活性稻壳灰改善水泥石灰石粉胶凝材料强度及作用机理研究

Impact of Active Rice Husk Ash on Improvement of the Strength of Cement-Ground Limestone Cementitious Materials and Its Mechanism

研究了稻壳灰(RHA)对水泥石灰石粉浆体强度的改善作用,并通过热重和X射线衍射测定了水泥石灰石粉RHA复合浆体的水化程度及水化产物,分析了相关作用机理.结果表明:复合浆体抗压强度随着RHA掺量的增加先增后降,RHA掺量为10%时,复合浆体抗压强度达到最高,与纯水泥浆体相比,掺入10%RHA和10%石灰石粉的复合浆体3、7、28d抗压强度分别提高了8.21%、18.43%、1.75%,掺入15%RHA有助于提高浆体抗压强度随龄期的增长幅度;RHA具有一定的填充效应、活性效应及内养护作用,掺量小于10%时,RHA填充效应和活性效应起主导作用,能够加速C3S的水化,并进行二次水化反应,提高复合浆体早期抗压强度;RHA掺量增至15%时,因RHA吸附大量水分,降低了水泥的水化程度,导致复合浆体早期抗压强度较低,但随着龄期的增加,RHA逐渐释放吸附水,起到内养护作用,促进水泥水化及参与二次水化反应,从而提高了复合浆体抗压强度的增长.

The improvement of rice husk ash(RHA)on the strength of cement-ground limestone pastes was studied.The hydration degree and products of cement-ground limestone-RHA composite pastes were determined by thermogravimetry and XRD,and the action mechanism was analyzed.The results show that the compressive strength of composite pastes increases at first and then decreases with increasing content of RHA.When RHA content is 10%,the compressive strength of composite pastes is the highest.The compressive strength of 10%RHA and 10%ground limestone composite pastes is 8.21%,18.43%and 1.75%higher than that of pure cement pastes at 3,7,28d,respectively.15%RHA is helpful to the extent of compressive strength increasing with age.RHA has a certain filling effect,activation effect and internal curing effect.When the content is less than 10%,the filling effect and activation effect of RHA play a leading role,which can accelerate the hydration of C3S,and participate in the secondary hydration,and improve the compressive strength of the composite pastes.When RHA content increases to 15%,excessive RHA absorbs a large amount of water,reduces the hydration degree of cement,and leads to the low compressive strength of composite pastes at early ages.The water in RHA is gradually released with the increase of ages.Due to the internal curing effect,RHA promotes the hydration and participates in the secondary hydration of cement.Thus,the compressive strength of pastes is improved.