Soilcrete blocks

This paper presents research conducted to determine the relationship between compaction pressure, cement content and cured compressive strength for soilcrete building blocks (soil-cement, cement stabilized or sandcrete). This relation is then used as the basis for a simple economic model to evaluate the economics of manual compaction to 2 and 10 MPa. Other authors have shown that higher compressive strengths result from increased compaction pressure. However, for a given compressive strength it is more usual to be interested in trading increased compaction pressure for reduced cement content so that maximum economy is achieved. This paper describes experimental work carried out to determine an empirical relation which uses compaction pressure and cement content to define cured strength. The relationship presented in this paper suggests that cured strength is more dependent on cement content than it is on compaction pressure for a well-cured block. The economic model suggests that low pressure manual compaction using increased quantities of cement is a more economic method of block production unless the cost of high pressure compaction machinery can be reduced. Cet expose presente les travaux de recherche conduits en vue de determiner la relation optimale entre pression de compactage, teneur en ciment et resistance a la compression a l'etat durci des parpaings de terre agglomerec (terre-ciment, ciment stabilise ou sable agglomere). Cette relation est ensuite utilisee sur la base d'un modele economique simple, afin d'evaluer l'aspect economique d'un compactage manuel a 2 et 10 MPa. D'autres auteurs ont montre que de plus hautes resistances a la compression s'obtenaient par augmentation de la pression de compactage. Cependant, pour une valeur donnee de resistance a la compression, il est plus courant, d'un point de vue commercial, de preconiser une pression de compactage accrue pour une teneur en ciment reduite. Cet expose decrit les travaux experimentaux effectues pour determiner une relation empirique faisant appel a la pression de compactage et a la teneu en ciment pour definir la resistance a l'etat durci. La relation presentee dans cet expose donne a penser que la resistance a l'etat durci depend davantage de la teneur en ciment que de la pression de compactage pour un parpaing bion durci. Le modele economique amene a conclure qu'un compactage manuel a faible pression associe a des teneurs accrues en ciment offre un procede de fabrication des parpaings plus economique qu'un compactage a haute pression associe a de faibles teneurs en ciment.     

Modeling of hydration kinetics in cement based materials considering the effects of curing temperature and applied pressure

Portland cement is the most widely used cement in the world. In the industrial by-products suitable for use as mineral admixtures in Portland concrete are ashes produced from the combustion of coal and granulated slag in metal industries. However, comparing such ashes with Portland cement, determining the hydration of this concrete is much more complex because of the reaction between calcium hydroxide and fly ash or slag. In this paper, the production of calcium hydroxide in cement hydration and its consumption in the reaction of mineral admixtures are considered in order to develop a numerical model for simulating the hydration of concrete, which contains fly ash or slag. The proposed numerical model includes the effects of water to binder ratios, slag or fly ash replacement ratios, curing temperature, and applied pressure. The heat evolution rate of fly ash- or slag-blended concrete is determined by the contribution of both cement hydration and the reaction of mineral admixtures. Furthermore, an adiabatic temperature rise in hardened blended concrete is evaluated based on the degree of hydration of the cement and mineral admixtures. The proposed model is verified through experimental data obtained from the concrete with different water-to-cement ratios and mineral admixture substitution ratios at elevated temperature and high pressure.     

强夯处理湿陷性黄土地基工程特性浅析

结合豫西某电厂湿陷性黄土地基强夯处理工程实践,分析处理前后土层的工程特性,结果表明,采用强夯处理不同性质的湿陷性黄土,产生的处理效果不同,可为类似工程提供借鉴。     

张河湾电站上水库坝体垫层料碾压试验研究

水库坝体垫层料的压实质量是控制坝体稳定、沉降变形和防止面板裂缝的关键,为保证张河湾水库坝体垫层料的质量,施工前需进行垫层料的现场碾压试验。通过现场碾压试验,了解影响垫层料压实质量的因素,确定最佳碾压参数,为坝体垫层料的施工提供了科学依据。     

孔内深层强夯法在湿陷性黄土中的应用研究

结合工作实践经验,对孔内深层强夯法在湿陷性黄土地基处理中的应用进行了探讨,并将其与强夯法和普通灰土桩进行了对比分析,得出采用孔内深层强夯法处理地基可获得较好的挤密效果,经济效益显著的结论。     

CFG桩复合地基设计的工程应用

CFG桩复合地基是由CFG桩、桩间土和褥垫层一起构成的刚性桩复合地基。通过褥垫层把桩和基础断开,改变了过分依赖桩承担垂直荷载和水平荷载的传统设计思想,其优点体现在其传递水平荷载和垂直荷载的工作特性上。CFG桩复合地基设计,必须同时满足强度和变形两个条件。CFG桩复合地基技术以其用材经济、施工快捷、加固效果良好等优点,在工程上得到了广泛的应用。     

分散剂对碳纤维水泥砂浆力学性能及压敏性的影响研究

研究了分散剂的种类(HPMC、MC、HEC)和掺量(0、0.2%、0.4%)对碳纤维水泥砂浆(CFRM)力学性能和压敏性的影响。结果表明:当分散剂掺量为0.2%时,掺HPMC和MC的CFRM试件抗压、抗折强度均高于基准组,其中,HPMC对力学性能的提升效果最好;各组试件的电阻变化率均随着应力的增大而减小,其中,HPMC掺量为0.2%的试件灵敏度最高。综合考虑,采用0.2%的HPMC时,CFRM的力学性能和压敏性达到最佳。     

灌注桩底的水泥土桩在三轴受力状态下的承载力分析

本文结合某工程人工挖孔灌注桩桩底旋喷水泥土桩的静载试验结果 ,分析灌注桩桩底旋喷水泥土桩 ,由于桩侧土层自重在桩周产生的侧压力 ,使旋喷水泥土桩处于三轴受力状态下的承载力情况 ,供设计与施工参考     

Application of phosphogypsum in soil stabilization

This paper describes the application of phosphogypsum with cement and fly ash for soil stabilization. Atterberg limits, standard Proctor compaction and unconfined compressive strength tests were carried out on cement, fly ash and phosphogypsum stabilized soil samples. Treatment with cement, fly ash and phosphogypsum generally reduces the plasticity index. The maximum dry unit weights increase as cement and phosphogypsum contents increase, but decrease as fly ash content increases. Generally optimum moisture contents of the stabilized soil samples decrease with addition of cement, fly ash and phosphogypsum. Unconfined compressive strengths of untreated soils were in all cases lower than that for treated soils. The cement content has a significantly higher influence than the fly ash content. The use of two waste by-products, phosphogypsum and fly ash may provide an inexpensive and advantageous construction product.     

Effect of fiber-reinforcement on the strength of cemented soils

This study aims to verify the differences in the strength of an artificially cemented sandy soil with and without fiber reinforcement. The controlling parameters evaluated were the amount of cement, porosity, moisture content, and voids/cement ratio. A series of unconfined compression tests and suction measures were carried out. The results show that fiber insertion in the cemented soil, for the whole range of cement studied, causes an increase in unconfined compression strength. The UCS increased linearly with the amount of cement and reduced with the increase in porosity (η) for both the fiber-reinforced and unreinforced specimens. A power function fits well as the relation between unconfined compressive strength (UCS) and porosity (η). Finally, it was shown that the voids/cement ratio is a good parameter in the evaluation of the unconfined compressive strength of the fiber-reinforced and unreinforced cemented soil studied.     

共振碎石化技术在水泥混凝土路面改造工程中的应用

本文介绍了共振碎石化技术在福州市东二环路面改造工程中的应用情况,阐述了共振原理、施工工艺流程、施工技术要点以及质量控制标准,为其他工程项目提供经验参考。     

Elastic wave velocities and permeability evolution during compaction of Bleurswiller sandstone

Field observations and laboratory experiments have recently documented the formation of compaction bands in porous sandstones [Mollema and Antonellini, Tectonophysics 1996;267:209–28; Olsson and Holcomb, Geophys Res Lett 2000;27:3537–40; Bésuelle, J Geophys Res 2001;106:13435–42; Klein et al., Phys Chem Earth 2001;26:21–5]. It has been observed experimentally [Wong et al., J Geophys Res 2001;28:2521–4; Baud et al., J Geophys Res 2003, submitted; Fortin et al., 2003, Abstract EGS-AGU Nice] that under axisymmetric compression, compaction bands develop sub-perpendicular to the main compressive stress which is predicted theoretically in the framework of strain localization theory [Bésuelle, J Geophys Res 2001;106:13435–42; Issen and Rudnicki, J Geophys Res 2000;105:21529–36]. Volumetric strain, fluid transport and elastic properties are intimately coupled to one another, for they all depend on a few intrinsic parameters such as the porosity, the crack density, and the matrix and fluid elastic properties. On the one hand, Scott et al. [Rock Mech Min Sci Geomech 1993;30:763–9] showed that elastic wave velocities were clearly affected during the deformation of porous sandstones. On the other hand, Zhu and Wong [J Geophys Res 1997;102:3027–41] showed that the relation between the evolution of permeability and volumetric strain during compaction of sandstones was not straightforward. In this study, we present for the first time the simultaneous evolution of volumetric strain, elastic wave velocities and permeability for a set of deformation experiments of Bleurswiller sandstone. We show that, although very coherent to one another, those three sets are not systematically correlated. Indeed, inelastic compaction, whether it is distributed or localized, is accompanied by a drastic decrease of elastic wave velocities due to grain crushing, a decrease of permeability and porosity due to pore collapse. Using simple statistical physics concepts based on the study of Kachanov [Adv Appl Mech 1993;30:259–445] and Guéguen and Dienes [Math Geol 1989;21:1–13], we try to understand and address the issue of coupling/decoupling between volumetric strain (mainly sensitive to equant porosity variations), elastic properties (mainly sensitive to crack density) and permeability (theoretically sensitive to both) during the formation of compaction bands. Finally, we show that the mineral composition of a sandstone is a key parameter controlling the effective pressure at which the onset of pore collapse P^* takes place.     

高压旋喷桩在深厚软土基础处理中的应用

通过高压旋喷桩和水泥搅拌桩在深厚软土地基处理中的成桩质量的比较,介绍高压旋喷桩技术在软土基础处理中的应用。     

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.     

粉煤灰在公路水泥砼路面中的应用

针对在公路水泥砼路面的砼混合料中掺入一定用量的粉煤灰对混合料的性能具有改善作用，从粉煤灰砼的配合比设计、工程实用效果、可能存在的质量缺陷及其处理方法、可观的社会经济效益等方面做一些分析。     

水泥土固化剂在建筑垃圾砌块中的应用

我国建筑垃圾的数量已经占到城市垃圾总量的30％-40％。未经处理的建筑垃圾,不仅占用了大量的土地和建设经费,也污染了地表环境和地下水。实现建筑垃圾的再利用,有利于环境保护,符合循环经济发展国策。利用水泥土固化剂生产各类建筑垃圾砌块具有方便、经济、质量好的优点。     

锡尾矿制备水泥砂浆的研究与应用

分析了锡尾矿替代河砂用于制备水泥砂浆的可行性,探索了锡尾矿替代量对水泥砂浆工作性和力学性能的影响规律。结果表明:随锡尾矿替代量的增加,水泥砂浆的保水率、黏结强度、抗压强度逐渐降低,分层度和Cl-扩散系数逐渐升高,干燥收缩值先增加后趋于稳定;当锡尾矿替量低于20%时,锡尾矿水泥砂浆各性能均符合标准要求。所制备的水泥砂浆强度等级达到M7.5,可作为砌筑砂浆和抹面砂浆应用于各种建筑之中。     

上覆吹填砂原料场地基强夯试验研究

试验采用插塑料排水板+强夯的施工工艺,监测了夯坑及夯坑周边土体的沉降和隆起以及孔隙水的变化情况,分析了强夯加固范围和深度、孔隙水的消散时间以及最佳夯击次数,通过静载荷试验及双桥静力触探试验对强夯加固效果进行检验。     

轻便触探检测水泥土搅拌桩浅谈

水泥土搅拌桩作为一种地基处理技术,正在被广泛的应用,但是,在如何采用轻便触探来判定搅拌桩的桩身强度及成桩均匀性等方面,相关的规范没有可操作性标准。本文结合规范及工程实际情况,提出了轻便触探击数N10与强度对应关系、不同水泥土龄期所对应的轻便触探击数及成桩均匀判定标准等,因此,使之真正具有可操作性的一种检测手段。