污泥固化土强度特性研究

为明确污泥固化处理后的强度变化特征,并从水分转化角度揭示其变化机理,对不同水泥添加量和不同养护龄期条件下污泥固化土的强度特性进行了室内试验研究。结果表明:(1)污泥固化土的无侧限抗压强度与水泥添加量呈线性正相关,固化系数k随着养护龄期的增加而增大。0~14 d,k由0.807 9增大到1.251 8,增长幅度较大,为54.94%;14~28 d,k由1.251 8增大到1.488 7,增长幅度明显减小,为18.92%。(2)无侧限抗压强度与养护龄期之间呈现良好的正相关性,二者拟合的相关系数在0.969 8~0.999 7之间。(3)水泥主要与污泥中结合势能较低的自由水发生水化反应,随着水泥添加量的增加,自由水百分量降低明显,下降幅度达到47.7%,结合水百分量降低缓慢,下降幅度仅9%;且水化反应在14 d内基本完成,14 d内水化反应消耗的自由水含量约为28 d内的80%。研究成果可为污泥固化土这种特殊性质土体的基本力学性质研究提供基础参数,为实际固化施工工艺的选择提供了参考。

Study on strength characteristics of solidified sludge

In order to define the strength variation characteristics of solidified sludge and reveal the variation mechanism from moisture transformation, an experimental study was carried out on the solidified sludge samples with various cements added and curing periods. The result shows that ①the unconfined compression strength of solidified sludge is linearly correlated with the amount of cement addition, the curing coefficient k increases with the curing period. In 0~14d, k increases from 0.8079 to 1.2518, a larger growth rate of 54.94%; 14~28d, k increases from 1.2518 to 1.4887, the growth rate decreases significantly to 18.92%. ②The positive correlation between unconfined compressive strength and curing period is good, with fitting correlation coefficient between 0.9698 ~ 0.9997. ③Cement is mainly hydrated with free water of lower potential energy in sludge. The percentage of free water decreases significantly as the added cement increases, reaching 47.7%, while the amount of bound water decreases slowly at rate of only 9%. Moreover, the hydration reaction is basically completed within 14 days. The free water content consumed in hydration reaction within 14 days is approximately 80% of that within 28 days. The research results can provide basic parameters for basic mechanical property study of solidified sludge, providing an important reference for the selection of construction technology in the actual sludge solidification process.