石灰基材料对生土改性效果及机制研究

Study on modification effect and mechanism of lime-based materials on raw soil

针对当前石灰、矿渣、粉煤灰等作为生土改性剂的研究主要是在力学性能及耐久性等宏观性能方面,尝试从上述改性材料对生土改性前后的矿物组成、官能团特征峰、微观结构等微观角度来阐述生土改性的内在作用机制。试验结果表明,(1)单掺石灰时,生土改性效果随石灰掺量增加而提高,最佳掺量为10%,其28 d抗压强度和软化系数分别达到3.69 MPa和0.80,原因是其板状的Ca(OH)_2水化产物填充生土颗粒间的空隙,达到饱和后的Ca(OH)_2仅其骨架作用;(2)当10%石灰分别复掺5%矿渣和5%粉煤灰时,28 d抗压强度分别增长了8.1%和2.4%,软化系数分别达到了0.92和0.90,原因是粉煤灰和矿渣发生二次水化反应,其中Mg—O、Al—O等键断裂,Al^(3+)、Mg^(2+)等阳离子与Ca(OH)_2发生置换反应,致使1 436.47 cm^(-1)处的峰位偏移至1 400 cm^(-1)附近,同时出现了1 030 cm^(-1)附近的C-S-H凝胶特征峰以及3 120 cm^(-1)处左右的火山灰反应特征峰;(3)掺矿渣改性效果优于单掺石灰,而复掺粉煤灰的改性效果不佳。

The current research on the lime,slag,fly ash and other soil modifiers is mainly in the macroscopic properties such as mechanical properties and durability.In this paper,the microscopic angles such as the mineral composition,the functional group peaks and microstructures before and after the modification of the modified materials are attempted to illustrate the intrinsic mechanism of soil modification.The test results show that when the lime was added alone,the modification effect of the raw soil increased with the increase of lime content.The optimum dosage was10%,and the 28 d compressive strength and softening coefficient respectively reached 3.69 MPa and 0.80,because the platy Ca(OH)2 hydration product filled the voids between the raw soil particles,and the saturated Ca(OH)2 only had its skeleton effect.When10%lime was separately doped with 5%slag and 5%fly ash,the compressive strength of 28 d increased by 8.1%and 2.4%respectively,and the softening coefficient reached 0.92 and 0.90 respectively,because the secondary hydration reaction of fly ash and slag occurred,among which Mg-O,Al-O and other bonds were broke.The substitution of cations such as Al^3+and Mg^2+were displaced from Ca(OH)2,causing the peak position at1 436.47 cm^-1 to shift to near1 400 cm^-1,and the CSH gel characteristic peak around1 030 cm^-1 and the characteristic peak of volcanic ash reaction around 3120 cm^-1 appeared.The modification effect of slag-added slag was better than that of single-mixed lime,and the modification effect of complex fly ash was not good.