碱性氧化剂对水泥固化淤泥强度的影响研究

为消除淤泥中有机质对水泥固化淤泥的不利影响,提出了氧化降解有机质、减薄双电层厚度、维持pH值稳定等对策来提高水泥固化淤泥的强度。采用高铁酸钾和碳酸氢钠作为碱性氧化剂,配合水泥对淤泥进行固化处理。通过无侧限抗压强度试验,初步了解碱性氧化剂对水泥固化淤泥强度的影响规律,并利用有机元素试验、动电电位试验、比表面积试验和SEM等手段,进一步探究碱性氧化剂的固化机理。研究结果表明:掺碱性氧化剂的水泥固化淤泥7d无侧限抗压强度达到了1.536 MPa。碳酸氢钠通过中和有机酸,维持水泥固化淤泥为p H=9～10的碱性环境;该条件下,高铁酸钾能高效降解有机质,除去黏土颗粒表面聚合态的有机质胶膜,有利于SiO_2与Al_2O_3游离于孔隙溶液中,促进水泥水化产物的生成。同时,孔隙溶液中游离的高价阳离子与黏土颗粒表面低价阳离子交换吸附,减薄双电层厚度,引起土颗粒的絮凝团聚。

Influences of alkaline oxidant on strength of cement-stabilized sludge

In order to eliminate the adverse effects of organic matter on the treatment of sludge with cement, the countermeasures to increase the strength of cement-stabilized sludge are put forward, including degrading organic matter, reducing thickness of double electric layers and maintaining pH value steadily. The potassium ferrate and sodium bicarbonate are used as the alkaline oxidant to treat the sludge with cement. Through the unconfined compressive strength tests, the influences of alkaline oxidant on the strength of cement-stabilized sludge are understood preliminarily. The solidification mechanism of alkaline oxidant is studied by means of the organic element tests, electrokinetic potential tests, specific surface area tests and SEM. The experimental results show that the unconfined compressive strength of cement-stabilized sludge can reach 1.536 MPa after curing for 7 days using the alkaline oxidant. The sodium bicarbonate maintains the cement-stabilized sludge in an alkaline environment with the pH value at 9 to 10 by neutralizing organic acids. Under this condition, the potassium ferrate can degrade organic matter effectively. Thus, the removal of the organic matter shell on the surface of clay particles is conducive to free SiO₂ and Al₂O₃ to dissolve into the pore solution, which promotes the formation of cement hydration products. Besides, the high valence ions in pore solution replacing the low valence ions on the clay particles surface lead to a decrease in repulsion between the successive diffused double layers and the flocculation of soil particles.