碱性氧化剂对水泥固化淤泥强度的影响研究
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摘要
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。
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 Al2 O3 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.
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 Al2 O3 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.
引文
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[25]崔德山,项伟,曹李靖,等.ISS减小红色黏土结合水膜的试验研究[J].岩土工程学报,2010,32(6):944-949.(CUI De-shan,XIANG Wei,CAO Li-jing,et al.Experimental study on reducing thickness of adsorbed water layer for red clay particles treated by ionic soil stabilizer[J].Chinese Journal of Geotechnical Engineering,2010,32(6):944-949.(in Chinese))
[2]BANOUNE B,MELBOUCI B,ROSQUO?T F,et al.Treatment of river sediments by hydraulic binders for valorization in road construction[J].Bulletin of Engineering Geology&the Environment,2016,75(4):1-13.
[3]陈慧娥,王清.有机质对水泥加固软土效果的影响[J].岩石力学与工程学报,2005,24(增刊2):5816-5821.(CHEN Hui-e,WANG Qing.Influences of organic matter on the effects of consolidating soft soil with cement[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(S2):5816-5821.(in Chinese))
[4]CHEN Hui-e,WANG Qing.The behaviour of organic matter in the process of soft soil stabilization using cement[J].Bulletin of Engineering Geology&the Environment,2006,65(4):445-448.
[5]TREMBLAY H,DUCHESNE J,LOCAT J,et al.Influence of the nature of organic compounds on fine soil stabilizatio[J].Canadian Geotechnical Journal,2002,39(3):535-546.
[6]谷任国,房营光.有机质对软土流变性质影响的试验研究[J].土木工程学报,2009(1):101-106.(GU Reng-guo,FANG Ying-guang.Experimental study of the effects of organic matter on the rheological characteristics of soft soils[J].China Civil Engineering Journal,2009(1):101-106.(in Chinese))
[7]OLIVEIRA P J V,CORREIA A A S,GARCIA M R.Effect of organic matter content and curing conditions on the creep behavior of an artificially stabilized soil[J].Journal of Materials in Civil Engineering,2014,24(7):868-875.
[8]郭印,徐日庆,邵允铖.淤泥质土的固化机理研究[J].浙江大学学报(工学版),2008,42(6):1071-1075.(GUO Yin,XU Ri-qing,SHAO Yun-cheng.Study on mechanism of muddy soil stabilization[J].Journal of Zhejiang University(Engineering Science),2008,42(6):1071-1075.(in Chinese))
[9]TASTAN E O,EDIL T B,BENSON C H,et al.Stabilization of organic soils with fly ash[J].Journal of Geotechnical&Geoenvironmental Engineering,2011,137(9):819-833.
[10]SL237-1999土工试验规程[S].1999.(SL237-1999Geotechnical test procedures[S].1999.(in Chinese))
[11]罗志勇,李和平,郑泽根.高铁酸钾的合成及其在水处理中的应用[J].土木建筑与环境工程,2002,24(6):39-43.(LUO Zhi-yong,LI He-ping,ZHENG Ze-gen.Preparation of potassium ferrate(VI)and its application in water treatment[J].Journal of Civil Architectural and Environmental Engineering,2002,24(6):39-43.(in Chinese))
[12]曲久辉,林谡,田宝珍,等.高铁酸盐氧化絮凝去除水中腐殖质的研究[J].环境科学学报,1999,19(5):510-514.(QU Jiu-hui,LIN Su,TIAN Bao-zhen,et al.Removal of fulvic acid from drinking water using ferrate[J].Acta Scientiae Circumstantiae,1999,19(5):510-514.(in Chinese))
[13]JGJ/T 233-2011水泥配合比设计规程[S].2011.(JGJ/T233-2011 Specification for mix proportion design of cement soil[S].2011.(in Chinese))
[14]CTJ/T 3073-1998土壤固化剂[S].1998.(CJ/T 3073-1998 Soil stabilizer[S].1998.(in Chinese))
[15]熊田恭一.土壤有机质的化学[M].北京:科学出版社,1984.(KUMADA K.Chemistry of soil organic matter[M].Beijing:Science Press,1984.(in Chinese))
[16]窦森.土壤有机质[M].北京:科学出版社,2010.(DOU Sen.Soil organic matter[M].Beijing:Science Press,2010.(in Chinese))
[17]李学垣.土壤化学[M].北京:高等教育出版社,2001.(LIXue-yuan.Soil chemsitry[M].Beijing:Higher Education Press,2001.(in Chinese))
[18]罗志勇,郑泽根,张胜涛.高铁酸盐氧化降解水中苯酚的动力学及机理研究[J].环境工程学报,2009,3(8):1375-1378.(LUO Zhi-yong,ZHENG Ze-gen,ZHANG Sheng-tao.Kinetics and mechanism of the degradation of phenol by ferrate[J].Chinese Journal of Environmental Engineering,2009,3(8):1375-1378.(in Chinese))
[19]DELAUDE L,LASZLO P.A novel oxidizing reagent based on potassium ferrate[J].Journal of Organic Chemistry.1996,61(18):6360-6370.
[20]BOARDMAN D I,GLENDINNING S,ROGERS C D F.Development of stabilisation and solidification in lime-clay mixes[J].Géotechnique,2001,51(5):533-544.
[21]SHARMA V K.Potassium ferrate(VI):An environmentally friendly oxidant[J].Advances in Environmental Research,2002,6(2):143-156.
[22]刘清秉,项伟,崔德山,等.离子土固化剂改良膨胀土的机理研究[J].岩土工程学报,2011,33(4):648-654.(LIU Qing-bing,XIANG Wei,CUI De-shan,et al.Mechanism of expansive soil improved by ionic soil stabilizer[J].Chinese Journal of Geotechnical Engineering,2011,33(4):648-654.(in Chinese))
[23]SPOSITO G.The surface chemistry of soils[M].New York:Oxford University Press,1984.
[24]卢雪松,项伟.离子土壤固化剂加固红色黏土的比表面积研究[J].人民长江,2011(1):83-86.(LU Xu-song,XIANG Wei.Experimental study on specific surface srea of red clay strengthened by ISS[J].Yangtze River,2011(1):83-86.(in Chinese))
[25]崔德山,项伟,曹李靖,等.ISS减小红色黏土结合水膜的试验研究[J].岩土工程学报,2010,32(6):944-949.(CUI De-shan,XIANG Wei,CAO Li-jing,et al.Experimental study on reducing thickness of adsorbed water layer for red clay particles treated by ionic soil stabilizer[J].Chinese Journal of Geotechnical Engineering,2010,32(6):944-949.(in Chinese))
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