Influencing factors of compressive strength of solidified inshore saline soil using SH lime-ash

Through unconfined compressive strength test,influencing factors on compressive strength of solidified inshore saline soil with SH lime-ash,ratio of lime-ash(1-K),quantity of lime-ash,age,degree of compression and salt content were studied.The results show that because inshore saline soil has special engineering characteristic,more influencing factors must be considered compared with ordinary soil for the perfect effect of solidifying.

Mechanism and Optimal Application of Chemical Additives for Accelerating Early Strength of Lime-flyash Stabilized Soils

To accelerate the early strength of lime-flyush stabilized soil for extending its further uses in highway and shortening highway constraction time, five kinds of chemical odditives were chosen on the basis of mechanism analysis of accelerating early strength in highway as a semi-rigid base materhd, and a series of experiments about the effect of differeat kinds of additives and quantity on the early strength of the stabilized soll were tested. The results show that chemical additives can efftciently improve the early strength of lime-flyush stabilized soil both the 7 d and 28d, and the optimum quantity for above chemical additive is 1.5%-2.5% approximately. Some suggestions for the practical construction were also proposed.

Importance of Sand Grading on the Compressive Strength and Stiffness of Lime Mortar in Small Scale Model Studies

Mortars provide the continuity required for the stability and exclusion of weather elements in masonry assemblies. But because of the heterogeneity of the mortar, its mechanism of behaviour under different load effects is dependent on the properties of the constituents of the mortar. The aim of paper is to determine the effect sand grading for various cement-sand-lime mortar designations (BS) and strength classes (EC) on the compressive strength and stiffness of mortar. Two silica sands;HST 95 and HST60 were used to make mortars in three strength classes: M2, M4 and M6, corresponding to mortar designations iv, iii and ii respectively. The results show that mortar made with the HST60 sand (coarser grading) usually resulted in mortar with a higher compressive strength and stiffness. The One Way ANOVA analysis of both compressive strength and stiffness at a significance level of 5% on the effect of sand grading on the two parameters also shows that they are both significant. There is also strong evidence of a linear correlation between the stiffness and compressive strength. The results indicate that in order to replicate full scale behaviour of masonry at model scales, the grading of fine aggregate in the models should be similar so as to properly model full scale behavior.

Influence of Salt-Lime Stabilization on Soil Strength for Construction on Soft Clay

Construction on soft soil is one of the most challenging situations faced by geotechnical engineers. The heterogeneous and complex nature of soil, especially those containing organic clay, often makes it impossible for the construction specification to be addressed properly. Generally, clay exhibits low strength, high compressibility, and strength reduction when subjected to mechanical disturbance. This means that construction on clay soil is vulnerable to bearing capacity failure induced by low inherent shear strength. All these properties can be improved by the effective stabilization of soil. This study analyzed the effectiveness of incorporating salt-lime mixtures at various dosages in improving the strength increment of the soil. The results indicate that among different combinations of salt and lime, the best performance in terms of strength increase was achieved by adding 10% NaCl with 3% lime in the soil. The outcome of this study focuses on enhancing the ultimate strength of soil and its implementation in the field of foundation engineering.

Influence Factor Analysis on Strength of Lime-Fly Ash Loess

Lime-fly ash loess is composed of fly ash, lime and loess. It is a new material in subgrade backfill. Main factors to influence the strength of lime-fly ash loess are age, amount of fly ash and lime, ratio of fly ash to lime (1:K), and moisture content. In order to observe the effect of each factor influencing the strength of lime-fly ash loess and find out the relationship between each other, this paper adopted orthogonal test design to conduct unconfined compression tests. The result shows that 90d strength can be considered to calculate the strength of lime-fly ash loess in practice. And the most important factor to influence the 90d strength of lime-fly ash loess is the amount of fly ash and lime, the second is moisture content, and then is the ratio of fly ash to lime (1:K). These achievements are significant to the design and application of lime-fly ash loess in subgrade construction of loess areas.

Assessment of Cement-Lime as Stabilizer on Mud Bricks

The aim of this study was to evaluate the compressive strength of clay bricks and their stability to water absorption by inserting stabilizers such as lime and cement of 0%, 4%, 6%, 8%, 10%, 12% to 14%. Spectrometric analysis was used to characterize the various stabilizers and the clay used, and tests of resistance and water absorption were also carried out. The clay was found to be an aluminosilicate (15.55% to 17.17% Al2O3 and 42.12% to 44.15% SiO2). The lime contains 90.84% CaO and the cement has 17.80% SiO2, 3.46% Al2O3, 2.43% Fe2O3 and 58.47% CaO in the combined form of tricalcium silicate, dicalcium silicate, tricalcium aluminate and ferro-tetra calcium aluminate. The results showed that the insertion of locally available stabilizers (lime and cement) improved the strength of the material by almost 80% when the lime was increased from 0% to 14% for 14 days. For compressed cement, a 65% increase in strength was observed under the same conditions. Strength increases with drying time, with a 52% increase in strength at 28 days compared to 14 days. Furthermore, compressed cement bricks have a more compact structure, absorbing very little water (32%). In view of all these results, cement appears to be the best stabilizer, and compression improves compressive strength and reduces water absorption.

Effects of lime addition on geotechnical properties of sedimentary soil in Curitiba,Brazil

The soil of the Guabirotuba geological formation（Paraná Basin, Brazil） has physico-mechanical properties which are not suitable for its utilization in pavement construction, in protection of hillsides and slopes, or as shallow foundation support. Treatment of this soil by lime addition would improve its usability. The present context intends to determine the ratio between the splitting tensile strength（q;）and the unconfined compressive strength（q;） of clayey soil in the metropolitan region of Curitiba City,which has been treated with different lime contents and curing times. The control parameters evaluated include lime content（L）, curing time（t）, moisture content（w）, and ratio of porosity to volumetric lime content（η/L;）. It was observed that the q;/q;ratio is between 0.17 and 0.2 in relation to the curing time,and an exponential relation exists between them. Meanwhile, the unconfined compressive strength of lime-treated soil was found to be approximately four times the initial value.

Experimental Investigation of Lime Treated Palm Kernel Shell and Sugarcane Bagasse Ash as Partial Replacement of Coarse Aggregate and Cement Respectively in Concrete

This experimental research is focused on the effect of concrete made by incorporating lime treated Palm Kernel Shell (PKS) & Sugarcane Bagasse Ash (SCBA) as partial replacements of coarse aggregates and Ordinary Portland Cement (OPC) respectively. An experimental analysis for concrete grade 30 with a mix design ratio of 1:1.97:3.71 of cement:fine aggregates:coarse aggregates with a constant water to cement ratio of 0.5, was used. Physical tests such as workability on fresh concrete and water absorption on hardened concrete of each batch were carried out. Mechanical tests like compressive strength and split tensile strength were carried out on hardened concrete cubes (100 mm × 100 mm × 100 mm) and cylinders (100 mm × 200 mm) at 7 and 28 days. The experimental results obtained in this study indicate the possibility of using up 15% of lime treated PKS and 10% of SCBA for production of structural concrete.

Effect of Curing Environment on the Strength Properties of Cement and Cement Extenders

Curing of cement based products such as concrete and mortar, is very important to achieve good strength and durable products. However the curing environment plays a pivotal role in the overall quality of cement based products in terms of strength development. ASTM C192 allows moist curing either in a fog room or under water. However, these must meet ASTM C511 which controls temperature, and specifically for water curing, the concentration of calcium ions in the curing solution. Unfortunately in many parts of the world, water curing literally means curing in tap water. This is done primarily because there is a lack of knowledge or ignorance regarding the mobility and roll of calcium hydroxide in the curing process. To illustrate the differences, in this study, straight ASTM Type I/II Portland cement and that mixed with powdered waste clay bricks as a cement extender were used to prepare two different batches of mortars. The chemical properties of the powdered waste clay brick met the ASTM C618 standard specifications for Class N pozzolans. Both mortar specimens were cured under two different environment comprising of either water and lime saturated water. Mortar specimens were tested for compressive strength at 3, 7, 14 and 28 days of either curing conditions. Test results indicated that mortar specimens cured in lime saturated water obtained higher strength than those cured in fresh water at all ages of curing. Statistical inference drawn from ANOVA testing showed that curing conditions had significant impact on strength development of the blended and unblended cement systems. The study recommends that testing of concrete and mortar samples and other research related works be performed in lime saturated water other than fresh water.

石灰-沸石粉改良膨胀土强度特性及微观机理研究

针对膨胀土胀缩性造成的工程病害问题及石灰改良膨胀土产生的污染问题,以河南南阳地区膨胀土为研究对象,制备素膨胀土及不同石灰和沸石粉掺量的改良土试样。对试样进行无侧限抗压试验、自由膨胀率试验、三轴试验、X射线衍射(XRD)分析和扫描电子显微镜(SEM)测试,研究石灰-沸石粉复合改良膨胀土的强度特性及微观加固机理。结果表明:石灰改良和石灰-沸石粉复合改良均能有效增强土体的强度并降低自由膨胀率,复合改良效果更好,石灰和沸石粉的最佳掺量分别为6%(质量分数)和12%(质量分数);石灰改良土和复合改良土的应力-应变曲线转化为应变软化型;石灰的加入显著提升了膨胀土的黏聚力,随着沸石粉掺量的递增,复合改良土三轴抗剪强度不断增大,内摩擦角呈先增大后减小的趋势;沸石粉与石灰发生火山灰反应,生成大量胶凝物质,填充土体孔隙并使微观结构更加密实,增强土颗粒间的摩阻力,宏观层面上土体强度增强。

石灰-高炉矿渣改良膨胀土强度特性试验研究

因膨胀土具有吸水膨胀、失水收缩等不稳定性特征,使用高炉矿渣作为新型固化剂,并与无机材料石灰组合对膨胀土进行改良。对改良膨胀土开展自由膨胀率、液塑限、无侧限抗压强度和抗剪强度等指标的研究,探讨并分析了石灰-高炉矿渣(L-BLS)改良膨胀土在不同养护龄期以及不同改良剂掺量下的无侧限抗压强度变化规律。结果表明:使用L-BLS改良膨胀土能够显著提高膨胀土的早期强度;改良膨胀土的强度随养护龄期及改良剂掺量的增加而增强;当掺入6%石灰及9%高炉矿渣时,对应龄期的无侧限抗压强度最大,材料的有效利用率最佳。

掺氢氧化钙对超高强混凝土力学性能影响的机理

鉴于含矿物掺合料较多的超高性能混凝土(Ultra-high performance concrete,UHPC)中火山灰反应所需氢氧化钙含量不足的状况,在配制超高强混凝土(UHPC基体)时掺加氢氧化钙,研究其对超高强混凝土力学性能的影响机理。结果表明,超高强混凝土力学性能的改善源于掺入的氢氧化钙与矿物掺合料中的SiO_(2)发生火山灰反应生成C-S-H及C-A-S-H凝胶,且在组合养护(90℃热水养护2 d+250℃干热养护3 d)下,部分C-(A)-S-H凝胶向托勃莫来石与硬硅钙石晶体转变,改善了超高强混凝土的微观结构。

Effect of curing, capillary action, and groundwater level increment on geotechnical properties of lime concrete: Experimental and prediction studies

Lime concrete and lime treatment are two attractive techniques for geotechnical engineers.However,researches have rarely been carried out to study the effects of moisture and capillary action due to increasing groundwater level on geotechnical properties of lime concrete.The aim of this study is to investigate the effects of curing time and degree of saturation on some of geotechnical properties of lime concrete such as unconfined compressive strength(UCS),secant modulus(ES),failure strain,brittleness index(IB),and deformability index(ID) using unconfined compression tests.First of all,geotechnical and chemical properties of used materials were determined.After curing times of 14 d,28 d,45 d,and 60 d in laboratory condition,the specimens were exposed to saturation levels ranging from 0 to 100%.The results showed that the moisture and curing time have significant effects on the properties of lime concrete.Based on the results of scanning electron micrograph(SEM) test,it was observed that the specimen was characterized by a rather well-structured matrix since both the filling of a large proportion of the coarse-grained soil voids by clay and the pozzolanic activity of lime led to retaining less pore water in the specimen,increasing the UCS and ES,and consequently resisting against swelling and shrinkage of the clay soil.Moreover,due to the pozzolanic reactions and reduction of water,by increasing the curing time and decreasing the degrees of saturation,UCS,ES,and IBincreased,and IDdecreased.Based on the experimental results,a phenomenological model was used to develop equations for predicting the properties in relation to the ratio of degree of saturation/curing time.The results showed that there was a good correlation(almost R2> 90%) between the measured parameters and the estimated ones given by the predicted equations.

Discussion on "Effects of lime addition on geotechnical properties of sedimentary soil in Curitiba, Brazil" [J Rock Mech Geotech Eng 10(2018)188-194]

The present discussion aims at complementing the original work published by Baldovino et al.(2018) by outlining a novel point of view. In light of the inherent limitations associated with the empirical model suggested in the original article, the dimensional analysis technique was introduced to the soil-lime strength problem, thereby leading to the development of simple and physically meaningful dimensional models capable of predicting the unconfined compressive and splitting tensile strengths of compacted soil-lime mixtures as a function of the mixture's index properties, i.e. lime content, initial placement(or compaction) condition, initial specific surface area and curing time. The predictive capacity of the proposed dimensional models was examined and validated by statistical techniques. The proposed dimensional models contain a limited number of fitting parameters, which can be calibrated by minimal experimental effort and hence implemented for predictive purposes.

冻结二灰固化碳酸盐渍土及损伤模型研究

在寒区工程中,盐-冻耦合效应往往会放大盐渍土体的强度损失。因此,考虑探究冻结作用下二灰固化碳酸盐渍土抗压性能的变化规律,以固化剂掺量、温度和加载速率作为影响因素,对二灰固化盐渍土进行了无侧限抗压试验,并提出一种考虑温度和加载速率的二灰固化盐渍土损伤本构模型。结果表明:石灰和粉煤灰能明显提高碳酸盐渍土的抗压强度,且使得改良土的应力-应变曲线由应变弱软化变为应变明显软化,当掺入3%石灰和12%粉煤灰时对碳酸盐渍土的固化效果最显著;温度和加载速率显著影响二灰固化土的抗压强度和弹性模量,三者之间关系可用非线性函数表达;二灰固化土抗压强度的影响因素按照重要性排序为温度>固化剂掺量>加载速率,且温度对改良土的影响远大于固化剂掺量和加载速率;所构建的二灰固化土损伤模型能较好地反映土体的应力应变关系和损伤变量的变化趋势。

浸水环境下石灰-聚丙烯纤维改良盐渍土的强度特性与水稳定性研究

为了探究浸水环境下石灰-聚丙烯纤维改良盐渍土的强度特性与水稳定性,通过室内试验对不同浸水天数下改良土的抗压强度与体积膨胀率进行研究并采用响应曲面法对土体改良工艺进行优化。结果表明,在浸水环境下,石灰与纤维可以有效提升改良土的抗压强度与水稳定性,最优石灰掺量与最优纤维掺量分别为8%、0.4%。通过控制土体中的含盐量以及盐分中Na_(2)SO_(4)所占比例也可使改良土的抗压强度与水稳定性得到有效提升,最优含盐量以及Na_(2)SO_(4)的最优占比分别为1%、25%。随着浸水天数的增加,改良土的抗压强度呈现出先大幅度降低后缓慢增加的趋势,而体积膨胀率则呈现出逐渐增大后趋于平缓的趋势。经过响应曲面优化后得出改良土的最大抗压强度为602.542 k Pa,与其相对应的最佳试验变量组合为:石灰掺量7.41%、纤维掺量0.38%、含盐量1.27%、盐分中Na_(2)SO_(4)所占比例24.91%;最小体积膨胀率为0.288%,与其相对应的最佳试验变量组合为:石灰掺量6.53%、纤维掺量0.38%、含盐量1.21%、盐分中Na_(2)SO_(4)所占比例29.92%。研究成果可为盐渍土地区的工程建设提供理论依据与参数支持,并且达到对盐渍土资源化利用的目的。

氟石膏和熟石灰碳化养护力学性能的研究

氟石膏是干法氟化铝或湿法氢氟酸生产的过程中排放的废渣,其主要成分是CaSO_(4)。为综合利用氟石膏,研究利用熟石灰和快速碳化养护去增强氟石膏的抗压强度和软化系数。采用DTA-TG、XRD和SEM-EDS对比分析了在不同氟石膏和熟石灰比例、不同水料比时,复合材料体系硬化后的性状。研究结果表明,当水料比为0.1,随着熟石灰掺量的增加,复合材料抗压强度由原来(未掺加熟石灰)的2.4 MPa增大到22.4 MPa。XRD、DTA-TG和SEM-EDS的测试结果表明,复合材料反应产物为二水石膏和碳酸钙,当熟石灰掺量为50%和70%时,碳酸钙的含量相对较高。熟石灰激发及快速碳化养护的协同作用下,氟石膏的力学强度及耐水性均得到提高,这为石膏基建筑材料的生产和研究具有较好的指导意义。

石灰粉粒度分布对压球效果影响研究

为提高石灰成球装置的石灰球团的强度和成球率,使石灰压球装置高效使用,利用现有试验室压球机开展了不同粒径石灰粉料的压球成型试验。结果发现,采用小于5 mm石灰颗粒的石灰球团强度和成球率较高,并对现场装置提出了诸多建议。

石灰改良土浸水稳定性及其影响因素研究

为了研究石灰改良黄土在长期浸水条件下的强度劣化特性,采用振动法成型石灰改良黄土试件,研究了浸水时间、压实系数和石灰剂量对无侧限抗压强度的影响。结果表明:浸水时长相同时,石灰改良黄土抗压强度随石灰剂量和压实系数的增大而增大;随着浸水时间的延长,石灰改良黄土7 d抗压强度先增高后降低,28 d强度持续降低;在相同浸水条件下,石灰剂量、压实系数的增大,均对石灰改良黄土抵抗长期浸水带来的负面影响有促进作用。

干湿循环作用下石灰土耐水性试验研究

为研究干湿循环条件下石灰土的水稳定性,对不同石灰掺量的石灰土试样进行干湿循环处理,开展无侧限抗压强度、密度和质量损失率试验,探究石灰土的强度和变形等物理力学性质。结果表明:石灰土在干湿循环作用下强度骤然降低,但随着干湿循环次数的增加强度有所提高并最终趋于稳定,长期干湿循环作用会使试样强度衰减37.58%~51.42%,但石灰掺量为15%时能有效抑制强度的衰减;石灰土在干湿循环作用下密度骤然增大16.94%~20.26%,初期表现出强烈的吸水特性,但随后密度不再增大;在干湿循环前期,石灰土试样会因土体内部火山灰作用和碳酸化作用而吸水,表现为石灰土质量先陡增后趋于稳定,反映出一定的抗水蚀性能;长期干湿循环作用下,试样破坏形态由脆性破坏转变为塑性破坏;建议在实际工程中将石灰土地基应用于干燥环境,采用15%的最优石灰掺量,即灰土体积比3∶7、含水率27.64%,以保证干湿循环对石灰土地基的水稳定性影响程度最小。