赤泥对磷石膏生物胶结的充填性能影响研究

Effect of red mud on the filling performance of phosphogypsum bio⁃cement

为了解决充填骨料磷石膏强酸性劣化生物胶结充填体材料性能的问题,提出引入碱性固废赤泥的方法,探究添加不同质量分数的赤泥对磷石膏生物胶结充填料浆和充填体力学性能的影响。结果显示:在微生物诱导碳酸盐沉淀(Microbially Induced Calcite Precipitation, MICP)作用下,充填骨料中赤泥质量分数从0提高至80%时,充填料浆的泌水率由17%增至44%,表观黏度由585 mPa·s降至121 mPa·s,初、终凝时间分别增加了139%和135%。赤泥质量分数影响磷石膏生物胶结充填体的单轴抗压强度(Uniaxial Compressive Strength, UCS)。当赤泥占骨料总质量的20%时,充填体强度最高,为2 070 kPa,而过高的赤泥添加质量分数会导致UCS降低。强度的变化与赤泥的高碱性和干缩性有关。研究为碱性固废赤泥在磷石膏生物胶结充填中的应用提供理论基础和技术支撑,实现了固废资源化利用。

To solve the problem that the strong acidity of the filling aggregate phosphogypsum degrades the material properties of bio⁃cemented backfill,the method of introducing alkaline solid waste red mud was put forward.We studied the effects of different mass fractions of red mud on phosphogypsum bio⁃cemented filling slurry and the mechanical properties of filling.The results show as follows:(1)Due to the properties of low water absorption,small particle size,and difficult settlement of red mud,when the mass fraction of red mud in filling aggregate increased from 0 to 80%under the action of MICP,the bleeding rate of filling slurry increased from 17%to 44%,the apparent viscosity decreased from 585 mPa·s to 121 mPa·s,and the initial and final setting time increased by 139%and 135%,respectively.(2)The content of red mud affects the Uniaxial Compressive Strength(UCS)of backfill.When the red mud accounted for 20%of the total aggregate,the high alkalinity of the red mud could create a suitable alkaline environment for bacteria,inducing more cementation products and increasing the strength of the backfill up to 2070 kPa.However,when the additional mass fraction of red mud in the filling aggregate is too high,UCS of the filling body will decrease.On the one hand,due to the relative reduction of calcium source in the aggregate,calcium carbonate production will decrease;on the other hand,the drying shrinkage of red mud itself will lead to the deformation of the filling body,damage the formed colloidal structure of calcium carbonate,and result in the reduction of compressive strength of filling body.This study provides a theoretical basis and technical support for the application of alkaline solid waste red mud in phosphogypsum bio⁃cemented backfill and realizes the resource utilization of solid waste.