Properties and Mechanism of CFBC Fly Ash-cement based Stabilizers for Lake Sludge

Circulating fluidized bed combustion（CFBC） fly ash was mixed with cement or lime at a different ratio as a stabilizer to stabilize lake sludge.In order to understand the influences of stabilizers on the lake sludge properties,tests unconfined compressive strength,water stability and SEM observation were performed.The experimental results show that with the increase of the curing time,the strength of all the stabilized specimens increase,especially the samples containing cement.The strength of the specimens is decreased with the increasing of the CFBC fly ash/cement ratio,the optimum ratio between CFBC fly ash and cement is 2：3.The water stability of CFBC fly ash-cement based stabilizers is higher than those of cement and lime.Moreover,the lake sludge stabilization mechanism of CFBC fly ash-cement based stabilizers includes gelation and filling of the hydration products,i e,C-S-H gel and the AFt crystal,which act as benders to solidify those particles together and fill in the packing void of the aggregates.

Shrinkage and Expansive Strain of Concrete with Fly Ash and Expansive Agent

The effects of fly ash and MgO-type expansive agent on the shrinkage and expan-sive strain of concrete with high magnesia cement were investigated. The results show that high volumes of fly ash may reduce the shrinkage strain of concrete and inhibit the expansive strain of concrete with MgO-type expansive agent, but can not eliminate the shrinkage of concrete. MgO-type expansive agent may produce expansive strain and compensate the shrinkage strain of concrete, re-lieve the cracking risk, but the hydration product of magnesia tends to get together in paste and pro-duce expansive cracking of concrete with high magnesia content according to SEM observation.

Cement-fly Ash Stabilization of Cold In-place Recycled (CIR) Asphalt Pavement Mixtures for Road Bases or Subbases

For lack of laboratory and field performance data on stabilization of reclaimed asphalt pavement （RAP） aggregate and stabilized soil （S） for road bases and subbases construction, the influences of RAP/S ratio, cement and fly ash content, modifying agent （MA） on the compact, unconfined compressive strength, indirect tensile strength and water stability of the CIR mixtures were investigated. The experimental results showed that the maximum dry density and the optimum moisture content of the mixture changed significantly with the RAP/S ratio and cement-fly ash content. Unconfined compressive strength, indirect tensile strength and water stability were improved significantly by the addition of MA, and the water stability was improved by nearly 20% on average. Scanning electron microscopy（SEM） images indicated that MA accelerated the hydration of cement-fly ash system. Needle-like AFt and fibrous C-S-H gel were observed in the mixtures, which resulted in the cementation effect among the CIR mixture particles and a more compact microstructure. All these could be the cause of high strength of the CIR mixtures with MA.

Freeze-thaw performance of chemically stabilized natural and recycled highway materials

This article provides an overview of several previous studies that investigated the stiffness and strength performance of chemically stabilized roadway materials under winter conditions （freeze-thaw cycling）. The objective of this research was to understand the behavior of different materials stabilized with different type of binders when they were subjected to freeze-thaw cycling. Nine different materials including natural soils （organic soil, clay, silt, sand, and road surface gravel）, reclaimed pavement material, and recycled asphalt pavement stabilized with nine different binders （five different fly ashes, lime, cement, lime kiln dust, cement kiln dust） were discussed. This article investigated how the volume, resilient modulus and unconfined compressive strength of soils/materials stabilized with different binders change in response to freeze-thaw cycling. Overall, the review results indicate that the stiffness and strength of all stabilized materials decrease somewhat with freeze-thaw cycling. However, the reduced strength and stiffness of stabilized materials after freeze-thaw cycling was still higher than that of unstabilized-unfrozen original soils and materials. In addition, materials stabilized with cement kiln dust provided the best performance against freeze-thaw cycling.

Sustainable Fly Ash Based Roof Tiles with Waste Polythene Fibre: An Experimental Study

The compressive stress-strain behavior and other characteristics of treated fly ash based roof tiles have been studied by several experimental tests. This paper attempts to presents the results and observations of a study and comparison based on the past reported experimental data. Based on the results and observations of the comprehensive experimental study, five “control points” have been identified. The new sets of experiment have been carried out to investigate whether it might be possible the use of fly ash in fly ash based roof tiles for residential construction. In the present study, treated fly ash (TFA) of C category was used with different materials as a replacement of clay for making treated fly ash stone dust roof tiles (TFASDRT). Treated fly ash stone dust roof tiles (TFASDRT) were studied at varying percentages of cement, coarse sand, and radish stone dust (RSD) along with the constant percentage of waste polythene fibre (WPF). A research program was undertaken to evaluate the suitability of such test for assessing the properties of treated fly ash stone dust roof tiles (TFASDRT). The result of this study recommends that the fly ash based roof tiles provides a sustainable supplement to the traditional clay roof tiles, they increase the efficiency of traditional roof tiles and significantly help to reduce the environmental issues associated with the disposal of these waste materials.

激振搅拌对水泥稳定碎石与煤矸石抗压强度的影响

为研究激振搅拌工艺对水泥稳定煤矸石混合料性能的影响规律,以水泥稳定碎石为基准,对比分析普通搅拌与激振搅拌对不同水泥剂量的水泥稳定基层材料无侧限抗压强度的影响。结果表明:在干拌状态下增加激振工艺对基层混合料抗压强度的提升效果显著,在激振气压为0.4 MPa、激振干拌30 s后普通湿拌30 s条件下,混合料的7 d无侧限抗压强度达到最佳;激振搅拌对水泥稳定碎石、水泥稳定煤矸石混合料强度的平均提升幅度约为20%,对煤矸石混合料的强度提升更加显著,水泥剂量越少,提升幅度越大。SEM结果表明激振搅拌后混合料中的水化产物分布更加均匀,结构更加致密;经线性拟合计算,当水泥剂量为2.0%~7.0%(质量分数,下同)时,激振搅拌对于碎石混合料可节约8.9%~26.3%的水泥,对于煤矸石混合料可节约12.9%~30.8%水泥,且节约率与水泥剂量成反比。

公路路面基层施工中水泥稳定碎石技术的分析

随着国家交通基础设施建设的快速发展,对公路路面的施工质量要求日益提高。基层施工作为公路路面施工的重要组成部分,其施工质量直接关系到路面的整体性能和使用寿命。在众多基层施工技术中,水泥稳定碎石技术因其优异的性能和经济性得到了广泛应用。在实际应用中,应严格控制原材料质量,合理选择配合比,加强施工过程监控,确保工程质量达到设计要求。对公路路面基层施工中的水泥稳定碎石技术进行深入分析,以期为相关工程实践提供参考。

基于细观模型的水稳碎石抗温缩性能虚拟试验研究

水泥稳定碎石的温度收缩开裂问题长期以来未得到充分解决,其影响因素众多,在工程实践中难以确定具体改善措施。细观分析方法的发展为其提供了新的虚拟试验技术支持。以抗裂型水泥稳定碎石和普通水泥稳定碎石为对象,建立了基于内聚力单元的圆柱体试件模型,模拟单次降温条件,对不同级配参数和力学参数试件的抗温度收缩性能进行了对比研究。结果表明,采用零厚度内聚力单元的模型具有合理性,5种不同级配越接近连续级配、集料-砂浆界面和砂浆内部界面间黏结强度越大,水泥稳定碎石的抗温缩性能越差。为提高其抗温缩性能,应优先选择间断级配,并可采取适当措施降低集料和砂浆之间的黏结强度。

水泥稳定碎石基层双层连续摊铺层间性能影响因素分析

为分析水泥稳定碎石基层层间界面强度的影响因素,通过直接剪切试验和直接拉伸试验,对不同的水灰比及水泥浆剂量进行分析,得到层间最佳水泥浆剂量及水灰比。基于层间嵌挤接触咬合作用,分析了下层压实度及混合料级配对层间界面结合强度的影响。结果表明,当水泥浆撒布量为0.315g/cm 2、水灰比为1∶1.5时,层间粘结强度提升最大;下基层压实度为94%时摊铺上层,上、下层之间能形成良好的嵌挤结构;粗集料含量的增加可进一步提高上、下层之间的嵌挤作用,提高上、下层之间的约束作用。通过实体工程对室内试验结果进行验证,发现水灰比对水泥稳定碎石层间性能的影响更加显著。

水泥稳定钢渣碎石混合料性能研究

为确定钢渣替代部分石料应用于道路水稳基层的可行性,采用无侧限抗压强度、劈裂强度、抗压回弹模量、体积膨胀性和干缩试验等室内试验对水泥稳定钢渣碎石混合料的力学性能、稳定性能和干缩性能进行综合评定。结果表明:水泥稳定钢渣碎石混合料的无侧限抗压强度、劈裂强度和抗压回弹模量与对照组(不加钢渣)相比均有不同程度的提高;加入钢渣后水泥稳定碎石混合料的干缩系数变小,可减缓水泥稳定钢渣碎石基层的收缩变形;水泥稳定碎石钢渣混合料的浸水膨胀率满足规范要求。该研究成果对提升废弃钢渣在道路工程中的循环利用具有重要价值。

钢渣水泥稳定级配碎石混合料性能评价与应用

为将钢渣水泥稳定级配碎石应用于半刚性基层,分析20%~80%钢渣掺量对水泥稳定碎石力学性能(无侧限抗压强度、弯拉强度、动态回弹模量)、变形特性(干缩变形、温缩变形)、疲劳性能的影响规律,并基于室内研究成果铺筑试验段。结果表明:采用钢渣替代粗集料可增强水泥稳定级配碎石混合料的无侧限抗压强度、弯拉强度、动态回弹模量与抗疲劳耐久性能;增大钢渣掺量导致水泥稳定级配碎石温缩、干缩变形增大,以控制最大干缩系数不超过70~85με,以温度在-25~60℃区间内的平均温缩系数不大于12~15με/℃为限制条件,建议最大钢渣掺量为40%~60%;钢渣掺量40%的水泥稳定碎石基层试验段各指标,均满足相关设计、施工规范要求。

废旧橡胶粉对水泥稳定碎石基层力学及干缩性能的影响

为研究废旧橡胶粉对水泥稳定碎石基层混合料力学及干缩性能的影响,将不同粒径和掺量的橡胶粉以等质量等粒径的方式替换集料,通过考察劈裂强度、弯拉强度、抗压回弹模量和干缩试验研究了不同粒径和掺量的橡胶粉对水泥稳定碎石基层混合料力学及干缩性能的影响。结果表明,掺入橡胶粉降低了水泥稳定碎石基层混合料的劈裂强度、弯拉强度和抗压回弹模量,抑制了水泥稳定碎石的干燥收缩,且橡胶粉的粒径和掺量越大性能变化幅度越大。相较于不掺橡胶粉,掺入40目质量分数0.50%的橡胶粉时,水泥稳定碎石混合料90 d的劈裂强度、弯拉强度和抗压回弹模量分别降低了32.8%、51.0%和26.3%,累计干缩应变和干缩系数分别降低了27.4%和25.5%。

再生水泥稳定碎石基层力学性能研究

为改善再生水泥稳定碎石基层路用性能,本文依托实际工程对再生骨料水泥稳定碎石混合料力学性能进行研究。设计采用4种再生集料掺量(0%、25%、50%、75%),4种水泥掺量(3%、4%、5%、6%),分别进行击实试验、无侧限抗压强度和劈裂强度。研究结果得到,随着再生骨料掺量增加,最大干密度的降幅约为9.8%、9.7%、9.7%和9.6%,最佳含水率的增幅约为51.1%、48.9%、47.9%和46.9%;随水泥剂量增加,7d无侧限抗压强度由3.52MPa提升为6.10MPa,且90d劈裂强度为0.932MPa。再生水泥稳定碎石通过增强内部嵌挤力,提升了无侧限抗压强度和劈裂强度,使用铣刨料替代部分再生骨料,既优化了材料性能,又促进了资源的可持续利用。

新型水泥路面冷再生机组再生水泥稳定碎石试验研究

利用新型RH-S85旧水泥路面就地冷再生机组,采用铣刨、鄂破与反击破的综合方式完成废旧水泥混凝土面板二次破碎,解决了传统单次方法破碎颗粒度较大的问题。通过筛分级配、无侧限抗压强度等试验,研究了破碎再生集料的级配特征以及再生水泥稳定碎石混合料强度特性。结果表明:经RH-S85机组二次铣刨后的再生集料,大部分粒径级配处于规范的上下限范围内,但φ0.6 mm以下的细集料数量偏多,超出了级配上限,经调整后符合规范要求。随着水泥含量的增加,再生集料形成的水泥稳定碎石混合料的最大干密度呈线性增加,最佳含水量呈对数增加,无侧限抗压强度呈指数递增。控制适量水泥剂量情况下,利用RH-S85机组再生集料制备的再生水泥稳定碎石混合料强度符合各类交通条件的规范要求,可有效实现节约环保目的。

水泥稳定级配碎石基层施工技术要点

临洮(安家咀)至临夏公路工程中,采用为水泥稳定级配碎石作为基层,其工程量为88549.2 m^(3)。为保证基层施工质量,重点对多工序进行质量控制。

掺加细粒风化料的水泥稳定碎石级配优化设计方法

以碎石粗集料形成骨架结构、细粒风化料与水泥作为细料填充骨架空隙的矿料体积组成模型,提出了基于细料用量理论公式的骨架密实型级配优化设计方法,并进行了应用及验证。结果表明:优化设计的骨架密实型级配2^(#)的混合料具有最小的间隙率,密实程度最大,是实际意义上的骨架密实结构。级配2^(#)的7 d无侧限抗压强度最高,比级配3^(#)、4^(#)分别高19.1%、7.9%,符合高等级公路重交通的基层强度要求;其抗拉强度比级配3^(#)高16.4%,仅比级配4^(#)低6.6%。验证表明了级配优化设计方法是可行且合理的。

大厚度水泥稳定碎石半刚性基层一次性摊铺施工技术

以实际工程项目为例,探讨大厚度水泥稳定碎石半刚性基层一次性摊铺施工技术的应用和施工技术,并设计室内试验确定混合料最佳配合比,根据一次性摊铺施工技术的特点和工程项目的具体设计要求,严格控制材料施工质量,加强施工技术的应用质量及机械配备,确保基层结构的安全稳定性。

高速公路沥青路面预防性养护技术的应用

本文主要探究了某高速公路沥青路面的病害处置和预防性养护技术。从现场检测情况看,该路段主要有坑槽、翻浆、横纵裂缝和龟裂四种病害。对于坑槽集中分布以及轻度龟裂的路段,铣刨路面直至露出路基,清理基层后回补AC-25改性沥青混凝土和微表处;对于存在翻浆、横纵裂缝以及重度龟裂的路段,铣刨路面后再铣刨路基上层。路基上层用水泥稳定碎石回补,路面回补AC-25改性沥青混凝土和微表处。在病害处置时,通过严格控制沥青混合料、微表处混合料以及聚酯纤波波等材料的质量,切实提高了沥青路面病害的处置效果,达到保证行车安全和延长公路寿命的效果。

低温条件下水泥稳定碎石基层施工技术研究

为改善寒冷地区半刚性基层的使用性能,保证工程质量,论文以实际项目为依托,分析水泥稳定碎石的原材料选择与级配设计,并通过击实试验和无侧限抗压强度试验确定水泥和早强剂的剂量,总结各环节的施工要点。

钢渣在水泥稳定碎石基层中的应用研究

为应对我国公路建设中原材料匮乏和公路基层抗裂性问题,论文对钢渣的物理力学性质进行测试,检测5种钢渣掺量的水泥稳定碎石混合料的无侧限抗压强度、间接抗拉强度、抗压回弹模量等性能指标,并对其在道路路基中取代碎石的可能性进行分析。研究结果表明:在水泥稳定碎石中加入钢渣可以代替部分碎石,其力学性质随钢渣量的增加而有规律地改变。