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1.
The production and utilization of coal is based on well-proven and widely used technologies. Fly ash, a coal combustion byproduct,
has potential to produce a composite material with controlled and superior properties. The major challenges with the production
of fly ash are in its huge land coverage, adverse impact on environment etc. It puts pressure on the available land particularly
in a densely populated country like India. In India the ash utilization percentage has not been very encouraging in spite
of many attempts. Stabilization of fly ash is one of the methods to transfer the waste material into a safe construction material.
This investigation is a step in that direction. This paper presents the results of an investigation on compressive strength
and bearing ratio characteristics of surface coal mine overburden material and fly ash mixes stabilized with lime for coal
mine haul road construction. Tests were performed with different percentages of lime (2, 3, 6 and 9%). The effects of lime
content and curing period on the bearing ratio and tensile strength characteristics of the stabilized overburden and fly ash
mixes are highlighted. Unconfined compressive strength test results cured for 7, 28 and 56 days are presented to develop correlation
between different tensile strengths and unconfined compressive strength. Empirical models are developed to estimate bearing
ratio and tensile strength of mine overburden–fly ash–quick lime mixtures from unconfined compressive strength test results. 相似文献
2.
工业废渣加固土强度特性 总被引：3，自引：0，他引：3
工业废渣的资源化是解决工业废渣环境污染的有效途径之一。以粉煤灰和高炉矿渣为固化剂,石灰为碱性激发剂,对黏土进行加固。通过室内试验的方法,分析固化剂掺入量、养护龄期等对固化土无侧限抗压强度、pH值和饱和度等发展规律的影响。试验结果表明,固化土的无侧限抗压强度随固化剂掺入量的增加而增大,随养护龄期的增加而增大,提出一个综合反映固化剂掺入量、养护龄期和压实度等因素对固化土强度影响规律的综合影响因子,固化土强度与综合影响因子呈负指数函数关系;粉煤灰+石灰和高炉矿渣+石灰可有效改良土体无侧限抗压强度特性;石灰是一种有效的碱性激发剂,可提供工业废渣发生火山灰反应的高碱性环境。试验成果为工业废渣改良不良土质的设计提供试验依据。 相似文献
3.
粉煤灰与生石灰加固软土的室内试验研究 总被引：20，自引：5，他引：15
粉煤灰是一种工业废弃物,与生石灰一样均可用来加固软土地基。笔者进行了粉煤灰与生石灰加固土的室内配方试验,分别将水泥或生石灰与粉煤灰按照不同的比例干拌均匀后,再与不同含水量的软土人工拌和均匀,测定了不同龄期的无侧限抗压强度;分析了石灰加固土强度与生石灰掺入比和龄期的关系及其压缩系数、压缩模量等的变化。并进一步分析了粉煤灰的加固机理,旨在为其进一步的研究和工程应用提供参考。 相似文献
4.
Physical and engineering properties of soil are improved with various binders and binder combinations. Fly ash and lime are commonly used to improve the properties of expansive soils. An attempt has been made, in this paper, to examine the role of gypsum on the physical and strength behaviour of fly ash-lime stabilized soil. The change in strength behaviour is studied at different curing periods up to 90 days, and the mechanism is elucidated through pH, mineralogical, microstructural and chemical composition study. The strength of soil-fly ash mixture has improved marginally with the addition of lime up to 4 % lime and with curing period for 28 day. Significant increase in strength has been observed with 6 % lime and enhanced significantly after curing for 90 days. The variations in the strength of soil with curing period is due to cation exchange and flocculation initially, and binding of particles with cementitious compounds formed after curing. With addition of 1 % gypsum to soil-fly ash-lime, the strength gain is accelerated as seen at 14 day curing. The accelerated strength early is due to formation of compacted structure with growth of ettringite needles within voids. However, strength at curing for 28 day has been declined due to annoyance of clay matrix with the increase in size of ettringite needle; and again increased after curing for 90 days. The rearrangement of clay matrix and suppression of sulphate effects with formation of cementitious compounds are observed and found to be the main responsible factors for strength recovered. 相似文献
5.
Deformation modulus of fly ash is one of the most important mechanical properties generally used in different design problems
and also as an input parameter to sophisticated numerical techniques employed to assess the response of different structures
resting on fly ash fill or embankment made of fly ash. Deformation modulus is usually expressed in terms of compressive strength.
This paper presents the deformation modulus of fly ash modified with lime alone or in combination with gypsum at different
strain levels. The values of deformation modulus obtained from both unconfined compression test and unconsolidated undrained
triaxial test results are presented herein. The specimens for unconfined compression test and for undrained triaxial tests
were cured up to 90 and 28 days, respectively. The effects of addition of lime (4–10%) and gypsum (0.5 and 1.0%) on the deformation
modulus of class F fly ash are highlighted. With addition of lime and gypsum, the class F fly ash achieved the deformation
modulus in the range of 190 MPa in UCS test and up to 300 MPa in triaxial test specimens tested under all round pressure of
0.4 MPa. Based on the present test results empirical relationships are developed to estimate deformation modulus of modified
fly ash from unconfined compressive strength and relationships between initial tangent modulus and secant modulus at different
strain levels are also developed. 相似文献
6.
Douglas Mohn Teresa J. Cutright John Senko Ala Abbas 《Geotechnical and Geological Engineering》2016,34(1):285-296
The occurrence of sulfate-induced heave of roadways that were chemically stabilized with either lime or cement can require expensive road repairs. Previous research attributed the heave to the formation of an expansive mineral named ettringite. However, not all chemically stabilized soils will exhibit heave. The overall goal of this research was to determine if the sulfate concentration in water can contribute to, or even cause, sulfate induced heave. Two soils, one with a soluble sulfate level below 3000 mg/kg and one with >8000 mg/kg sulfate, were stabilized with either lime or cement and subjected to a capillary soak with distilled water or saturated sulfate water. The low sulfate soils did not swell above the accepted limit of 1.5 %. The high sulfate soils swelled significantly (p < 0.05) above accepted level regardless of the stabilizer used. Overall, stabilized soils subjected to a capillary soak with saturated sulfate water swelled more than soils soaked with distilled water. The results found in this study demonstrated that cement will increase the axial load capacity of the soil, but the soil will still have the potential to heave excessively if sulfate and aluminum are present above the stoichiometric requirements to from ettringite. 相似文献
7.
Hydraulic Conductivity of Fly Ash-Amended Mine Tailings 总被引：1，自引：1，他引：0
Sultan A. Alhomair Mohammad H. Gorakhki Christopher A. Bareither 《Geotechnical and Geological Engineering》2017,35(1):243-261
The objective of this study was to evaluate the effect of fly ash addition on hydraulic conductivity (k) of mine tailings. Mine tailings used in this study were categorized as synthetic tailings and natural tailings; two synthetic tailings were developed via blending commercially-available soils and natural tailings were collected from a garnet mine located in the U.S. Two fly ashes were used that had sufficient calcium oxide (CaO) content (17 and 18.9 %) to generate pozzolanic activity. Hydraulic conductivity was measured on pure tailings and fly ash-amended tailings in flexible-wall permeameters. Fly ash was added to mine tailings to constitute 10 % dry mass of the mixture, and specimens were cured for 7 and 28 days. The influence of fly ash-amendment on k of mine tailings was attributed to (1) molding water content and (2) plasticity of the mine tailings. Tailings that classified as low-plasticity silts with clay contents less than 15 % exhibited a decrease in k when amended with fly ash and prepared wet of optimum water content (w opt ). Tailings that classified as low-plasticity clay exhibited a one-order magnitude increase in k with addition of fly ash for materials prepared dry or near w opt . The decrease in k for silty tailings was attributed to formation of cementitious bonds that obstructed flow paths, whereas the increase in k for clayey tailings was attributed to agglomeration of clay particles and an overall increase in average pore size. The results also indicated that the effect of curing time on k is more pronounced during the early stages of curing (≤7 days), as there was negligible difference between k for 7 and 28-days cured specimens. 相似文献
8.
The potential to use the alkaline residue products fly ash, green liquor dregs, and lime mud originating from paper mills as dry cover materials to seal tailings has been investigated. Metals concentration in lime mud and fly ash had the lowest and highest contents, respectively. The tailings (<1 % sulfur content, primarily pyrite) were disposed about 50 years ago and originated from the former Rönnskär mine site in Sweden. The results of chemical composition analysis show that the raw unoxidized tailings are active toward oxidation, while the components of the adjacent oxidized tailings are not. To quantify the release of metals from the tailings and to evaluate the effect of a sealing layer on oxidation and weathering of the tailings, batch leaching tests were conducted in which leachate from alkaline residue materials was fed to the tailings. The results show that a higher concentration of most trace elements is leached from the unoxidized tailings than from the oxidized tailings. Except As and Cr, the rest of analyzed metals (Cd, Cu, Ni, Pb) became immobilized in response to the increased pH as a consequence of the amendment. The three tested alkaline amendments show a similar potential for preventing the release of metals (with the exception of As and Cr) from the tailings. Under either aerobic or anaerobic conditions, microbial activity was found to be of minor importance. XRD analysis of the field samples revealed that it was feasible to use alkaline residue products in covering tailings, and that it was advantageous to use ash as a cover material more than dregs. 相似文献
9.
电阻率法评价膨胀土改良的物化过程 总被引：4，自引：1，他引：3
掺石灰、粉煤灰是工程中通常采用的改良膨胀土的方法。土电阻率是土的基本物理指标之一,其变化可反映土的其他物理性质指标的变化。通过掺灰改良膨胀土不同养护龄期下的电阻率测试以及膨胀量、膨胀力及无侧限抗压强度等试验研究,探讨了掺灰改良膨胀土养护过程中的物理化学反应过程。根据养护过程中的电阻率随龄期的变化规律,可将改良膨胀土的物理化学反应过程划分为瞬时反应阶段、主体反应阶段、残余反应阶段和稳定阶段4个不同阶段。针对改良膨胀土质量控制和评价体系中存在的不足,提出了基于电阻率指标的改性膨胀土的质量评价方法,通过试验证实了该方法的有效性和实用性。 相似文献
10.
Utilization of fly ash for stabilization/solidification of heavy metal contaminated soils 总被引：19，自引：0，他引：19
Pozzolanic-based stabilization/solidification (S/S) is an effective, yet economic remediation technology to immobilize heavy metals in contaminated soils and sludges. In the present study, fly ash waste materials were used along with quicklime (CaO) to immobilize lead, trivalent and hexavalent chromium present in artificially contaminated clayey sand soils. The degree of heavy metal immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as controlled extraction experiments. These leaching test results along with X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray (SEM–EDX) analyses were also implemented to elucidate the mechanisms responsible for immobilization of the heavy metals under study. Finally, the reusability of the stabilized waste forms in construction applications was also investigated by performing unconfined compressive strength and swell tests. The experimental results suggest that the controlling mechanism for both lead and hexavalent chromium immobilization is surface adsorption, whereas for trivalent chromium it is hydroxide precipitation. Addition of quicklime and fly ash to the contaminated soils effectively reduced heavy metal leachability well below the nonhazardous regulatory limits. Overall, fly ash addition increases the immobilization pH region for all heavy metals tested, and significantly improves the stress-strain properties of the treated solids, thus allowing their reuse as readily available construction materials. The only potential problem associated with this quicklime–fly ash treatment is the excessive formation of the pozzolanic product ettringite in the presence of sulfates. Ettringite, when brought in contact with water, may cause significant swelling and subsequent deterioration of the stabilized matrix. Addition of minimum amounts of barium hydroxide was shown to effectively eliminate ettringite formation. Overall, due to the presence of very high levels of heavy metal contamination along with sulfates in the solid matrices under study, the results presented herein can be applied to the management of incinerator and coal fly ash, boiler slag and flue gas desulfurization wastes. 相似文献
11.
12.
采用核磁共振技术,对不同配比的水玻璃、石灰+粉煤灰及石灰+粉煤灰+水玻璃的固化盐渍土的微观特征进行检测,结合无侧限抗压强度试验,分析了各固化方案的盐渍土固化效果,讨论了强度成因的微观特征机制。结果表明,不同固化土的孔隙特征有较大差异。石灰+粉煤灰固化盐渍土大孔隙减少;石灰+粉煤灰+水玻璃固化盐渍土孔隙总体积减少,但同时有大孔隙生成;水玻璃固化盐渍土孔隙总体增多,但随水玻璃浓度增大,孔隙体积有所减小。石灰+粉煤灰+水玻璃固化盐渍土抗压强度远大于其他固化方案,但是其孔隙结构并不是最优,说明颗粒间的胶结情况对固化效果的影响远大于孔隙特征。 相似文献
13.
《Geomechanics and Geoengineering》2013,8(2):175-181
Expansive soils swell on absorbing water and shrink on evaporation thereof. Because of this alternate swelling and shrinkage, civil engineering structures founded in them are severely damaged. For counteracting the problems of expansive soils, different innovative techniques were suggested. Stabilization of expansive clays with various additives has also met with considerable success. This paper presents, by comparison, the effect of lime and fly ash on free swell index (FSI), swell potential, swelling pressure, coefficient of consolidation, compression index, secondary consolidation characteristics and shear strength. Lime content (weight of lime/weight of dry soil) was varied as 0%, 2%, 4%?and 6%?and fly ash content (weight of fly ash/weight of dry soil) as 0%, 10%?and 20%. A fly ash content of 20%?showed significant reduction in swell potential, swelling pressure, compression index and secondary consolidation characteristics and resulted in increase in maximum dry density and shear strength. Swell potential and swelling pressure decreased with increase in lime content also. Further, consolidation characteristics improved. Compaction characteristics and unconfined compression strength improved at 4%?lime and reduced at 6%?lime. 相似文献
14.
粉煤灰基地聚物作为一种低碳胶凝材料,在地基处理中的应用越来越受到关注。但是目前关于碱激发胶凝材料加固土在冻融极端气候条件下的工程特性尚不清楚,有必要进一步开展冻融循环条件下加固土的强度、变形特征及其影响因素研究。通过室内试验研究了原材料硅铝比、碱激发剂模数及碱溶液浓度对粉煤灰基地聚物固化土的强度与抗冻融性能的影响及微观... 相似文献
15.
P.V. Sivapullaiah J.P. Prashanth A. Sridharan B.V. Narayana 《Geotechnical and Geological Engineering》1998,16(3):239-250
The use of fly ash in geotechnical engineering depends greatly on its pozzolanic reactivity. Though many factors influence the reactivity of fly ash it is well recognized that reactive silica and lime content play a major role. A new, accurate and reliable method for the determination of reactive silica content of fly ash has been established. The reactive silica content, obtained as acid soluble silica in about 2 to 3 N hydrochloric acid, is found to correlate well with unconfined compressive strength of fly ashes. The reactive silica content of fly ash is also important in the stabilization of soils using fly ash. © Rapid Science Ltd. 1998 相似文献
16.
Effect of the combination of lime and natural pozzolana on the compaction and strength of soft clayey soils: a preliminary study 总被引：1，自引：0，他引：1
Soft soil stabilization has been practised for quite some time by mixing additives, such as cement, lime and fly ash to the soil to increase its strength. However, there is a lack of investigations on the use of natural pozzolana alone or combined with lime for ground improvement applications. An experimental programme was undertaken to study the effect of using lime, natural pozzolana or a combination of both on the geotechnical characteristics of soft soils. Lime or natural pozzolana was added to soft soils at ranges of 0?C10% and 0?C20%, respectively. In addition, combinations of lime?Cnatural pozzolana were added to soft soils at the same ranges. Test specimens were subjected to compaction tests, shear tests and unconfined compression tests. Specimens were cured for 1, 7, 28 and 90?days, after which they were tested for unconfined compression tests. Based on the favourable results obtained, it can be concluded that the soft soils can be successfully stabilized by the combined action of lime and natural pozzolana. Since natural pozzolana is much cheaper than lime, the addition of natural pozzolana in lime?Csoil mix may particularly become attractive and can result in cost reduction of construction. 相似文献
17.
Binod Singhi Aminul Islam Laskar Mokaddes Ali Ahmed 《Geotechnical and Geological Engineering》2017,35(5):1907-1920
Clayey subgrade soil requires treatment in order to make the subgrade stable for pavement structures. Treatment of clayey soil i.e. stabilization of clayey soil by cement, lime, and fly ash are established techniques used in geotechnical and highway engineering. Stabilization by alkali activation of fly ash is reported recently but literatures are limited. Present study investigates the stress strain behavior, peak stress and ultimate strain of clayey soil stabilized by slag and slag-fly ash blending by alkali activation. The peak stress as high as 25.0 N/mm2 may be obtained at 50% slags content when 12 molar sodium hydroxide solutions were used. Peak stress, ultimate strain and slope of stress–strain curve of stabilized clay are controlled by Na/Al and Si/Al ratios. Stress–strain response and peak stress of slag and fly ash blended specimen are not governed by Na/Al and Si/Al ratios; rather the behavior is dependent predominantly on slag content. 相似文献
18.
冻融条件TG固化剂石灰土基层性能研究 总被引：2，自引：2，他引：0
为了进一步研究TG固化剂石灰土在冻融条件下的各项性能, 分别对TG固化剂石灰土进行冻融作用前后的无侧限抗压强度试验和劈裂试验以及干缩试验. 结果表明: 随着冻融循环次数的增加, 无侧限抗压强度以及劈裂强度逐渐减小, 经历8次冻融循环以后强度衰减达到最大值. 经过冻融循环作用后试件的无侧限抗压强度以及劈裂强度残留值随着含水率和压实度的增加而增加, 通过冻融试验得到的抗冻性能指标BDR值在51%以上, 与未饱水冻融循环得到的最终残留强度值保持一致. 经冻融循环作用后TG固化剂石灰土的干缩应变和干缩系数减小, 干缩性能有所提高. 冻融循环条件下TG固化剂石灰土抗冻性能良好, 可以应用于路面基层. 相似文献
19.
Riverine organic carbon in the Xijiang River (South China): seasonal variation in content and flux budget 总被引：11，自引：0，他引：11
20.
研究掺粉煤灰对合肥膨胀土的物理性质指标以及胀缩性指标等的影响,探讨利用粉煤灰改良膨胀土的措施与效果。试验研究结果表明,在膨胀土中掺入适量的粉煤灰可有效降低膨胀土的塑性指数、降低膨胀势、减小线缩率与降低活性。在膨胀土中掺入粉煤灰还可改变膨胀土的击实特性,一定击实功作用下,随着掺灰率的增加,土体的最优含水率与最大干密度均减小,膨胀土中掺入粉煤灰后,膨胀土可在较小的含水率下通过击实或压实达到稳定。掺灰膨胀土的膨胀量与膨胀力随养护龄期的增长而减小;没有经过养护的掺灰土,其无侧限抗压强度随掺灰率的变化几乎没有变化,经过7 d养护后,土的无侧限抗压强度有所增长,并且存在一个峰值点,合肥膨胀土的无侧限抗压强度所对应的最佳掺粉煤灰率约为15 %～20 %。 相似文献