Stabilization of black cotton soil subgrade using sawdust ash and lime

This research dwells on how black cotton soil (BCS) could be stabilized and made a suitable subgrade material using sawdust, a readily and cheaply available material. Sawdust was burnt to ashes in a furnace at a temperature of 800?°C and then mixed with BCS in varying proportions of 4%, 8%, 12%, 16% and 20%. Since the trial mixes showed that the use of 16% sawdust ash gave better results, the BCS treated with optimum sawdust ash content of 16% was further stabilized with 2%, 4%, 6%, 8%, and 10% lime. Optimum reduction in liquid limit, differential free swell, plasticity index as well as optimum increase in CBR and specific gravity was achieved when BCS treated with 16% sawdust ash was stabilized with 4% lime. Scanning electron microscope images of the freshly prepared stabilized soil showed the occurrence of flocculation and agglomeration while X-ray diffraction tests on the cured stabilized soils showed the occurrence of pozzolanic reactions. It was thus concluded that treating BCS with sawdust burnt in an appropriate environment and combined with lime enhances its strength. It also offers another way to dispose of sawdust.     

石灰粉煤灰稳定黄土的无侧限抗压强度研究

以石灰粉煤灰稳定黄土为对象,通过标准击实试验、无侧限抗压强度试验,研究养护龄期和石灰粉煤灰掺量对稳定黄土最佳含水率、最大干密度及无侧限抗压强度的影响。结果表明,随石灰粉煤灰掺量的增加,稳定黄土最佳含水率增大,最大干密度减小;石灰粉煤灰掺量一定时,随粉煤灰掺量的增加,最大干密度增大,最佳含水率减小;无侧限抗压强度随养护龄期的增长、石灰粉煤灰掺量的增加而增大。通过对试验数据的拟合回归,建立了稳定黄土无侧限抗压强度与孔隙率、粉煤灰与石灰的比值（F/L）及石灰粉煤灰总体积掺量的关系。     

Geo-environmental application of municipal solid waste incinerator ash stabilized with cement

The behavior of soluble salts contained in the municipal solid waste incinerator (MSWI) ash significantly affects the strength development and hardening reaction when stabilized with cement. The present study focuses on the compaction and strength behavior of mixed specimens of cement and MSWI ash. A series of indices such as unconfined compressive strength, split tensile strength, California bearing ratio (CBR) and pH value was examined. Prior to this, the specimens were cured for 7 d, 14 d, and 28 d. The test results depict that the maximum dry density (MDD) decreases and the optimum moisture content (OMC) increases with the addition of cement. The test results also reveal that the cement increases the strength of the mixed specimens. Thus, the combination of MSWI ash and cement can be used as a lightweight filling material in different structures like embankment and road construction.     

Stabilization of clay soils using lime and effect of pH variations on shear strength parameters

This paper presents the results of geotechnical and mineralogical investigations on lime treated clay soils from Hamedan City, Iran, and effects of pH variations on their shear strength parameters. Initially, lime was added in different percentages and laboratory experiments were conducted after curing times. The results indicate that these soils can be stabilized satisfactorily with the addition of about 7 % lime. Also, investigation of the relationship between lime-treated geotechnical properties and lime percentage and curing time demonstrates high regression coefficients for the proposed relationships. Several laboratory tests were performed on treated and untreated clay soils with lime mixed with pore fluids with different pH values including 3, 5, 7 and 9. The results of shear strength tests indicated that the undrained shear strength parameters for untreated clays increased considerably if the pore fluid had a high pH (pH = 9) or a low pH (pH = 3). It can also be found that for lime-treated soils, maximum cohesion and friction angle values are achieved at pH = 9.     

Limestone ash waste as a substitute for lime in soil improvement for engineering construction

 A by-product of the manufacture of cement at Nkalagu, Nigeria, is the waste material comprising 70% CaO and 30% undecomposed CaCO₃, referred to as limestone ash. The potential of this waste as a substitute for lime in the improvement of the engineering properties of laterite soils for construction purposes has been assessed. The geotechnical properties of lateritic soils when untreated and when treated with varying percentages of limestone ash have been established, including particle size analyses, Atterberg limits, Proctor compaction, California bearing ratio (CBR) and shear strength. The results confirmed those obtained by other workers on the use of lime stabilisation and indicate that limestone ash may form a substitute for lime in soil improvement for engineering construction. Received: 14 November 1997 · Accepted: 16 August 1999     

The role of carbide lime and fly ash blends on the geotechnical properties of clay soils

Carbide lime is a by-product obtained during the manufacturing of acetylene from the reaction of calcium carbide and water. A major portion of carbide lime is dumped in waste deposition areas, creating an environmental problem. Carbide lime and fly ash have possible applications in slope stabilization, subgrade improvement of roads, and soil treatments under shallow foundations. A series of Atterberg limits tests, compaction tests, unconfined compressive strength tests, ultrasonic pulse velocity tests, and wetting–drying tests were performed on carbide lime and fly ash treated clay soils to evaluate the effects of additive content, curing time, strength development, and the effects of wetting and drying. A total of 8% of carbide lime constituted the fixation point, and peak strength was achieved at 12% carbide lime content. A total amount of 25% additive was found as a threshold changing the Atterberg limits. Test results indicated that the strength of the treated soil improved by the existence of carbide lime and fly ash; best performance was observed in 28-day specimens with 10% carbide lime and 20% fly ash content reaching to 8 times larger strength than untreated soil. The failure patterns of the specimens reflected the curing time and wetting–drying effects. Although, the application of wetting–drying cycles deteriorated the treated soil, the presence of carbide lime partially prevented the strength loss. New relationships between normalized strength and curing time depending on carbide lime content were proposed. Furthermore, a linear relationship between the unconfined compressive strength and the ultrasonic pulse velocity of the treated soils was established.

     

Study on lime–fly ash–phosphogypsum binder

In this study a new type of lime–fly ash–phosphogypsum binder was prepared to improve the performances of lime–fly ash binder which was a typical semi-rigid road base material binder in China. The modified lime powder had much higher activity than ordinary quick lime or slaked lime powder, it was the best alkali activator to prepare lime–fly ash–phosphogypsum binder. The optimum formulation of this binder was consisted of 8–12% modified lime, 18–23% phosphogypsum and 65–74% fly ash. The parallel experiments shown that lime–fly ash–phosphogypsum binder had higher strength than ordinary lime, cement, and lime–fly ash stabilized soils road base materials, granular soils stabilized with this binder had higher later strength than that of lime–fly ash or cement stabilizing granular soil, it had higher early strength and steady strength development. The phosphogypsum hastened the pozzuolana reactions between the lime and fly ash, it reacted with lime and fly ash also, this reaction formed some AFt and the formation of AFt brought on a slight expansivity which could compensate the shrinkage of the binder. The pore structure of this binder was finer than that of the lime–fly ash, so the strength and performances of the road base material stabilized with lime–phosphogypsum–fly ash binder was much higher than those of the lime–fly ash road base material.     

An investigation into the effects of lime on compressive and shear strength characteristics of fiber-reinforced clays

To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils.Although lime stabilization increases the compressive strength of soils,it reduces the soil ductility at the same time.Recent research shows that random fiber inclusion modifies the brittleness of soils.In the current research,the effects of lime and polypropylene(PP) fiber additions on such characteristics as compressive and shear strengths,failure strain,secant modulus of elasticity(E_(50)) and shear strength parameters of mixtures were investigated.Kaolinite was treated with 1%,3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm.Samples were prepared at optimum conditions and cured at 35℃ for 1 d,7 d and28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests(UCT and TCT) under cell pressures of 25 kPa,50 kPa and 100 kPa.Results showed that inclusion of random PP fibers to clay-lime mixtures increases both compressive and shear strengths as well as the ductility.Lime content and curing period were found to be the most influential factors.Scanning electron microscopy(SEM) analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface,leading to enhanced shear strength.The more ductile the stabilized and reinforced composition,the less the cracks in roads and waste landfill covers.     

石灰粉煤灰稳定建筑垃圾的路用性能研究

对石灰粉煤灰稳定建筑垃圾混合料的强度、模量、抗冻性能等路用技术性能进行了系统的试验研究,结果表明,其各项技术性能满足现行规范的要求,可以作为各级公路的底基层或基层材料。     

Engineering and microstructure properties of contaminated marine sediments solidified by high content of incinerated sewage sludge ash

Management of incinerated sewage sludge ash(ISSA) and dredged contaminated marine sediments(CMSs) is a great challenge for Hong Kong and other coastal cities due to limited landfilling capacity.The present study investigates the use of high content(20% of sediment by mass) of ISSA in combination with cement/lime for solidification/stabilization(S/S) treatment of CMSs to provide a way to reuse the wastes as construction materials.The results showed that ISSA being a porous material was able to absorb a large amount of water rendering a more efficient solidification process of the marine sediment which normally had a very high water content(～80%).The S/S treatment improved the engineering properties of the sediment,but reduced the workability,especially for the lime-treated samples.Lime can be used to replace ordinary Portland cement(OPC) for better heavy metal immobilization and carbon emission reduction.The hardened sediment samples prepared with 10% of lime and 20% of ISSA could attain a strength of 1.6 MPa after 28 d of curing.In addition,leaching tests confirmed that there was no environmental risk induced by these stabilized materials.The formation of hydrated cementitious compounds including calcium silicate hydrate(C-S-H)/calcium aluminate silicate hydrate(C-A-S-H)/hydrocalumite/calcite was mainly responsible for the strength development in the ISSA/lime-treated sediments.     

Effects of waste material–lime additive mixtures on mechanical properties of granular soils

Granular soil was stabilized using different proportions of silica fume–lime and fly ash–lime and compacted at optimum water content. Compaction, compressive strength and California Bearing Ratio tests were undertaken which confirmed that the use of waste materials and lime mixtures improved the strength properties of the crushed granular soils.     

Utilization of a very high lime fly ash for improvement of Izmir clay

This paper presents an investigation into the stabilization of a soft clay subgrade of a military zone in Izmir, Turkey with a very high lime fly ash. Zero%, 5%, 10%, 15% and 20% (m/m) of the soil was replaced with fly ash. In addition to the control specimen, four different stabilized soil samples were prepared mixing fly ash with soil at optimum water contents determined by standard proctor test. Experiments lasted for 3 months and the unconfined compressive strength and shear strength parameters, cohesion and internal friction angle, were determined after 1, 7, 28 and 90 days. It was found that, inclusion of fly ash improved the properties of the soil. The improvements, appearing with increasing fly-ash content, were attributed to the pozzolanic reaction and pore refinement effect of fly ash as well as its high free-lime content.     

固化疏浚淤泥作路基材料工程特性试验研究

为了探讨粉煤灰和工业矿粉固化疏浚淤泥作路基材料的可行性,通过一系列室内实验研究了不同固化剂配比对固化淤泥击实特性、水稳定性、承载力和抗剪强度的影响。实验结果表明,不同固化剂配比下固化淤泥的最大干密度均超过1.50g/cm3,最优含水率约为20~21%;淤泥固化处理后浸水4d的膨胀率均不超过1.1%,水稳性大幅提升;矿粉含量越高,粉煤灰含量越低,CBR(California Bearing Ratio)值越高,土样的承载力越高,抗剪强度也越高。不同工况浸水4d的CBR值均达到了较高的水平,工况SD10FA20MP(淤泥∶粉煤灰∶矿粉=7∶1∶2)CBR值最高,达到了34.8%,是规范中高速、一级公路路基填料要求最低CBR值的4.35倍,作路基填料使用可行。     

磷石膏基复合胶结料性能研究

通过XRD、SEM微观分析和宏观强度测试手段,探讨了适合作胶凝材料磷石膏颗粒的最大粒径,并对磷石膏-粉煤灰复合胶凝材料的最优配合比、最佳养护条件和凝结硬化机理进行了研究.结果表明,适合做胶凝材料的磷石膏颗粒最大粒径为4.75mm,磷石膏-粉煤灰复合胶凝材料的最优配合比为:m(磷石膏):m(生石灰):m(水泥):m(粉煤灰)=40:15:10:35,最佳养护温度为90℃,养护时间为10h.采用最优配合比90℃蒸汽养护10h后自然养护的7d、28d的抗压强度分别为31.5 MPa、36.0 MPa.     

Geotechnical properties and microstructure of lime-stabilized silt clay

The geotechnical properties and microstructures of lime-stabilized silt clay from Jilin province, China, were studied in detail. Laboratory tests were conducted to evaluate the effects of lime content and curing time on the overall soil properties, including compaction characteristics, Atterberg limits, particle size distribution, pH, stress–strain behavior, peak strength, shear strength parameters, and California bearing ratio (CBR). The stabilized mechanisms of lime in silt clay were examined, and the observed test results were explained based on the results of scanning electron microscropy (SEM) and X-ray diffraction analyses of the specimens. Lime content and curing duration significantly influenced the geotechnical properties and microstructure of the lime-stabilized silt clay specimens. An increase in lime content resulted in increases in compaction water content, liquid limit, plastic limit, sand size-fractions, pH, peak strength, cohesion, internal friction angle, and the CBR, but led to a reduction in the plasticity index, silt fractions, clay fractions, swelling capacity, and water absorption. Also, the addition of lime to silt clay changed this soil type from a ductile to a brittle material. The optimum lime content of the silt clays from Jilin province was determined to be approximately 5–7%. SEM micrographs showed that a white cementitious gel was formed after the addition of lime and that peaks related to smectite, illite, kaolinite, and quartz appeared to be sharper after stabilization with lime and a 90-day period of curing. These results show that the geotechnical properties of lime-stabilized silt clay are affected by the microstructural organization of the silt clay itself.

     

Engineering properties of water/wastewater-treatment sludge modified by hydrated lime,fly ash and loess

The purpose of this research was to present engineering properties of modified sludge from water/wastewater treatment by modifiers such as hydrated lime, loess, and fly ash. The proper mixing ratio was determined to hold the pH of the modified sludge above 12.0 for 2 h. Laboratory tests carried out in this research included particle analysis, compaction and CBR, SEM and X-ray diffraction, unconfined compression test, permeability test, and TCLP test. The main role of lime was to sterilize microorganisms in the sludge. The unconfined strength of the modified sludge by fly ash and loess satisfied the criteria for construction materials, which was above 100 kPa. The permeability of all the mixtures was around 1.0 x 10(-7) cm/s. Extraction tests for hazardous components in modified sludge revealed below the regulated criteria, especially for cadmium, copper, and lead. The present study suggested that the use of lime, fly ash, and loess be an another alternative to modify or stabilize water/wastewater treatment sludge as construction materials in civil engineering.     

Comparison of dried sludge and sludge ash for phosphorus recovery with acidic and alkaline leaching

Nowadays, the recovery of phosphorus has been in the spotlight due to its importance for food security and depleting sources. In this study, phosphorus recovery from dried sewage sludge and sludge ash by acid and alkaline leaching was evaluated. Optimum extraction time and temperature were determined as two hours and ambient temperature. Results showed the superiority of strong acidic conditions for leaching; 75 ml/g with 0.4N HCl and 25 ml/g with 0.6N HCl were determined as optimum conditions to achieve efficient phosphorus dissolution from sludge ash (94.6%) and dried sludge (91.1%), respectively, with the lower heavy metal concentrations. Lower L/S ratio put forward the dried sludge as a more advantageous resource for phosphorus extraction. Besides, by alkaline leaching of sludge ash and dried sludge, 60.3 and 70.3% phosphorus dissolutions were achieved with 75 ml/g and 1N NaOH; and the leachate was a suitable product for phosphorus precipitation due to its high pH.     

The potentials of some stabilizers for the use of lateritic soil in construction

Lateritic soil was stabilized with various percentages of rice husk ash (RHA), lime and cement. Atterberg limits, standard Proctor compaction, unconfined compression and California bearing ratio tests were carried out on lateritic soil with various percentages of these stabilizers in order to examine their influence. The required amounts of ash, lime and cement were determined for economical stabilization. This paper presents the potentials of rice husk ash compared to lime and cement in lateritic soil stabilization. For road construction, it recommends 7% cement for base materials, 5% lime for sub-base materials and 18% rice husk ash for sub-base materials.     

细粒式钢渣改良黄土路基研究

为实现钢渣的全粒度应用及提高利用率,小于等于3mm的细粒式钢渣可作为黄土路基稳定材料使用。设计对照组水泥稳定黄土和石灰稳定黄土,并通过无侧限抗压强度和CBR承载比评价,以确定细粒式钢渣稳定黄土的可行性和最佳掺量。结果表明,随着钢渣掺量增加,钢渣稳定黄土的最大干密度增大,最佳含水率减小。石灰稳定黄土最佳含水率最大,钢渣稳定黄土最小。钢渣稳定黄土的无侧限抗压强度随钢渣掺量增加而增大,10%钢渣掺量的无侧限抗压强度大于3%水泥稳定黄土和6%石灰稳定黄土。水泥稳定黄土CBR承载比远大于钢渣稳定黄土和石灰稳定黄土,且黄土膨胀量最小,最大仅为0.14%,钢渣稳定黄土膨胀性最大,且随钢渣掺量的增大而增大,最大为1.2%。10%钢渣稳定黄土CBR大于6%石灰稳定黄土,10%钢渣膨胀量小于6%石灰稳定黄土,大于7%石灰稳定黄土。10%钢渣掺量可替代6%石灰掺量稳定黄土路基,综合分析选择10%作为最佳细粒径钢渣稳定黄土掺量。     

污泥石灰处理工程中的物料优化管理

介绍了污泥石灰处理的物料优化管理,涉及原始污泥、石灰粉料、处理后出泥以及废气的收集。在此基础上介绍了相关案例,得出以下几个结论值得在工程设计实施中参考:原始污泥含水量过高会增加石灰消耗;污泥石灰处理宜选用粒度小、活性高的粉料;污泥出泥及废气收集方案需根据原始污泥的特点和处理目标的具体情况进行优化设计。