碱激发钢渣粉淤泥固化土性能研究

在淤泥土等不良土质中水泥固化存在抗压强度低、水泥消耗量大等问题,分析了钢渣粉掺量、养护龄期、激发剂等对固化土抗压强度的影响规律。结果表明:当钢渣粉掺量超过10%,固化土7 d抗压强度快速降低,28 d抗压强度逐渐提高;NaOH和Na2CO3对钢渣基淤泥固化土影响类似,低掺量效果有限,20%掺量固化土28 d抗压强度分别提高至1.33 MPa和1.67 MPa。复合碱激发材料对固化土的抗压强度提高效果优于单一碱激发材料,10%NaOH复合10%Na2CO3固化土28 d抗压强度达到2.37 MPa。SEM表明,复合碱激发材料的掺入可促使淤泥固化土内部产生更多的硅酸钙凝胶,减少孔隙,提升整体密实性,从而提高了固化土抗压强度。     

电石渣固化软土的强度特性研究

本文采用电石渣、矿渣、粉煤灰为主要固化剂组分,测试电石渣单独固化土以及电石渣与矿渣、粉煤灰共同固化土的强度特性,检测电石渣固化土的效果。结果表明:采用电石渣单独固化土,固化土强度随电石渣掺量增加呈现先增大后减小的趋势,电石渣掺量为20%时,固化土强度最高。适量增加土样的含水率有利于增加电石渣固化土的强度。当电石渣掺量为15%时,土样含水率增加5%,固化土强度最佳;当电石渣掺量为20%和25%时,土样含水率增加3%,固化土强度最佳。电石渣激发矿渣和粉煤灰共同固化土效果显著,电石渣与矿渣、粉煤灰之间都存在一个最佳配合比,矿渣:电石渣=9:1,粉煤灰:电石渣=8:2是最佳配合比。     

工业废渣–水泥协同固化土抗硫酸盐侵蚀性能

利用高炉矿渣、粉煤灰、硅灰、电石渣等工业废渣协同水泥固化方法,通过标准养护试样、清水及硫酸盐溶液浸泡试样的表观形貌、无侧限抗压强度、X射线衍射和扫描电镜等测试,揭示工业废渣–水泥协同固化土的力学性能、微观结构和化学反应机制。结果表明：硫酸镁对工业废渣–水泥协同固化土侵蚀效果大于硫酸钠;较纯水泥土而言,工业废渣的加入能够延缓硫酸盐侵蚀作用;经硫酸镁溶液浸泡后,固化土强度在7 d内有一定增长,之后随龄期增加而持续降低,强度保留系数高低依次为高炉矿渣>硅灰>粉煤灰>电石渣;硫酸钠环境下固化土受SO₄^2-离子侵蚀作用,硫酸镁环境下受SO₄^2-侵蚀和Mg²⁺胶结弱化双重作用,导致固化土孔隙增大,侵蚀产物生成量与工业废渣中CaO含量有关。最后,建立了硫酸盐环境下固化土微观反应机制模型,可为工业废渣–水泥协同固化土抗硫酸盐侵蚀研究提供理论依据。     

等强度条件下碱激发高炉镍渣混凝土与普通硅酸盐水泥混凝土的性能对比

分别以NaOH和水玻璃为激发剂，制备了碱激发高炉镍渣混凝土，在碱激发高炉镍渣混凝土的7 d抗压强度与普通硅酸盐水泥混凝土的28 d抗压强度基本相等的条件下，对比了碱激发高炉镍渣混凝土和普通硅酸盐水泥混凝土的后期（90 d）力学性能、孔结构发展规律和抗氯离子渗透性能的差异。结果表明：碱激发高炉镍渣混凝土的早期（7 d前）强度发展迅速，其中，NaOH激发高炉镍渣混凝土28 d后的强度发展相对缓慢；等强度条件下，碱激发高炉镍渣混凝土的后期抗压强度和劈裂抗拉强度、孔结构和抗氯离子渗透性能均优于普通硅酸盐水泥混凝土，其中，水玻璃激发高炉镍渣混凝土的各项性能最好。     

碱激发赤泥-粉煤灰-电石渣复合材料性能研究

采用(NaOH+Na₂SiO₃)溶液、电石渣和粉煤灰来稳定赤泥,制备了碱激发赤泥-粉煤灰-电石渣复合材料.通过力学和微观性能测试,分析了复合材料的强度形成和发展机理,并通过重金属浸出试验评价了复合材料的安全性.结果表明：复合材料的强度随着赤泥掺量的降低和养护龄期的延长而提高,掺40%赤泥的复合材料在28 d龄期时的抗压强度最高可达20.1 MPa,致密的水化硅酸钙(C-S-H)和水化铝酸钙(C-A-H)的形成及赤泥颗粒的物理结合是复合材料强度增长的主要原因;赤泥中的重金属在养护28 d后形成了化合物而被固化在复合材料中,在浸泡28 d后的浸出液中未检测到重金属,证明使用强碱激发剂、电石渣和粉煤灰稳定赤泥是安全可行的.     

电石渣-火山灰质胶凝材料固化盐渍土试验研究

以电石渣、粉煤灰和碱激发剂作为原材料制备一种盐渍土固化剂,采用正交试验方法研究各因素对固化盐渍土击实性能和抗压强度的影响,并探索电石渣-火山灰质胶凝体系固化盐渍土的固化机理和水化产物。结果表明:各因素对固化盐渍土抗压强度的影响顺序为:碱激发剂>胶凝材料掺量>m(电石渣)∶m(粉煤灰);固化盐渍土养护7 d抗压强度和水稳定性满足实际工程中对固化盐渍土强度的需求;在电石渣和碱激发剂双重激发下粉煤灰发生火山灰反应,反应产物以水化硅酸钙凝胶、钙矾石和二水石膏为主。当养护龄期为360 d时,试件内未发现明显的Ca(OH)2存留,说明固化土试件养护360 d时,火山灰反应基本完成。     

NaCl侵蚀环境下水泥固化铅污染土强度及微观特性试验研究

含有硫酸盐及盐酸盐等高含盐量的地下水环境,对固化/稳定法处置的重金属污染土的工程性质可能存在一定的影响,进而直接影响土体的固化效果。通过系统的室内试验,着重研究水泥固化铅污染土在Na Cl溶液侵蚀环境下的强度特性和微观结构特征。试验结果表明,固化土的无侧限抗压强度随着Na Cl溶液浓度的增加而减小,压缩性随Na Cl浓度的增加而增大。浸泡7 d时,其强度最小,压缩性最大;超过7 d后,强度随浸泡时间的增加而增大,压缩性则随之减小。三轴试验结果表明,固化土的应力–应变特性大致分为弹性变形、塑性屈服和破坏阶段3个不同阶段。由于Na Cl的侵蚀作用,浸泡7 d的固化土中孔隙增多,结构较为疏松,浸泡28和90 d试样的颗粒排列较7 d要致密规则。     

高含水量软土水泥土强度特性影响因素研究

针对福州市沿海滨海高含水量软土低强度和高压缩性的问题,在室内采用水泥进行固化配方试验。对两种典型软土,即淤泥和淤泥质粘性土进行固化处理,分析了固化时间、水泥掺量、固化方式和软土本身含水量对强度的影响。通过试验研究发现:(1)在固化龄期的前28d内,水泥土强度增长明显,速率较大。在28d~90d内强度逐渐增大,但增速降低,后逐渐趋缓,水泥土强度与龄期之间近似呈对数关系。(2)水泥掺量越高,水泥土强度也越大,但在实际复合地基工程中,水泥掺量不宜过大。(3)粉喷制作的水泥土强度比浆喷制作的强度高出12%~36%,且随着固化龄期的增长,提高的比例有所增大。(4)当水泥掺量较低时,软土本身含水量越高,制作的水泥土强度越低。     

水泥固化东莞滨海湾软土的强度特性及劣化机理试验研究

基于粤港澳大湾区的发展,东莞滨海湾软土由于其具有高有机质、高含水率、高压缩性和变形稳定时间过长等较差的工程性质,极大限制了区域的建设能力,因此需要使用水泥来固化软土从而提高其工程物理力学性质。以不同养护龄期和不同水泥掺量为变量探究固化软土的强度特性,养护28 d后的试样分别浸泡7d、14 d、28 d后的无侧限抗压强度研究其劣化特性,试验结果表明：随着养护时间和水泥掺量的增加,东莞滨海湾水泥固化土的强度也会随之提高,最高提升83.6%;试样强度在浸泡7 d后先下降,随后在14 d和28 d出现上升的趋势,且浸泡28 d的强度大于养护28 d的强度。     

不同火山灰质材料的火山灰反应效益研究

主要研究火山渣的火山灰反应效益,并与粉煤灰及矿渣进行了对比。结果表明,3 d时火山渣对水泥砂浆体系的强度没有贡献,28 d、90 d、180 d时对强度有贡献,但贡献小于硅酸盐水泥;3 d、28 d、90 d、180 d时粉煤灰对水泥砂浆体系的强度有贡献,但贡献小于硅酸盐水泥;3 d时矿渣粉对水泥砂浆体系强度的贡献小于硅酸盐水泥,28 d、90 d、180 d时对强度的贡献大于硅酸盐水泥。随着火山渣细度增加及水化龄期的延长,火山渣的火山灰反应效益呈增大趋势。     

Study on the optimization and performance of GFC soil stabilizer based on response surface methodology in soft soil stabilization

In order to improve the utilization efficiency of industrial waste residue and the treatment effect of marine soft soil, ground granulated blast furnace slag (GGBS), flue gas desulfurization gypsum (FGDG) and calcium carbide slag (CCS) were used to modify the waste soft soil in coastal areas. Using the box-behnken design (BBD) in response surface analysis, the optimal mix ratio design of GGBS, FGDG and CCS was obtained. Meanwhile, under the same conditions, the mechanical properties, durability and micro mechanism of industrial waste residue stabilized soil was studied and compared with that of OPC stabilized soil by the unconfined compressive strength (UCS) test, water stability test, freeze–thaw cycle test, X-ray diffraction and scanning electron microscope (SEM) test. Experimental results showed that the optimal mixing ratio of GGBS, FGDG and CCS was 61: 8: 31; the UCS of GFC stabilized soil exceeded 8.7 MPa at 28d. The UCS of GFC stabilized soil at 28d was 1.23 times higher than that of OPC stabilized soil. GFC stabilized soil also possessed superior durability than OPC stabilized soil. Micro mechanism analysis showed that gel hydration products (CSH, CAOH) and expansive hydration product (AFt) were produced in GFC stabilized soil. These hydration products led to the aggregation and condensation of soil particles, which made the soil structure denser through bonding and filling effects, thus increased strength of stabilized soil.     

黄河三角洲改性含盐水泥土搅拌桩耐久性研究

通过室内试验,研究了黄河三角洲含盐水泥土的劣化规律以及粉煤灰和矿渣微粉对其劣化的抑制效应,并利用X射线衍射（XRD）和扫描电镜（SEM）对劣化机理及外加剂的改性机理进行了分析.结果表明：地下盐水环境对黄河三角洲水泥土有较强的腐蚀作用,其90,180d龄期的抗压强度分别降低了18.5%,21.6%;掺加粉煤灰对黄河三角洲含盐水泥土的早期强度不利,但其后期强度会持续增加;掺加矿渣微粉对黄河三角洲含盐水泥土强度有明显的提升作用,并对其劣化有显著的抑制作用.为防止黄河三角洲含盐水泥土劣化,工程中建议用粉煤灰和矿渣微粉等质量替代60%的水泥,而且矿渣微粉掺量不少于40%.     

Stiffness and strength development of the soft clay stabilized by the one-part geopolymer under one-dimensional compressive loading

In this paper, the one-part alkali-activated geopolymer was adopted as the soil binder to stabilize the soft clay under the one-dimensional compressive loading. Factors influencing the stiffness and strength of the one-part geopolymer stabilized soil such as the proportion of silicon-aluminum raw materials, the mass ratio of solid NaOH (NH) to raw materials and the water-binder ratio were taken into account. The stiffness development of the one-part geopolymer stabilized soft clay under one-dimensional compressive loading was investigated by an improved transducer system equipped with a pair of bender extender elements and the tactile pressure sensor, from which the time history of earth pressure coefficient (i.e., K₀) and elastic wave velocity (i.e., the compression wave velocity V_P and the shear wave velocity V_S) of the stabilized soil sample could be measured, respectively. Furthermore, the unconfined compressive strength (UCS) of the stabilized soil sample cured under varied one-dimensional compressive loadings was tested to reveal the strength development of the geopolymer stabilized soil sample. Among different mixing proportions, the alkali-activated binary precursor [90% ground granulated blast furnace slag (GGBFS) and 10% fly ash (FA)] exhibits the highest performance in terms of the V_S, V_P and UCS of the geopolymer stabilized soil sample when the activator/precursor and water/solid ratio are 0.15 and 0.7 (i.e., the 4.67 mol/L of NH solution), respectively. The prediction of UCS for the one-part geopolymer stabilized soft clay was proposed and established based on the elastic wave velocity (i.e., V_S and V_P). The outcome of the current study sheds light on the practical use of the one-part alkali-activated geopolymer as a soil binder in ground improvement.     

碱激发钒尾矿-矿渣基地聚合物的研究

以钒尾矿为硅铝质原料、以矿渣为促硬剂、以硅灰和氢氧化钠复合作为碱激发剂制备地聚合物。研究活化钒尾矿和矿渣的比例、激发剂中SiO2和Na2O的比例以及养护温度对地聚合物早期性能的影响。结果表明,在合适的碱性条件下,加入适量的矿渣后,由矿渣中活性Ca形成的水化硅酸钙(CSH)可在地聚合物结构中起到微集料填充的作用,从而提高地聚合物的早期强度。当活化钒尾矿和矿渣的质量比为60∶40,激发剂中SiO2和Na2O的摩尔比为2.0时,在65℃下养护24 h,再在室温条件下放置3 d后地聚合物样品的抗压强度可达到35.1 MPa。随着矿渣所占比例的增大,凝结时间先缩短后延长;随着激发剂中SiO2和Na2O比例的减小,凝结时间先缩短后延长。     

Effect of polypropylene fiber and nano-zeolite on stabilized soft soil under wet-dry cycles

Nano-zeolite was used in the present study as a substitute for a part of lime and then inclusion polypropylene fiber in stabilized soil matrix to develop the soil stabilization method with lime and to improve the efficiency of this technique. In so doing, specimens of soft soil with 5, 10 and 15% of modifier L (lime), LZ (lime-nano-zeolite) and LZF (lime-nano-zeolite-fiber) were prepared, and were subjected to 1–7 wet-dry cycles. Then, microstructure and macrostructure tests were performed on the specimens. The results of the analyses, indicated that the optimal replacement of lime with nano-zeolite would be 40%, and the optimal amount of polypropylene fibers inclusion would be 1% in the stabilized soil matrix. Major reduction in lime consumption would yield a 40% increase in compressive strength and a 21% improvement in durability. The results also showed that the specimen containing 15%LZF would have excellent durability against environmental conditions and very good performance in terms of unconfined compressive strength (UCS), tensile strength and weight loss. Before and after applying 7 wet-dry cycles, the UCS increased by 39% and 16%, respectively. The results of this study indicate that LZF modifier is a suitable option for lime-based stabilization in areas under wet-dry cycles.     

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects. However, due to the high carbon emission in cement production, research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years. This research investigated the potential of using alkali-activated ground granulated blast furnace slag (GGBS) and volcanic ash (VA) as green binders in clayey soil stabilization projects, which has not been studied before. The effects of different combinations of VA with GGBS, various liquid/solid ratios, different curing conditions, and different curing periods (i.e. 7 d, 28 d and 90 d) were investigated. Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests. The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels. Moreover, although VA needs heat curing to become activated and develop strength, its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles. The carbon embodied of the mixtures was also evaluated, and the results confirmed the low carbon footprints of the alkali-activated mixtures. Finally, it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.     

Utilization of carbide slag-activated ground granulated blastfurnace slag to treat gypseous soil

Treating gypseous soils with lime or cement may induce remarkable swelling, resulting in the deterioration of pavement subgrade or other foundation layers. To mitigate this swelling, two industry by-products, carbide slag (CS) and ground granulated blastfurnace slag (GGBS), were utilized in this study. The CS was used to activate the GGBS, which was used to treat an artificial gypseous soil with different binder contents and CS:GGBS ratios, compared to ordinary Portland cement. The treated soils were soaked after a 7-day curing period. A series of tests was performed to examine the properties of the treated soils, including swelling, strength, water content, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). It was found that the CS-GGBS-treated soils experienced slightly higher swelling (0.2%–1.0%) than the cement-treated soils (0.1%–0.3%) during the 7-day curing period. However, the following soaking process significantly increased the swelling of the cement-treated soils (>5.0%), caused cracks on the specimen surface, and reduced the strength, whilst the swelling of the CS-GGBS-treated soils after soaking was much lower (<0.3%), no cracks were observed, and the decrease in the soaking-induced strength was much less. The XRD, SEM, and MIP results indicated that the formation of ettringite was primarily responsible for the swelling. For the CS-GGBS-treated soils, the activation of GGBS and the formation of ettringite at an early age (within 7 days) rapidly consumed the Ca(OH)₂ in the CS; and hence, the further formation of ettringite after soaking was very limited. For the cement-treated soils, the cement hydration continuously supplied Ca(OH)₂ for the ettringite formation until completion, resulting in longer and higher swelling after soaking.     

粉煤灰炉渣加固土的室内无侧限抗压强度试验研究(英文)

给出了用粉煤灰、炉渣等工业废料加固土的室内无侧限抗压强度试验结果,分析了加固土无侧限抗压强度与外加剂掺量、养护龄期之间的影响规律,得出了针对不同工业废料加固土所用外加剂的最佳掺量。     

含铝固化剂固化软土的试验研究

用普通硅酸盐水泥、石膏和一种含铝膨胀组分构成的复合固化剂（PC＋G＋Al固化剂）,选取2种有代表性的试样,进行软土固化试验研究,并与单纯使用水泥（PC）和水泥-石膏（PC＋G）固化剂加固软土的效果进行比较分析。研究结果表明：对2种试样,PC＋G＋Al固化剂加固效果优于其他2种固化剂;PC＋G固化剂只对孔隙比大、含水率高的试样加固效果优于PC固化剂的加固效果。PC＋G＋Al和PC＋G固化剂的水化物中都产生钙矾石,利用钙矾石生成的固相膨胀作用填充孔隙,而钙矾石的生成在固化土中是否产生增强效果,主要取决于钙矾石与水化硅酸钙凝胶生成过程的协调性。     

Mechanical and leaching behaviour of slag-cement and lime-activated slag stabilised/solidified contaminated soil

Stabilisation/solidification (S/S) is an effective technique for reducing the leachability of contaminants in soils. Very few studies have investigated the use of ground granulated blast furnace slag (GGBS) for S/S treatment of contaminated soils, although it has been shown to be effective in ground improvement. This study sought to investigate the potential of GGBS activated by cement and lime for S/S treatment of a mixed contaminated soil. A sandy soil spiked with 3000 mg/kg each of a cocktail of heavy metals (Cd, Ni, Zn, Cu and Pb) and 10,000 mg/kg of diesel was treated with binder blends of one part hydrated lime to four parts GGBS (lime-slag), and one part cement to nine parts GGBS (slag-cement). Three binder dosages, 5, 10 and 20% (m/m) were used and contaminated soil-cement samples were compacted to their optimum water contents. The effectiveness of the treatment was assessed using unconfined compressive strength (UCS), permeability and acid neutralisation capacity (ANC) tests with determination of contaminant leachability at the different acid additions. UCS values of up to 800 kPa were recorded at 28 days. The lowest coefficient of permeability recorded was 5 × 10^− 9 m/s. With up to 20% binder dosage, the leachability of the contaminants was reduced to meet relevant environmental quality standards and landfill waste acceptance criteria. The pH-dependent leachability of the metals decreased over time. The results show that GGBS activated by cement and lime would be effective in reducing the leachability of contaminants in contaminated soils.