垂直振动压实SRX稳定碎石力学性能影响因素研究

为了揭示有机聚合物SRX稳定碎石(SRX-SCS)强度形成机理及影响因素,通过室内垂直振动成型试件,研究相对含水率、SRX含量、压实度与集料岩性对SRX-SCS力学性能的影响,并建立了各强度之间的关系.结果表明:SRX-SCS抗压强度、劈裂强度和回弹模量均随着相对含水率的减小而增大,且相对含水率为0时,三者均达到最大值;力学强度随着SRX含量的增加而增大;压实度在96%~100%之间,压实度每提高1%,SRX-SCS抗压强度提高4%~8%,劈裂强度提高6%~10%,回弹模量提高7%~11%;SRX石灰岩稳定碎石的抗压强度是SRX砂岩稳定碎石、SRX花岗岩稳定碎石的1.27倍、2.19倍,劈裂强度是砂岩、花岗岩的1.23倍、2.03倍,回弹模量是砂岩、花岗岩的1.21倍、2.20倍;抗压强度Rc与劈裂强度Ri之间满足Rc=16.6Ri,抗压强度Rc与回弹模量Ec之间满足Ec=118.4Rc.该成果可为SRX-SCS的路面结构与材料设计提供理论基础.     

Hybrid effect,mechanical properties and enhancement mechanism of oil-well cement stone with multiscale silicon carbide whisker

Cement-based materials typically have a relatively high compressive strength and a relatively low tensile strength. In this paper, multiscale silicon carbide whiskers (SW) were used to improve mechanical properties of oil-well cement stone. The structure and properties of whisker cement stone were analyzed via mechanical testing and cement sheath integrity. The results demonstrated that multiscale SW mixing showed a positive hybrid effect and could effectively improve the compressive strength, the flexural strength, and the splitting tensile strength of oil-well cement stone by 8.96%, 137.44% and 27.96%. The modulus and porosity of the whisker cement stone significantly reduced. The filling effect, whisker pinning, the pullout, and the whisker bridging were regarded as effective mechanisms for the addition of SW when improving the mechanical properties and microstructures of oil-well cement stone.     

石粉含量对C45凝灰岩机制砂混凝土性能的影响

采用坍落度、振动凯氏球体试验,以及抗压强度、静压弹性模量、劈裂抗拉、混凝土表观电阻率试验,分析了石粉含量对C45凝灰岩机制砂混凝土(MSC)工作性、力学性能、抗氯离子渗透性能的影响;通过二次项式拟合分析,结合MSC与天然砂混凝土(NSC)的对比研究,给出了C45凝灰岩MSC的推荐石粉含量。结果表明:随着石粉含量的提高,C45凝灰岩MSC的坍落度、振动凯氏系数、抗压强度、静压弹性模量、劈裂抗拉强度、抗氯离子渗透性能均先增大后减小,存在最佳石粉含量;当对混凝土的要求为坍落度>100 mm、静压弹性模量>44 GPa时,C45凝灰岩MSC的推荐石粉含量为2%~5%(质量分数,下同);当对混凝土的要求为坍落度<100 mm、静压弹性模量<44 GPa时,推荐石粉含量为可放宽为5%~8%;合理控制机制砂石粉含量可以使C45凝灰岩MSC的综合性能优于C45 NSC。     

湿陷性黄土地区劈裂注浆桩芯结石体强度试验研究

为研究湿陷性黄土地区劈裂注浆桩芯结石体力学性能,通过配置五种不同配合比的注浆浆液,对其标准养护试块、同条件养护试块以及桩芯结石体分别进行龄期为3 d、7 d、14 d、28 d、56 d、90 d的抗压强度测试。结果表明:桩芯结石体的抗压强度随水胶比的增大而降低,随养护龄期的增加而呈对数增大;注浆浆液的析水率对桩芯结石体的抗压强度影响较大,黄土的密度、含水率以及桩芯结石体在黄土中的埋置深度对其抗压强度影响较小。通过影响因素分析,推出桩芯结石体抗压强度与同浆液3 d标准养护试块抗压强度的相关关系,此关系式可对湿陷性黄土地区地基加固工程的效果进行预估,为湿陷性黄土地区地基加固工程提供了桩芯结石体抗压强度的参考。     

海泡石纤维增强高石粉含量机制砂砂浆性能的研究

以高石粉含量机制砂砂浆为研究对象,分析了海泡石纤维体积掺量和长度的变化对砂浆力学性能和干燥收缩的影响规律,并使用压汞仪和扫描电子显微镜研究了砂浆内部孔结构和微观形貌的变化特征。结果表明:适宜体积掺量的短海泡石纤维可显著改善砂浆的抗压强度、抗折强度和抗干燥收缩能力。与空白组相比,长度为1 mm的纤维体积掺量为1.5%时,试件28 d抗压强度和抗折强度分别提高98.9%和36.2%;长度为1 mm的纤维体积掺量为2.0%时,28 d自然干燥收缩值降低72.1%。海泡石纤维试件内部形成了大量针棒状钙矾石和片状氢氧化钙晶体,有效提高了砂浆硬化体系的密实性,砂浆总孔隙率与纤维掺量成反比。     

The correlation of agglomerate strength with size

The compressive strength of dried sand spheres held together by NaCl crystal bridges was investigated. Agglomerate diameter, sand particle size, drying temperature and salt concentration were varied. Compressive strength L was correlated with pellet diameter D by the equation: L=kDⁿ The values obtained forthe parameters k and n were interpreted in terms of the mode of crystallization of the salt and the distribution of the salt bridges. A simple model is presented to explain the variation of the exponent n with the uniformity of binding in agglomerates.     

Salt Crystal Growth as Weathering Mechanism of Porous Stone on Historic Masonry

It is well known that in porous stones, NaCl precipitation on and beneath a surface depends on the solution supply and the evaporation rate according to the microclimate and the effective pore structure.In the present work, the study of salt crystal growth mechanisms in large heterogeneous systems like porous stone masonries is attempted. The historic masonries of the Medieval City of Rhodes act as a pilot, due to the intense marine environment and the climatic conditions in favour of NaCl crystallization into the highly porous stones.Weathered monument samples from various depths on masonries exposed to the sea are examined systematically under SEM and EPMA. The obtained results permit the differentiation of crystal growth patterns occurring during distinguished phases of the evaporation process within the porous stone masonry in depth.In the first phase, salt crystals grow favourably in the larger pores, connecting with the empty evaporation channels, and being supplied by solution from the next smaller pores. The isometric crystal habits attaining an equilibrium form correspond to those growing immersed in the solution, when a granular crust is formed.In a second phase, the crystals already exceed the pore size and overlap other smaller pores. As the rate of evaporation exceeds the solution supply, the solution retires and the substrate dries out, the area where the crystal contacts the solution is reduced, and consequently, columnar crystals grow.The pressure exerted by crystallization against the pore walls, when the crystals filling entirely the coarse pores continue growing, leads to disruption.     

盐水与冻融耦合作用对玄武岩纤维水泥土性能影响研究

冻融循环作用与外界环境的侵蚀是影响水泥土强度的主要因素,探索如何提高水泥土在寒冷地区盐水侵蚀环境下的强度及其发展规律是一个重要的课题。通过盐冻试验和无侧限抗压强度试验,研究了玄武岩纤维水泥土在不同溶液(3.5%(质量分数,下同)NaCl溶液、3.5%Na₂SO₄溶液、3.5%(NaCl+Na₂SO₄)混合溶液、清水)与冻融循环作用耦合下的力学性质与表观特征,探讨了养护温度、侵蚀溶液类型、冻融循环次数等变量对水泥土性能的影响。在此基础上,采用Logistic生长模型,对不同环境下水泥土试块的强度进行回归分析。研究结果表明:低温养护环境会抑制水泥土强度的发展;随着冻融次数的增加,试块出现了不同程度的质量损失、表面破坏,以及无侧限抗压强度降低的现象;在相同冻融次数下,玄武岩纤维水泥土的破坏程度由强到弱依次为硫酸盐冻＞混合盐冻＞氯盐冻＞水冻;而掺入玄武岩纤维可使水泥土经历更多次的冻融循环,有效降低强度损失率,提高水泥土的抗冻性;通过回归分析,得到不同试验组的强度衰减模型和预期强度。     

偏高岭土对模拟商混站强碱性废泥基人造石强度的影响

为实现商混站强碱性废泥的资源化利用,以实验室模拟的商混站强碱性废泥为对象进行人造石制备研究,探究了偏高岭土掺量及水灰比对人造石强度的影响规律及机理,并借助XRD和SEM分析了人造石的物相组成及微观形貌。结果表明:添加偏高岭土可以显著提高人造石的固结强度,当偏高岭土掺量为6%(质量分数)时抗压强度增幅最大,相对于对照组,14 d、28 d强度增长率分别为18.2%、20.3%;随着水灰比的增加,人造石抗压强度呈先增大后减小的趋势,14 d、28 d的抗压强度分别在水灰比为0.44、0.46时达到最大,分别为44 MPa、46 MPa。     

砂岩石质文物灌浆材料的成分设计及多场景应用研究

为了制备出性能可调且满足多场景应用的砂岩石质文物灌浆材料,采用四角配料法,以水硬性石灰(NHL2)、硫铝酸盐水泥(SAC)、偏高岭土(MK)和水性环氧树脂(WER)为原料,制备出不同配方的灌浆材料,并对其力学性能、凝结时间、流动性、粘接强度等进行测试分析。结果表明,NHL2和MK含量较高的灌浆材料,抗压强度和粘接强度较低,适用于修复壁画或镶嵌图案。SAC和WER含量较高的灌浆材料,抗压强度和粘接强度较高,适用于修复断崖、悬岩型砂岩石质文物。WER和MK含量较高的灌浆材料,韧性和变形能力良好,适用于修复易受外界应力的砂岩石质文物。     

Mechanical response and crack propagation of oil well cement under dynamic and static loads

The dynamic mechanical properties and fracture mechanism of three types of oil well cement with different formulations were investigated using a Φ50?mm split Hopkinson pressure bar (SHPB) and quasi-static mechanical tests were conducted with a hydraulic universal testing machine. The stress-strain diagram, time-stress diagram, total energy absorption diagram, and the dynamic growth factor (DIF) under different strain rates were obtained. The crack propagation process of the oil well cement under dynamic loading is evaluated using high-speed photography to determine the fracture mechanism. The test results show that the strength of the cement increases under a dynamic impact. The compressive strength of the pure cement increases from 37?MPa to 184.80?MPa under static loading. However, the peak stress of the cement stone strengthened with cellulose fiber is lower under a dynamic load than a static load. Under dynamic loading, the absorption energy is higher for the pure cement stone than for the cement stone reinforced with whiskers and cellulose. Furthermore, the crack initiation, crack propagation, and fracture characteristics of the oil well cement are different under dynamic and static loads. Under a static load, the rupture of the cement is the result of the propagation of the tensile cracks. Under dynamic loading, there are fewer micro cracks on the cement surface and a composite fracture results from tensile and shear cracks.     

高强度脱硫石膏复合材料制备与力学性能

研究了材料参数和工艺参数对β型半水脱硫石膏-水泥复合材料力学性能及结构特征的影响。结果表明,β型半水脱硫石膏-水泥复合材料的28d抗折、抗压强度分别是9.38MPa和48.84MPa;掺磨细矿物β型半水脱硫石膏-水泥复合材料的28d抗折、抗压强度分别为10.88MPa和67.67MPa;其软化系数分别为0.93和0.81。结构分析表明,掺磨细矿物β型半水脱硫石膏-水泥复合材料水化产物中,除二水硫酸钙外,还出现C-S-H凝胶和AFt晶体,这些胶体与晶体互相交织,降低孔隙率,提高了密实性和强度。     

瓷石的工艺矿物学特征与选矿研究

论述了瓷石的工艺矿物学持证，研究了瓷石的选矿工艺，并对江西宁村和上祝瓷石进行选矿实验取得了满意结果。     

The microstructural and mechanical properties of geopolymer composites containing glass microfibres

This paper presents the effects of microfibre contents on mechanical properties of fly ash-based geopolymer matrices containing glass microfibres at 0, 1, 2 and 3 mass%. The influence of glass microfibres on the fracture toughness, compressive strength, Young's modulus and hardness of geopolymer composites are reported, as are the microstructural properties investigated using scanning electron microscopy. Results show that the addition of 2 mass% glass microfibres was optimal, exhibiting the highest levels of fracture toughness, compressive strength, Young's modulus and hardness. The results of the microstructural analysis indicate that the glass microfibres act as a filler for voids within the matrix, making a dense geopolymer and improving the microstructure of the binder. This leads to favourable adhesion of the composites, and produces a geopolymer composite with good mechanical properties, comparable to pure geopolymer. The failure mechanisms in glass microfibre-reinforced geopolymer composites are discussed in terms of microstructure.     

页岩配料在立筒预热器窖上的应用及其改进

用页岩替代粘土配料可生产出早强型的硅酸盐水泥熟料。用其配制矿渣水泥,凝结时间快,早、后期强度均高。用页岩－砂岩配料,可改变页岩单独配料熟料２８ｄ抗压强度低的问题。对燃烧工艺方面的改进,可使页岩配料引起的窑尾系统结堵问题得到缓解。     

废弃石粉对低密度聚乙烯非等温结晶过程以及拉伸性能的影响

将废弃石材加工过程中的副产物石粉引入到低密度聚乙烯(LDPE)中,实现对废弃石粉的回收利用。采用了差示扫描量热法(DSC)、广角X射线衍射(XRD)以及电子万能试验机研究了LDPE/石粉复合材料的结晶动力学、结晶形态以及力学性能。结果表明:石粉对于LDPE的结晶过程影响有限,复合材料与聚合物的结晶峰顶温度以及半峰宽相差无几;复合材料的结晶结构与结晶形态与聚合物相比无明显变化;在石粉含量为20%(质量分数)时,复合材料的拉伸屈服强度仍然保持了与聚合物几乎相同的数值。研究结果显示,石粉作为一种惰性填料,完全能够用于LDPE的填充改性。     

Opal-A rich additives used in ancient lime mortars

Ancient stone and brick masonry mortars from three monuments in Konya, Central Anatolia dated to the Anatolian Selçuk Period (12th and 13th centuries AD) were examined for their raw material composition and durability characteristics to understand some characteristics of medieval mortar technology.Optical microscopy, XRD, SEM, EDX, FTIR and TGA analyses revealed that the mortars contained high percentage of lime binder totally carbonated into micritic calcite. Coarse and medium aggregates were mainly composed of sandstone and metamorphic rock fragments, quartz, feldspar and mica minerals. Opal-A was found in considerable amounts in the fine aggregates, likely not derived from the coarser ones but added separately. Pozzolanic activity of the fine aggregates was determined by conductometric measurements. Their ability to form C-S-H was observed by treating them with saturated Ca(OH)₂ solution.Bulk density and total porosity measurements showed that the mortars were highly porous due to the use of high amount of lime. On the other hand, they possessed sufficient mechanical strength. Mechanical properties were determined by point load tests and ultrasonic pulse velocity measurements. They were expressed as uniaxial compressive strength (UCS) and modulus of elasticity (E_mod) in MPa.The results were also discussed in terms of durability characteristics of the mortars. They were expressed with the use of uniaxial compressive strengths in dry and wet states, and total porosity values. The mortars were considered to have high durability to wetting and drying cycles but had poor durability to the crystallization of water-soluble salts.     

Melt Mastication of Isotactic Polyproyplene for Improved Thermal and Physical Properties

Herein a new polymer processing method referred to as Melt-Mastication (MM) is presented as way to substantially improve the thermal and mechanical properties of Polypropylene (iPP) and other semi-crystalline polymers. MM is a low temperature mixing technique that subjects molten iPP to chaotic flow under at temperatures between the melting and crystallization temperatures, thereby promoting flow induced crystallization (FIC). The resulting materials demonstrate an unusual crystal morphology that is highly crystalline by thermal calorimetry (57% crystal volume fraction), melts at a temperature 10.3 K higher than conventionally processed iPP, and demonstrates melt memory after annealing at 200°C. The highly crystalline morphology does not show birefringence in polarized optical microscopy and by SEM and AFM appears to be comprised of largely disorganized lamellar crystals, with possible stacked ordering in local (~1 μm) regions. Melt-Masticated iPP demonstrates improved compressive modulus (+77%), strength (+40%), and strain hardening modulus in uniaxial compression, which are attributed to enhanced crystal volume fraction, lamellar crystal thickness, and network connectivity, respectively. POLYM. ENG. SCI., 60: 380–386, 2019. © 2019 Society of Plastics Engineers     

聚乙烯醇纤维水泥稳定碎石的疲劳性能研究

为研究掺聚乙烯醇纤维水泥稳定碎石的疲劳性能,首先根据聚乙烯醇纤维对水泥稳定碎石力学性能的影响规律,确定纤维最佳掺量和长度。基于间接拉伸疲劳试验和Weibull分布,对其疲劳寿命测试结果进行分析并建立疲劳方程。结果表明,聚乙烯醇纤维最佳掺量和长度为0.06%(质量分数)和24 mm;在最佳掺量和长度下,与未掺加纤维的水泥稳定碎石材料相比,聚乙烯醇纤维水泥稳定碎石的无侧限抗压强度提高约24%,劈裂强度提高约26%;对比不掺纤维的水稳碎石材料,其疲劳寿命也呈显著优势,当水泥用量为4%(质量分数)时,掺聚乙烯醇纤维与不掺纤维水泥稳定碎石斜率b之比为0.94~0.99,截距a之比为1.06~1.23。     

Influence of NaCl on Granulometric Characteristics and Polymorphism in Batch‐Cooling Crystallization of Glycine

The effect of NaCl added in different quantities on thermodynamic properties, granulometric characteristics, and structure of glycine in a crystallization process was investigated. Solubilities of α‐ and γ‐polymorphs in the presence of varying amounts of NaCl were analyzed. In order to examine the impact of the additive on granulometric properties of glycine, crystal morphology was examined by observing crystals under a scanning electron microscope. Crystal size distribution was determined by sieve analysis. By X‐ray diffraction analysis, the critical concentration of NaCl at which the structure of glycine changed, could be defined. The purity of obtained polymorphs was confirmed by Fourier transform infrared spectroscopy.