水泥-废石膏加固软土的试验研究

利用废石膏和水泥配合加固软土，与单纯用水泥加固相比，可显著提高加固效果。在水泥－废石膏的水化物中，既有水泥产生的水化硅酸钙胶结松散的土颗粒，又有水泥与石膏产生的钙矾石膨胀填充孔隙。加固土孔隙水中ＣａＯ，ＯＨ－浓度决定水泥－废石膏的适用性及其增强效果。     

利用磷石膏加固软土地基的工程实例

工程实践表明，与单纯用水泥加固相比，用磷石膏与水泥配合加固软土地基可大幅度提高加固土强度，且拓宽了水泥加固技术适用的土质条件范围，技术、经济和环境效益显著。对不同的土质，磷石膏的增强效果差异很大。在多土层地基施工时，应注意固化剂配合比对各土层的适用性。采用正确的加固土强度试验方法才能得到对磷石膏增强效果的正确评价。     

工业废石膏在地基加固中的应用

试验研究和工程实践表明，利用工业废石膏与水泥配制的水泥－废石膏固化剂具有较好的技术经济效益和社会效益．本文概要介绍了水泥－废石膏固化剂的加固效果、加固机理、影响其加固效果的诸因素及工程实例．     

石膏添加剂对水泥土搅拌法加固软土地基效果影响的微观试验分析

采用水泥土搅拌法加固软土地基时,在固化材料中加入石膏添加剂能够提高水泥加固土的强度。针对这种现象,结合某水泥土搅拌法软土地基加固工程,从化学成分与物理结构等微观角度出发,分别对原状土、含石膏水泥加固土、不含石膏水泥加固土土样进行了XRD、SEM等两种微结构试验,对比分析了导致这种加固效果差异的微观机理及形成原因。研究结果显示,含石膏与不含石膏的水泥加固土在水化反应程度与物理微结构方面均存在着较为显著的差异,并导致了加固土体宏观强度表现上的不同。因此,在类似地基加固工程中可考虑向固化材料中加入适当掺量的石膏添加剂,以改善加固土体的微观结构特征,优化地基加固效果。     

有机质含量对水泥土强度的影响与对策

通过两种不同有机质含量的软土,采用水泥和磷石膏、粉煤灰固化剂加固土强度对比试验,讨论了有机质、水泥、磷石膏、粉煤灰对加固土强度影响机理,提出了抵抗明机质含量对水泥土强度影响的措施。     

含工业废料的水泥系固化剂加固软土试验研究

在水泥中掺适当的工业废料做加固土的固化剂 ,不仅可以节约工程造价 ,而且可以增加加固土的强度。本文从机理探讨 ,室内加固土强度试验和室外静载试验三方面研究分析了水泥中掺工业废料粉煤灰和磷石膏加固软土的可行性和实用性。     

深层搅拌桩复合地基设计施工的探讨

1、设计步骤及相应参数的获取 水泥与软土采用机械搅拌加固的原理,是基于水泥和土的物理化学反应过程,水泥作为固化剂是提高软土强度的主要因素,它与混凝土的硬化机理有所不同,混凝土的硬化主要是水泥在祖填充料中进行水解和水化作用,因而强度发挥快。而在水泥加固土中,水泥的水解和水化反应是与具有一定活性的介质土进行的,所以凝     

工业废料合成固化剂加固土的室内试验研究

利用工业废料加固地基具有较好的技术经济效益和社会效益，本文概要介绍水泥-粉煤灰、水泥-磷石膏固化剂加固土的室内试验研究。     

两重管高压旋喷桩在泥炭土地基加固中的应用

在水泥加固地基土的基础上,结合高有机质泥炭土的特性,分别采用黏土浆液改良后施作两重管高压旋喷加固、水泥-石膏浆液改良后施作两重管高压旋喷加固及直接施作旋喷桩加固三种方案进行现场试桩,结果发现:水泥-石膏浆液改良后施作两重管高压旋喷加固土芯样完整呈柱状,胶结性好,抗压强度达1 MPa以上固化效果最好,黏土浆液改良后施作两...     

一种新型的软土地基固化剂——水泥-废石膏固化剂

<正> 有些软土地基加固方法,如深层搅拌法、旋喷法、水泥拌合土法等,其加固过程是以不同的方式将固化剂与软土拌和,利用固化剂与软土之间发生的物理化学反应,使软土硬化成为具有足够强度的固化土,从而达到地基加固的目的。拟加固的软土,一般都因孔隙率高、土颗粒间联系松散而强度低下。显然欲将这类软土加固成具有足够强度的固化土,理想的固化剂应当同时具有胶结松散土颗粒和填充土体中孔隙的两重作用。以     

Durability of soft clay soil stabilized with recycled Bassanite and furnace cement mixtures

This study examines the wetting–drying durability of soft clay soil stabilized with recycled Bassanite, produced from gypsum waste. Specifically, this study focuses on an investigation of the effects of the moisture conditions on the strength performance and durability of very soft clay soil stabilized with Bassanite and furnace cement mixtures during the wetting–drying cycles, referred to as weathering conditions in this study. Cylindrical stabilized soil specimens were produced and then cured for 28 days. The cured specimens were subjected to different numbers of wetting–drying cycles, and then tested for unconfined compressive strength. The results show that the compressive strength increased with an increase in the Bassanite content for the different wetting–drying cycles investigated. The increase in the Bassanite content is associated with the increase in the dry unit weight, as well as in the decrease in the moisture content of the stabilized specimens for the different wetting–drying cycles investigated. The compressive strength of the soil stabilized with the Bassanite and furnace cement mixtures gradually decreases with an increase in the number of wetting–drying cycles, and the earlier cycles are seen to have a more negative effect on durability than the later cycles. Generally, the influence of the wetting–drying cycles on changes in the strength, durability and volume of the soft clay soil stabilized with Bassanite and furnace cement mixtures is not significant. This is evidence that the use of recycled Bassanite, produced from gypsum waste to stabilize soft clay soil, achieves acceptable durability, raises the strength performance and improves the engineering properties of soft clay soil in a wet environment. In addition, the effective use of gypsum waste contributes to the development of a sustainable society by reducing the huge quantity of solid waste and establishing a sound environment.     

Laboratory and Field Evaluations of Recycled Gypsum as a Stabilizer Agent in Embankment Construction

Approximately 1.6 million tons of gypsum waste plasterboard are produced annually in Japan. As such, it is essential to find an alternative way to reduce the quantities of this waste material to avoid environmental problems and the high cost of disposal in landfill. This paper describes a case study focused on the use of recycled gypsum, which is derived from gypsum waste plasterboard, to improve the strength of soft clay soil for embankment construction projects taken in consideration environmental impacts. Four different recycled gypsum contents ranging from 0 to 10% was investigated. Two different types of cements—Portland and Furnace slag type B—with a content ranging from 0 to 3% was used to develop solidification for recycled gypsum and improve environmental properties. For this purpose, a series of unconfined compression tests were conducted to evaluate strength performance of treated clay. While a series of environmental tests were conducted to explore the solubility concentration of fluorine, boron, and hexavalent chromium in the untreated and treated soil specimens. Furthermore, hydrogen sulfide and pH were investigated. Results showed that compressive strength and unit weight of treated clay soil increased with the increase of recycled gypsum content. The strength obtained in the field for treated soil with recycled gypsum was found to be greater than that obtained in the laboratory. The early curing days for soil-gypsum mixture had a significant effect on strength performance compared to the later days. The additives of recycled gypsum for tested soil swiftly increased the strength. This is a vital property for improvement embankment trafficability that helps to reduce the construction time and cost. The use of recycled gypsum within the investigated limits had no adverse effect on pH value and hydrogen sulfide gas was found to be less than the standard permitted limits. As well, the solubility concentrations for fluorine, boron, and hexavalent chromium were found within the permitted standard limits in Japan. The curing time had a significant effect on the reduction the release of harmful substance elements investigated. Furnace cement type B had the potential to improve the mechanical and environmental functions for soil-gypsum mixture. It is recommended that Furnace cement type B be used as a solidification agent for soil treated with recycled gypsum because it has low cost and it is more environmentally friendly than Portland cement.     

Investigation of recycled gypsum in conjunction with waste plastic trays for ground improvement

During the three stages of production, construction and demolition, approximately 15 million tons of gypsum waste plasterboard is generated annually in the world. It is considered a serious problem due to scarcity of land-filling space, increasing the cost of disposal and increasing environmental regulations. Investigations of using recycled gypsum “bassanite” which is derived from gypsum waste plasterboard and waste plastic trays for ground improvement were studied. Recycled gypsum was used as a stabilizing agent to improve the compressive strength while the waste plastic trays were used to improve the tensile strength. Recycled gypsum content, curing time and frost heave property throughout capillary rise test were investigated to determine the behavior of treated soil with recycled gypsum. In addition, size, content and aspect ratio of strips of waste plastic trays were investigated. Test results showed that increasing recycled gypsum content has a more significant effect on compressive strength compared to the tensile strength. The effect of curing time on the strength of treated soil samples with recycled gypsum is much pronounced in the early curing days compared to later ages. Adding strips of waste plastic trays to samples treated with recycled gypsum enhanced both splitting tensile and compressive strengths as well increased the value of secant modulus. Capillary rise rate was reduced with the increase of recycled gypsum content, which helps to reduce the formation of ice lenses; hence the susceptibility of treated soil against frost heave is increased. The size and content of strips of waste plastic trays have significant effect on the potential of capillary rise and the enhancement of strength and stiffness of tested soil.     

新型固化剂GSC固化软土的力学性能试验研究

利用脱硫石膏及钢渣-矿渣复合胶凝材料(简称GSC)固化软土,既可以充分利用工业废渣,减少二次污染,又可以节约矿产资源,保护自然生态.通过研究在不同掺入比、不同水灰比和不同龄期时GSC固化土的无侧限抗压强度试验结果,分析了掺入比、水灰比、龄期对固化土强度的影响;同时引入似水灰比对GSC固化土后期强度进行预测.研究结果表明,GSC掺入比越大,对软土的固化效果越好,GSC固化土无侧限抗压强度随龄期的增长规律与水泥土一致但早期强度比水泥土低,当GSC掺入比高于水泥掺入比3％,在龄期达到28 d后,如果GSC的水灰比小于水泥的水灰比时,GSC固化土的强度高于水泥土的强度,因此用GSC替代水泥作为软土固化剂可以满足固化土强度要求.     

软土地基生石膏浅层搅拌加固技术

利用SEM试验及强度试验,从微观上研究了生石膏掺量对有机质软土固化效果的影响,分析了固化剂中生石膏的最佳掺量,指出采用生石膏与水泥组成的新型固化剂加固软基可提高固化土强度,达到节约水泥、降低成本的目的。     

发泡磷石膏墙体材料配合比及其性能试验研究

以废弃磷石膏为主要原材料研制一种发泡磷石膏新型墙体材料,分别研究了水泥、矿粉、发泡剂和缓凝剂对磷石膏性能的影响;利用正交试验系统地分析水料比、发泡剂、矿粉和水泥对发泡石膏材料抗压强度、干密度和吸水率等性能的影响,并以抗压强度和干密度为主要指标得到发泡石膏材料的最佳试验配合比为水料比0.5、发泡剂掺量0.9%、矿粉掺量6%、水泥掺量10%。     

利用工业废渣—氟石膏代替天然石膏做矿渣水泥缓凝剂试验

通过对工业废渣-氟石膏做缓凝剂试验与天然石膏相比,具有相同的缓凝作用。同时对矿渣水泥有一定的激发作用,增进水泥强度。通过试验,我们认为可以利用工业废渣-氟石膏做水泥缓凝剂,从而降低水泥成本,同时具有可观的经济效益和明显的社会效益。