume density and improve the compressive strength. Even both the volume density showed a little difference, however, the compressive strength of the biggestdifference was5.8times.The sulphoaluminate cement increased the strength of CRHM quickly, whosestrength at1d can reach87%of the28d strength, but it is not suitable for steam curingbecause the3d strength for steam curing is smaller33.8%than that of standard curing at28d. Steam curing was better for the strength growth of CRHM with ordinary Portlandcement. Sand may substitute the crumbs for the production of CRHM. Replaced stonechips made by coal gangue CRHM, the volume density will increases by6.4%and thecompressive strength will increase by30.0%.After the factory testing, according to GB/T15229-2002"Standard for smallhollow blocks of lightweight aggregate concrete ", the rice husk/straw fiber cement basematerials can produce the hollow blocks with volume density level of800~900grade,compressive strength of MU5.0.