Microstructure and Properties of Silty Siliceous Crushed Stone-lime Aerated Concrete

The clayish crushed stone was used for making aerated concrete. Through studying hydro-thermal synthesis reaction, mix ratio, gas-forming and performance analysis, Grade-B05 and Grade-B06 aerated concrete were prepared successfully. The proper mix ratio and key processing parameters were achieved. The microstructure of aerated concrete with crush stone was analyzed by means of XRD and SEM. The experimental results indicate that the hydration products are poorly crystalline C- S- H （ B ）, tobermorite and hydrogarnet. No componeat of clay was found. Unreacted SiO2 cart be in existence, and the structure system of aerated concrete is homogencous and dense.

Impregnation of Crushed Stone with Bitumenous Compounds Using Propane/Butane Impregnation Process Carried out in Supercritical Fluid Conditions

An efficient technology of impregnation of carbonate crushed stone by oil-product based on SCF-impregnation process usage with propane/butane solvent was developed. Regular impregnation throughout the volume of crushed stone sample is achieved. As a result of the appliance of proposed technology, the humidity of the treated crushed stone samples decreased down to 0.54%.

Numerical Analysis of the Settlement of Composite Foundation Reinforced with Crushed Stone Grouting Pile and Rigid Bearing Plate

This paper deals with a new type of crushed stone grouting pile with a rigid bearing plate. The load transfer characteristics were analyzed, and a settlement model of the composite foundation reinforced with crushed stone grouting pile and rigid bearing plate was built by FEM program. The effects of replacement ratio of capping plate, replacement ratio of pile, replacement ratio of grout diffusion zone, pile-soil modulus ratio, and serous-soil modulus ratio, on the composite foundation settlement were discussed. It is concluded that the proposed crushed stone grouting pile with a rigid bearing plate is effective in decreasing the settlement of composite foundation.

Study on the Elasticity-Plasticity-Stickiness of the Railway Crushed Stone Ballast

This paper is mainly aimed at the mechanics characteristic elas of ticity-plasticitystickiness existed in the CWR (continuously welded rails) track plane of the railway crushed stone ballast. As an important mechanics parameter of the CWR track plane, the ballast resistance is mainly influenced by this mechanics characteristic. Through the systematic experimental research and the theoretical analysis, this mechanics characteristic of the ballast resistance is revealed and a reasonable theoretical model is built for it. This study set a sound foundation for further studying the CWR track deformation property. It will be beneficial to the development of high-speed railway in China.

Theoretical Calculation of ITZ Volume Fraction and Morphological Characterization of Crushed Stone in Concrete

According to the morphological characteristics of crushed stone,the sphericity was introduced to establish the theoretical calculation model of volume fraction of interfacial transition zone(ITZ)around crushed stone.The sphericity of crushed stone was obtained by image processing technology and numerical statistics.The experimental results show that when the maximum particle size of coarse aggregate is less than 31.5 mm,the practical sphericity is generally around 0.75,while the sphericity of sand is generally above 0.85.And the closer to 1 the practical sphericity is,the smaller the ITZ volume fraction(V_(ITZ))is,that is,the closer to spherical shape the aggregate is,the lower the ITZ content in concrete is.The V_(ITZ) and ITZ thickness in concrete and mortar have a linear relationship,and the ITZ content in concrete is lower than that in mortar at the same aggregate volume fraction.

Thermal features of Qinghai-Tibet Railway Embankment with Crushed-stone Slope Protection in Permafrost Regions

The Embankment with Crushed-Stone Slope Protection(ECSSP) in permafrost regions is an effective measure to cool subgrade and protect permafrost.It can mitigate the engineering hazards of the Qinghai-Tibet railway in the permafrost regions. Considering the influence of the noctumal cold air during summer months in Qinghai-Tibet Plateau。

降雨强度对含碎石坡耕地侵蚀泥沙有机碳组分流失特征的影响

[目的]明确含碎石坡耕地有机碳组分在不同雨强和碎石含量下的流失特征,进而为坡耕地有机碳流失的防治提供科学支撑。[方法]以含碎石坡耕地黄棕壤为研究对象,在4种碎石含量(0,10%,20%和30%)下以不同降雨强度(60,90,120 mm/h)进行了人工模拟降雨试验。[结果](1)在侵蚀泥沙中细砂粒含量最高(>50%),中活性有机碳含量最高,在碎石含量为20%时,有机碳流失量最多,且以中活性有机碳流失为主;(2)雨强和各有机碳流失含量呈极显著负相关(p<0.01),碎石含量和非活性有机碳流失含量呈显著正相关(p<0.05);(3)雨强主要通过影响粗砂粒、细砂粒来正向影响活性较高有机碳流失,而碎石含量主要通过影响黏粒来正向影响活性低的有机碳流失,雨强(60.2%)对于侵蚀泥沙和有机碳的流失影响程度大于碎石含量(39.8%)。[结论]雨强和碎石的增加都会加快各有机碳的流失速率和流失量,建议坡耕地进行去碎石化处理并将碎石含量保持在10%以下。

New testing methodology for the quantification of rock crushability:Compressive crushing value(CCV)

Crushing is a size reduction process that plays a key role in both mineral processing and crushing–screening plant design. Investigations on rock crushability have become an important issue in mining operations and the manufacture of industrial crusher equipment. The main objective of this research is to quantify the crushability of hard rocks based on their mineralogical and mechanical properties. For this purpose, the mineralogical, physical, and mechanical properties of various hard rocks were determined. A new compressive crushing value(CCV) testing methodology was proposed. The results obtained from CCV tests were compared with those from mineralogical inspections, rock strength as well as mechanical aggregate tests. Strong correlations were found between CCV and several rock and aggregate properties such as uniaxial compressive strength(UCS), the brittleness index(S_(20)), and aggregate impact value(AIV). Furthermore, the relationship between the mineralogical properties of the rocks and their CCVs were established. It is concluded that the proposed testing methodology is simple and highly repeatable and could be utilized as a pre-design tool in the design stage of the crushing process for rock quarries.

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。

盐冻循环作用下水泥稳定碎石混合料的宏细观性能

为研究盐分和冻融循环耦合侵蚀作用下水泥稳定碎石混合料的力学性能、疲劳特性及微细观空隙结构衰减规律,在冻融条件下对不同初始含盐量的水泥稳定碎石混合料开展无侧限抗压强度试验、弯拉强度试验、动态压缩模量试验和三分点加载疲劳试验。基于工业CT无损检测技术研究了盐冻耦合作用下水泥稳定碎石混合料微细观空隙结构衰减规律;提出了盐冻循环次数与盐溶液浓度对水泥稳定碎石混合料力学性能、疲劳性能和微细观空隙直径期望值的衰减公式;建立了微细观空隙结构与宏观力学性能、疲劳性能之间的拟合关系。结果表明:盐冻耦合侵蚀作用加速了水泥稳定碎石混合料力学性能与疲劳特性衰减,随着盐冻循环次数增加,水泥稳定碎石混合料的无侧限抗压强度与动态回弹模量呈指数模型衰减,弯拉强度与疲劳寿命呈三次函数模型衰减;盐冻损伤主要集中在集料边缘的原生空隙部位,微细观等效空隙直径期望值和空隙级配中小于0.1 mm3的空隙数量随着盐冻耦合侵蚀作用次数增加而增大;硫酸钠盐溶液浓度越大,经历相同盐冻循环后水泥稳定碎石混合料力学性能和疲劳性能损伤度越高,微细观等效空隙直径期望值随着硫酸钠盐溶液浓度增大呈线性关系增大;随着等效空隙直径期望值增大,水泥稳定碎石混合料的动态回弹模量、无侧限抗压强度和弯拉强度均呈线性关系减小,同时疲劳寿命呈指数函数关系降低;盐冻耦合侵蚀作用改变了水泥稳定碎石内部微细观空隙结构,是盐冻耦合侵蚀作用导致水泥稳定碎石混合料力学性能和疲劳性能下降的原因之一。

含漂砂卵砾石深厚覆盖层复合地基处理施工关键技术的研究与应用

以硬梁包水电站为依托,针对深厚覆盖层地质条件复杂多变且含巨漂砂卵砾石地层条件,阐述了通过对防渗墙及地下连续墙采用精准施工技术、发泡泥浆护壁工艺、超常规振冲碎石桩填料自动化精确测量、反滤层精准布设施工工艺、振冲桩承载力快速简便检测方法、超深防渗墙防渗单元质量智能融合与辨识关键技术、智能化精确计量超常规振冲碎石桩填料等基础加固和防渗处理方法开展的研究与应用,有效地解决了泥浆漏失和护壁稳定性问题以及超常规碎石桩施工中遇到的技术难题,实现了对超深防渗墙质量的分析和定量评价,降低了防渗体出现隐患的风险,可对差异沉降进行有效管控,对项目施工进度和质量起到了促进作用,所取得的经验可供类似工程参考。

大粒径级配碎石在旋转轴压下永久变形规律

为研究大粒径级配碎石在重复荷载作用下的永久变形规律,在道路材料旋转振动压实仪的基础上提出大粒径级配碎石混合料振动旋转压实室内研究制样方式,并采用旋转轴压重复荷载施加方式对成型试样施加重复荷载,最后引入AASHTO和Monismith模型对变形数据进行拟合。结果表明:当重复旋转轴压荷载等级低于200 kPa时,试样变形最终将趋于稳定,当荷载等级在240~320 kPa时,变形将缓慢累积且增速渐趋变缓,当荷载等级≥360 kPa时,变形将快速累积且增速保持在较高水平;AASHTO模型对低等级重复荷载作用下的累积变形拟合效果更好,Monismith模型对高等级重复荷载作用下的累积变形拟合效果更佳;旋转轴压荷载值、试样含水率和模型拟合参数的变化具有一定的关联。

基于无人机倾斜摄影测量技术的碎石方量计算

针对传统计算碎石方量效率低、成本高的弊端,将无人机倾斜摄影测量技术应用于碎石方量计算中。文中详细叙述该技术应用于碎石方量计算的流程,并以某工程碎石方量计算为实例,与传统碎石方量计算方法进行比较,最终验证了无人机倾斜摄影测量技术应用于碎石方量计算的适用性与可行性。

赤泥基胶凝材料稳定碎石抗裂性能及评价方法

路面半刚性基层具有强度高、稳定性好等优点,但在强度形成及后期服役过程中由于内部相对湿度和温度变化会产生收缩应力,当收缩应力超过胶凝材料自身胶结力时,基层会发生干燥收缩裂缝和温度收缩裂缝.作为一种新型路面基层材料,赤泥基胶凝材料可100%代替水泥用于道路基层建设,然而赤泥基胶凝材料稳定碎石抗裂性能的经时演化规律尚不明确.因此,本文以赤泥基胶凝材料稳定碎石干燥收缩、温度收缩性能为研究对象,探究赤泥基胶凝材料掺量、养生龄期等因素对收缩性能的影响规律并运用灰色关联度确定了干缩抗裂性能指标、温缩抗裂性能指标与最大干缩应变、温缩应变的相关性.试验结果表明赤泥基胶凝材料稳定碎石的干缩应变、温缩应变随胶凝材料掺量的增加先降低后升高且干缩应变、温缩应变增长速率随养生龄期的延长逐渐减小,基于灰色关联度分析法确定了干缩抗裂性指数和温缩系数为赤泥基胶凝材料稳定碎石抗裂性能的最优评级指标,确定了赤泥胶凝材料掺量为7%时,赤泥基胶凝材料稳定碎石抗裂性能最优.

改性小麦秸秆对水泥稳定碎石性能影响研究

为了研究改性小麦秸秆对水泥稳定碎石性能的影响,采用不同浓度的NaOH溶液对小麦秸秆进行了表面改性处理,并分析了NaOH溶液浓度和改性时间对秸秆质量的影响。将改性后的秸秆纤维掺入水泥稳定碎石中,通过无侧限抗压强度试验、劈裂强度试验得到最佳纤维配比,在最佳纤维配比下进行干缩试验、冻融试验,结合环境扫描电子显微镜(ESEM)测试,观察改性前后小麦秸秆微观变化及秸秆纤维在水泥稳定碎石内的作用机理。研究结果表明:采用质量分数为3.5%的NaOH溶液对小麦秸秆进行12 h的改性处理时,小麦秸秆的质量损失率较高,可减轻对水泥的缓凝作用;秸秆纤维对水泥稳定碎石的力学性能具有显著增强作用,纤维长度为20 mm、掺量为0.15%(质量分数)时强度最高,且随着养护龄期的延长,水泥稳定碎石力学性能不断提升。秸秆纤维水泥稳定碎石与普通水泥稳定碎石相比,其干缩性能和抗冻性能均有明显改善;ESEM分析表明改性后的小麦秸秆可以提升其与基体的黏结,阻止或延缓水泥裂缝的产生和发展,提高水泥稳定碎石的力学性能和抗裂性能。

煤矸石集料混凝土的工作性能和力学性能研究

文中通过试验和理论分析,探讨了煤矸石集料混凝土的基本工作性能和力学性能以及其对环境的影响。结果表明,煤矸石作为集料应用在混凝土中,虽然会使混凝土的工作性能以及强度降低,但通过合理的配比,其性能依然能满足规范要求,说明煤矸石作为集料掺入混凝土存在可行性,后期可充分发挥其特点,制备轻质高强或吸附性的特殊混凝土。

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。

公路预防性养护技术在现代公路中的应用

通过预防性养护能够显著提高公路通行质量,延长公路使用寿命。本文以此为研究目标,在总结公路预防性养护指导指数基础上,分别对碎石封层技术以及稀浆封层技术的具体应用与效果进行阐述。研究发现上述两种方式均能够达成预防性养护目标。相较而言,基于新材料的稀浆封层技术施工便捷、迅速,具有更大的推广价值。

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。

无砟轨道泡沫混凝土路基碎石夹层结构动力特性试验研究

为研究无砟轨道泡沫混凝土路基碎石夹层结构的动力特性和长期动力稳定性,建立夹层结构足尺试验模型,开展变频加载和循环加载试验。研究结果表明,在变频动载作用下,夹层结构的振动加速度、动位移和动土压力呈增大规律但无峰值出现,表明夹层结构未产生共振现象;为降低加载频率对比值系数的影响,建议采用底座板与路基面之间振动位移比值系数作为基床或级配碎石夹层对无砟轨道结构支承状态分析的判据。循环动载作用下,夹层结构的振动加速度、动位移和动土压力在加载至100万次后趋于稳定;相较传统土石填料路基,泡沫混凝土层能更好地均化上部荷载;经200万次动载作用后,试验模型总累积沉降为0.898 mm,碎石夹层的压缩变形占总累积沉降的82.9%。试验结果表明,在无砟轨道结构与泡沫混凝土层之间设置厚度为0.7 m的级配碎石夹层,可为线路提供平顺性和稳定性。