Effect Of Rice Husk Ash/Calcium Acrylate On The Mechanical Performance And The Hydration Process Of Cement

Ordinary Portland cement as one of the most common building materials, in waterconservancy, transportation, industrial facilities, civil construction and other major projects,occupies an important position. However, cement due to the material composition and porestructure of itself, make it easy to corrode in corrosion environment, poor durability, resultingin the collapse of buildings destroyed, bring immeasurable loss. In order to improve thecorrosion resistance and brittleness of cement, effects of rice husk ash/calcium acrylate oncement properties and process of hydration is researched in this topic.Experiment with home-made rice husk ash and calcium acrylate as raw material,orthogonal test and single factor test are used to determine the optimal formula for the higheststrength and corrosion resistance to sulfate. And by measuring the water requirement ofnormal consistency and setting time, hydration heat, infrared spectra, DSC-TG, XRD analysisand so on, effects of rice husk ash/calcium acrylate on hydration process of cement isresearched. Hydration products morphology of modified cement is obersved by SEM. Bymercury injection apparatus test, effects of the rice husk ash/calcium acrylate on porosity andpore diameter size is researched.The result indicates that: through orthogonal test and single factor variable test todetermine the best way to deal with rice husk ash: use3%of dilute hydrochloric acidacidification, combustion temperature is540℃, and holding time is1h, as well as contentofSiO2in rice husk ash is93%under this condition.By orthogonal experiment and single factor variables to determine the compressivestrength and good corrosion resistance under the condition of the optimal solution: rice huskash is15%; calcium acrylate mixed is1%in proportion to the total ash content (rice husk ashand cement); initiator is3%in proportion to calcium acrylate; the crosslinking agent is5%inproportion to calcium acrylate; and the promoter is5%in proportion to calcium acrylate.1dstrength slightly below the blank sample,3d compressive strength is higher than that of blanksample, rice husk ash/calcium acrylate added to cement has a greater influence on the laterstrength,28d compressive strength compared with the blank sample, increased by33.3%;Corrosion resistance coefficient is the highest(1.35) at this time, increased by57%, the compressive strength and corrosion resistance are obviously improved.SEM analysis is carried out on the corrosion sample, F0sample structure of corrosion inNa2SO4solution is found relatively loose; the structure of F3sample is compacted better thanblank sample after corrosion in water and sodium sulfate solution. By analysising porestructure of28d sample, we can know that adding rice husk ash and calcium acrylate canrefine pore structure of cement paste effectively. In water, F3porosity decreases22.2%,porosity of F3sample have a certain degree of refinement than F0sample. Compared withblank sample, number of less than10nm wool stoma increases and harmful holes of greaterthan1100nm decreases, so the aperture is refined. In sodium sulfate solution, total porosity ofF0and F3is55.25%,31.55%, respectively. F3sample decreases23.7%. Compared with F0,the hole of much greater than100nm decreases significantly.Water demand of rice husk ash is bigger. When the dosage of rice husk ash is fixed,water requirement changed little with the increase of calcium acrylate; when the dosage ofcalcium acrylate is fixed, water demand increases with the increase of rice husk ash. Initialsetting time is shortened, and calcium acrylate has a certain impact on the initial setting timeof cement. Through microscopic analysis, rice husk ash/calcium acrylate addition reduces thetotal heat release.1d hydration is inhibited by calcium acrylate, the Ca(OH)2of the modifiedsample of endothermic peak at3d increases obviously than that of1d, and at this time,calcium acrylate no longer suppress the hydration of cement. SiO2start to react with thehydration products Ca(OH)2and produced lower than calcium silicon gel, with ongoinghydration, gel to accumulate.Through SEM analysis, the early hydration were suppressed, hydration products is littleto some extent. At age of3d, we can see the acicular ettringite, and found that the six-partytabular morphology of Ca(OH)2has taken a knock. The active SiO2begin to play a role. fHydration or3d, a large number of fibrous, overlapped C-S-H(Ⅱ) crystals can be foundgrowing in pores or loose region. Hydration for28d, structure is relatively dense, and thehydration products is mainly gel, which is the reason of high strength at late age.As a result, studies have shown that the addition of rice husk ash/calcium acrylate notonly can obviously increase the28d compressive strength, resistance to sulfate erosionperformance is also obviously improved. The addition of rice husk ash/calcium acrylate, not only optimize the distribution of the pore structure of cement paste, and also reduces theharmful pore ratio, increase the proportion of the bore is harmless and less pollution. Ricehusk ash/calcium acrylate is not only improve the performance of the cement, and reducepollution, the environmental protection work.