温州软土水泥土抗压强度与养护龄期、水泥掺合量的关系

本文通过温州粘土、淤泥质粘土和水泥混合产生的水泥土的室内抗压强度试验,找到了水泥土抗压强度与水泥掺量、养护龄期三者的相关性(经验公式),对水泥深层搅拌法的应用具有一定的指导作用。

土的可塑性对水泥土无侧限抗压强度的影响浅析

水泥土深层搅拌桩法是常用的软土地基处理方法之一,广泛的应用于高速公路软土地基处理中。水泥土室内配合比试验是搅拌桩设计和施工前的一项重要的内容。通过水泥土室内配合比试验,得出水泥土无侧限抗压强度与软土的塑性指标之间的关系,并提出对水泥土强度问题的一些看法。

水泥土力学性质试验研究

通过比较焦作市某工程软地基土不同含水量,不同水泥、粉煤灰掺量的试件不同龄期的无侧限抗压强度,分析了含水量、水泥掺量、粉煤灰掺量和龄期对试件强度的影响,得出了水泥掺量、粉煤灰掺量和标准龄期的最优值。

浅谈水泥深层搅拌加固土物理力学影响因素

本文通过实例对影响水泥土力学性质的各种因素进行分析,陈述了水泥掺入比、龄期、水泥种类、原土情况、养护条件及外掺剂对水泥土强度的影响。

董洼水库大坝防渗加固评价

本文通过董洼水库工程地质条件的分析,大坝采用多头小直径防渗墙垂直防渗措施,并结合工程竣工检测数据和运行效果,对董洼水库大坝防渗效果进行综合评价。

大直径劲性搅拌桩承载力试验研究

劲性搅拌桩是一种将PHC管桩插入水泥土中形成协同受力的桩型。在天津市汉沽区某工业园区场地内进行了大直径等长芯劲性搅拌桩单桩竖向承载力试验,并和相同直径灌注桩做了对比。试验结果表明,劲性搅拌桩成桩质量好,水泥土取芯单轴抗压强度高,可以为管桩-水泥土内界面提供足够的抗剪强度。大直径劲性搅拌桩极限承载力、单桩总侧阻力、端承阻力和同直径灌注桩相比均有大幅度提升,短劲性搅拌桩的端承比例更大且端阻发挥的时机更早。和同直径的灌注桩比,劲性搅拌桩提供相同的承载力所需的桩身长度大幅度减少,降低单位承载力造价。

Strength of copolymer grouting material based on orthogonal experiment

Using the orthogonal experimental design method involving three factors and three levels, the flexural strength and the compressive strength of copolymer grouting material were studied with different compositions of water-cement ratio （mass fraction of water to cement）, epoxy resin content, and waterborne epoxy curing agent content. By orthogonal range and variance analysis, the orders of three factors to influence the strength, the significance levels of different factors, and the optimized compound ratio scheme of copolymer grouting material mixture at different curing ages were determined. An empirical relationship among the strength of copolymer grouting material, the water-cement ratio, the epoxy resin content, and the waterborne epoxy curing agent content was established by multivariate regression analysis. The results indicate that water-cement ratio is the most principal and significant influencing factor on the strength. Epoxy resin content and waterbome epoxy curing agent content also have a significant influence on the strength. But epoxy resin content has a greater influence on the 7-day and 28-day flexural strength, and waterborne epoxy curing agent content has a greater influence on the 3-day flexural strength and the compressive strength. The copolymer grouting material with water-cement ratio of 0.4, epoxy resin content of 8% （mass fraction） and waterbome epoxy curing agent content of 2% （mass fraction） is the best one for repairing of cement concrete pavement. The flexural strength and the compressive strength have good correlation, and the ratio of compressive strength to flexural strength is between 1.0 and 3.3.

Strength characteristics of modified polypropylene fiber and cement-reinforced loess

The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials.To study the strength characteristics of loess soil reinforced by modified polypropylene(MPP) fiber and cement,samples were prepared with six different fiber contents,three different cement contents,three different curing periods and three kinds of fiber length.The samples were tested under submergence and non-submergence conditions for the unconfined compressive strength(UCS),the splitting tensile strength and the compressive resilient modulus.The results indicated that combined reinforcement by PP fiber and cement could significantly improve the early strength of loess to 3.65–5.99 MPa in three days.With an increase in cement content,the specimens exhibited brittle fracture.However,the addition of fibers gradually modified the mode of fracture from brittle to ductile to plastic.The optimal dosage of fiber to reinforce loess was in the range of 0.3%–0.45% and the optimum fiber length was 12 mm,for which the unconfined compressive strength and tensile strength reached their maxima.Based on the analysis of failure properties,cement-reinforced loess specimens were susceptible to brittle damage under pressure,and the effect of modified polypropylene fiber as the connecting "bridge" could help the specimens achieve a satisfactory level of ductility when under pressure.

Study on influence factors of cement-stabilized soil compressive strength

The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.

Assessment of strength development in cement-admixed artificial organic soil with GX07

To explore the stabilization effect of stabilizing agent GX07 on treating organic soil and the influence of organic matter on the strength development of stabilized soil,artificial organic soil with various organic matter content was obtained by adding different amounts of fulvic acid into non-organic clay,and then liquid-plastic limit tests were carried out on the artificial organic soil.Meanwhile,unconfined compressive strength(UCS) tests were performed on cement-only soil and composite stabilized soil,respectively.The test results indicate that the plastic limit of soil samples increases linearly,and the liquid limit increases exponentially as the organic matter content increases.The strength of stabilized soil is well correlated with the organic matter content,cement content,stabilizing agent content and curing time.When the organic matter content is 6%,as the cement content varies in the range of 10%-20%,the strength of cement-only soil increases from 88.5 to 280.8 kPa.Once 12.6% GX07 is added into the mix,the strength of stabilized soil is 4.93 times compared with that of cement-only soil.GX07 can obviously improve the strength of cemented-soil and has a good economic applicability.A strength model is proposed to predict strength development.

High-Volume Fly Ash Concrete-A Relevant Step to Sustainable Development

HVFA （high-volume fly ash） concrete could be a sustainable way for by-product utilization to conserve natural resources and protect environment. HVFA concrete can play the role of a high-performance material that may be comparable to the conventional Portland cement concrete. The results of the research programme concerning the relationships between the composition of concrete （w/b ratio, fly ash content and type of cement） and their physical and mechanical properties are presented and discussed in the paper. It is found that the introduction of high-volume fly ash into concrete has caused a decrease in compressive strength at the early age of storage. The significant increase in strength was observed between 28 days and 90 days of curing. The high-volume fly ash concretes were characterized with lower water absorbability and sorptivity than control concrete.

Production and Properties of Superplasticized Concrete

The objective of this research is to study the effect of grinding powdered superplasticizer, Portland cement, sand, and silica fume on the properties of fresh and hardened concrete. Lose Angeles Machine was used to grind these constituents. The program was arranged to determine the effect of cycles＇ number, superplasticizer type and dosage, silica fume dosage and condition, and gravel to sand ratio on properties of concrete. Naphthalene sulphonated formaldehyde （NSF） superplasticizers in the forms of liquid and powdered were used. Silica fume may be grinded with the other constituents （grinded）, or added to concrete mixer （normal）. The water/cement （w/c） ratio varied from 0.35 to 0.55 to achieve a constant slump （50-90 mm）. Slumps, bulk density and mechanical properties of concrete were measured. Scanning electron microscope （SEM） was also used to show the differences between traditional and superplasticized concrete. The results showed that grinding the mixture enhances fresh and hardened concrete properties. It is also observed that grinding the mixture for 500 cycles is more effective than other numbers of grinding. In addition, superplasticized concrete exhibits compressive strength higher than traditional one at varied ages. Moreover, using powdered superplasticizer has a remarkable effect on enhancing concrete properties rather than using it in a liquid form. A dosage of 1% by weight of cement gave the highest results of compressive strength. Silica fume has an essential role in improving concrete strength and durability since it acts as very efficient void filler and as a super pozzolana. SEM observations illustrate that grinding the mixture enhances transition zone （TZ） properties and makes it denser. On the other hand, grinded mixture can be packaged in bags and transported for use in crowded cities, and so, enhances quality control, since the only requirement to obtain superplasticized concrete is to add water and gravel. This technique has many benefits such as; saving cement, labor and noise, high quality control, and enhancing concrete permeability and durability. There are many fields of application of superplasticized concrete such as; in locations which are not easily accessible by ordinary concreting techniques, in repairing and strengthen, thin coating, and for small projects when ready mix supply is not feasible.