Flexural and shear bond characteristics of thin layer polymer cement mortared concrete masonry

This paper presents an experimental investigation of the flexural and shear bond characteristics of thin layer polymer cement mortared concrete masonry. It is well known that the bond characteristics of masonry depend upon the mortar type, the techniques of dispersion of mortar and the surface texture of concrete blocks; there exists an abundance of literature on the conventional 10 mm thick cement mortared masonry bond; however, 1-4 mm thick polymer cement mortared masonry bond is not yet well researched. This paper reports a study on the examination of the effect of mortar compositions, dispersion methods and unit surface textures to the flexural and shear bond characteristics of thin layer mortared concrete masonry. A non-contact digital image correlation method was adopted for the measurement of strains at the unit-mortar interface in this research. All mortar joints have been carefully prepared to ensure achievement of the desired thin layer mortar thickness on average. The results exhibit that the bond strength of thin mortar layered concrete masonry with polymer cement mortar is higher than that of the conventional masonry; moreover the unit surface texture and the mortar dispersion methods are found to have significant influence on the flexural and shear bond characteristics. From the experimental results, a correlation between the flexural and the shear bond strengths has been determined and is presented in this paper.

Age and curing effect on the bond strength of thin bed concrete masonry with polymer cement mortar

Bond characteristics of masonry are partly affected by the type of mortar used, the techniques of dispersion of mortar and the surface texture of the concrete blocks. Additionally it is understood from the studies on conventional masonry, the bond characteristics are influenced by masonry age and curing methods as well as dryness/dampness at the time of testing. However, all these effects on bond for thin bed masonry containing polymer cement mortar are not well researched. Therefore, the effect of ageing and curing method on bond strength of masonry made with polymer cement mortar was experimentally investigated as part of an ongoing bond strength research program on thin bed concrete masonry at Queensland University of technology. This paper presents the experimental investigation of the flexural and shears bond characteristics of thin bed concrete masonry of varying age/ curing methods. Since, the polymer cement mortar is commonly used in thin bed masonry; bond development through two different curing conditions (dry/wet) was investigated in this research work. The results exhibit that the bond strength increases with the age under the wet and dry curing conditions; dry curing produce stronger bond and is considered as an advantage towards making this form of thin bed masonry better sustainable.

Characterisation of thin layer polymer cement mortared concrete masonry bond

Masonry bond is affected by many parameters such as the type of mortar used, the techniques of dispersion of mortar and the surface texture of the concrete blocks. Additionally it is understood from the studies on conventional masonry that the bond characteristics are also influenced by the curing methods as well as the age of the bond at the time of testing. These effects on thin layer mortared masonry employing polymer cement mortars are not well understood. Therefore, the effect of curing methods and age to the bond strength and deformation of masonry containing thin layered polymer cement mortar was investigated as part of an ongoing research program at the Queensland University of Technology. This paper presents an experimental investigation of the flexural and shear bond characteristics of the thin layer mortared concrete masonry. The parameters examined include the effects curing and ageing to the bond development over a period from 14 days to 56 days after fabrication. The results exhibit that dry cured thin layer mortared masonry exhibits higher bond strength and Young’s and shear moduli compared to the wet cured specimens.

Effect Of Directionality Of Grinding Marks On Friction And Formation Of Transfer Layer

Surface texture influences friction and transfer layer formation during sliding. In the present investigation, basic studies were conducted using inclined pin-on-plate sliding tester to understand the effect of directionality of surface grinding marks of hard material on friction and transfer layer formation during sliding against soft materials. 080 M40 steel plates were ground to attain different surface roughness with unidirectional grinding marks. Then pins made of soft materials such as pure Al, pure Mg and Al-Mg alloy were slid against the prepared steel plates. Grinding angle (i.e., the angle between direction of sliding and grinding marks) was varied between 0 degrees and 90 degrees in the tests. Experiments were conducted under both dry and lubricated conditions on each plate in ambient environment. It was observed that the transfer layer formation and the coefficient of friction, which has two components adhesion and plowing - depend primarily on the directionality of grinding marks of the harder mating surface, and independent of surface roughness of the harder mating surface. For the case of pure Mg, stick-slip phenomenon was observed under dry condition for all grinding angles and it was absent upto 20 degrees grinding angles under lubricated condition. However, for the case of Al, it was observed only under lubricated conditions for angles exceeding 20 degrees. As regards the alloy, namely, Al-Mg alloy, it, was absent in both conditions. For the case of pure Mg and Al, it was observed that the amplitude of stick-slip motion primarily depends on plowing component of friction. The grinding angle effect on coefficient of friction was attributed to the variation of plowing component of friction with grinding angle.

Studies On Friction And Formation Of Transfer Layer In Hcp Metals

Surface texture plays an important role in the frictional behavior and transfer layer formation of contacting surfaces. In the present investigation, basic experiments were conducted using an inclined pin-on-plate sliding apparatus to better understand the role of surface texture on the coefficient of friction and the formation of a transfer layer. In the experiments, soft HCP materials such as pure Mg and pure Zn were used for the pins and a hardened 080 M40 steel was used for the plate. Two surface parameters of the steel plates—roughness and texture—were varied in tests that were conducted at a sliding speed of 2 mm/s in ambient conditions under both dry and lubricated conditions. The morphologies of the worn surfaces of the pins and the formation of the transfer layer on the counter surfaces were observed using a scanning electron microscope. In the experiments, the occurrence of stick-slip motion, the formation of a transfer layer, and the value of friction were recorded. With respect to the friction, both adhesion and plowing components were analyzed. Based on the experimental results, the effect of surface texture on the friction was attributed to differences in the amount of plowing. Both the plowing component of friction and the amplitude of stick-slip motion were determined to increase surface textures that promote plane strain conditions and decrease the textures that favor plane stress conditions.

Effect of water vapour stabilization of raw materials on the quality of the inhalation product

Generation of raw materials for dry powder inhalers by different size reduction methods can be expected to influence physical and chemical properties of the powders. This can cause differences in particle size, size distribution, shape, crystalline properties, surface texture and energy. These physical properties of powders influence the behaviour of particles before and after inhalation. Materials with an amorphous surface have different surface energy compared to materials with crystalline surface. This can affect the adhesion and cohesion of particles. Changes in the surface nature of the drug particles results in a change in product performance. By stabilization of the raw materials the amorphous surfaces are converted into crystalline surfaces. The primary aim of the study was to investigate the influence of the surface properties of the inhalation particles on the quality of the product. The quality of the inhalation product is evaluated by measuring the fine particle dose (FPD). FDP is the total dose of particles with aerodynamic diameters smaller than 5,0 μm. The secondary aim of this study was to achieve the target level of the FPD and the stability of the FPD. This study was also used to evaluate the importance of the stabilization of the inhalation powders. The study included manufacturing and analysing drug substance 200 μg/dose inhalation powder batches using non-stabilized or stabilized raw materials. The inhaler formulation consisted of micronized drug substance, lactose <100μm and micronized lactose <10μm. The inhaler device was Easyhaler®. Stabilization of the raw materials was done in different relative humidity, temperature and time. Surface properties of the raw materials were studied by dynamic vapour sorption, scanning electron microscopy and three-point nitrogen adsorption technique. Particle size was studied by laser diffraction particle size analyzer. Aerodynamic particle size distribution from inhalers was measured by new generation impactor. Stabilization of all three raw materials was successful. A clear difference between nonstabilized and stabilized raw materials was achieved for drug substance and lactose <10μm. However for lactose <100μm the difference wasn’t as clear as wanted. The surface of the non-stabilized drug substance was more irregular and the particles had more roughness on the surface compared to the stabilized drug substances particles surface. The surface of the stabilized drug particles was more regular and smoother than non-stabilized. Even though a good difference between stabilized and non-stabilized raw materials was achieved, a clear evidence of the effect of the surface properties of the inhalation particles on the quality of the product was not observed. Stabilization of the raw materials didn’t lead to a higher FPD. Possible explanations for the unexpected result might be too rough conditions in the stabilization of the drug substance or smaller than wanted difference in the degree of stabilization of the main component of the product <100μm. Despite positive effects on the quality of the product were not seen there appears to be some evidence that stabilized drug substance results in smaller particle size of dry powder inhalers.

Synergetic roles of concrete ingredients in strength development

Concrete is basically a heterogeneous material made up of ingredients with distinct physical and mechanical properties. As a result, the presence of interphases is inevitable. In the processing of concrete, fresh and hardened states are the two distinct stages. In the fresh state, the presence of inert constituents in the cement mortar matrix only dilutes the overall potential of concrete to flow. In the hardened state the synergetics play a dominant role in strength development. When the strength of coarse aggregate is far higher than the strength levels for which the matrix or concrete is processed, interphase bonding plays a dominant role on the strength. When the matrix strength is comparable to that of the aggregate strength, in contrast, the concrete strength is affected by the aggregate strength. Besides these aspects, the effects of the size and the surface texture of coarse aggregates have also been analysed. Copyright (C) 1996 Elsevier Science Ltd.

The Role of Strain Rate Response on Tribological Behavior of Metals

In an effort to study the role of strain rate response on the tribological behavior of metals, room temperature experiments were conducted by sliding commercially pure titanium and a-iron pins against an H-11 die steel flats of various surface textures. The steel flat surface textures were specifically prepared to allow for imposing varying amounts of strain rates at the contacting interface during sliding motion. In the experiments, it was observed that titanium (a harder material than iron) formed a transfer layer on H-11 steel surface textures that produced higher strain rates. In contrast, the titanium pins abraded the steel surfaces that produced lower strain rates. The iron pins were found to abrade the H-11 steel surface regardless of the surface texture characteristics. This unique tribological behavior of titanium is likely due to the fact that titanium undergoes adiabatic shear banding at high strain rates, which creates pathways for lower resistance shear planes. These shear planes lead to fracture and transfer layer formation on the surface of the steel flat, which ultimately promotes a higher strain rate of deformation at the asperity level. Iron does not undergo adiabatic shear banding and thus more naturally abrades the surfaces. Overall, the results clear indicated that a materials strain rate response can be an important factor in controlling the tribological behavior of a plastically deforming material at the asperity level. DOI: 10.1115/1.4007675]

Contaminants removal by bentonite amended slow sand filter

Earlier studies have indicated that variability in size, surface texture and charge greatly influence the contaminant removal process in granular media. Based on surface characteristics of montmorillonite, it is anticipated that small addition of this clay would increase adhesion sites for bacterial growth and extracellular polymer production in the slow sand filter and thereby enhance its contaminant removal ability. Experiments were performed by permeating groundwater contaminated with pathogens (total coliform and E. Coli) and inorganic contaminants through the bentonite amended slow sand filter (BASSF). Surprisingly, the BASSF retained inorganic contaminants besides pathogens. Water-leach tests (pH of water leachate ranged from 2 to 9) with spent BASSF specimen indicated that the inorganic contaminants are irreversibly adsorbed to a large extent. It is considered that the combined effects of enhanced-organic matter mediated adhesion sites and increased hydraulic retention time enables the BASSF specimen to retain inorganic contaminants. It is envisaged that BASSF filters could find use in treating contaminated groundwater for potable needs at household and community level.

Transition from Cassie to impaled state during drop impact on groove-textured solid surfaces

Liquid drops impacted on textured surfaces undergo a transition from the Cassie state characterized by the presence of air pockets inside the roughness valleys below the drop to an impaled state with at least one of the roughness valleys filled with drop liquid. This occurs when the drop impact velocity exceeds a particular value referred to as the critical impact velocity. The present study investigates such a transition process during water drop impact on surfaces textured with unidirectional parallel grooves referred to as groove-textured surfaces. The process of liquid impalement into a groove in the vicinity of drop impact through de-pinning of the three-phase contact line (TPCL) beneath the drop as well as the critical impact velocity were identified experimentally from high speed video recordings of water drop impact on six different groove-textured surfaces made from intrinsically hydrophilic (stainless steel) as well as intrinsically hydrophobic (PDMS and rough aluminum) materials. The surface energy of various 2-D configurations of liquid-vapor interface beneath the drop near the drop impact point was theoretically investigated to identify the locally stable configurations and establish a pathway for the liquid impalement process. A force balance analysis performed on the liquid-vapor interface configuration just prior to TPCL de-pinning provided an expression for the critical drop impact velocity, U-o,U-cr, beyond which the drop state transitions from the Cassie to an impaled state. The theoretical model predicts that Uo, cr increases with the increase in pillar side angle, a, and intrinsic hydrophobicity whereas it decreases with the increase in groove top width, w, of the groove-textured surface. The quantitative predictions of the theoretical model were found to show good agreement with the experimental measurements of U-o,U-cr plotted against the surface texture geometry factor in our model, {tan(alpha/2)/w}(0.5).

Aspects of the washout of salmonid eggs. 1. Observations on the physical characteristics of real and artificial eggs, their rate of fall in a water column and their pattern of settlement in an experimental channel

When salmonid redds are disrupted by spates, the displaced eggs will drift downstream. The mean distance of travel, the types of locations in which the eggs resettle and the depth of reburial of displaced eggs are not known. Investigation of these topics under field conditions presents considerable practical problems, though the use of artificial eggs might help to overcome some of them. Attempts to assess the similarities and/or differences in performance between real and artificial eggs are essential before artificial eggs can validly be used to simulate real eggs. The present report first compares the two types of egg in terms of their measurable physical characteristics (e.g. dimensions and density). The rate at which eggs fall in still water will relate to the rate at which they are likely to resettle in flowing water in the field. As the rate of fall will be influenced by a number of additional factors (e.g. shape and surface texture) which are not easily measured directly, the rates of fall of the two types of egg have been compared directly under controlled conditions. Finally, comparisons of the pattern of settlement of the two types of egg in flowing water in an experimental channel have been made. Although the work was primarily aimed at testing the value of artificial eggs as a simulation of real eggs, several side issues more directly concerned with the properties of real eggs and the likely distance of drift in natural streams have also been explored. This is the first of three reports made on this topic by the author in 1984.

Fabrication, densification, and replica molding of 3D carbon nanotube microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, labon- a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1,2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3. © 2012 Journal of Visualized Experiments.

Effective recombination velocity of textured surfaces

Surface texturization is an effective way to enhance the absorption of light for optoelectronic devices but it also aggravates the surface recombination by enlarging the surface area. In order to evaluate the influence of texture structures on the surface recombination, an effective surface recombination velocity is defined which is assumed to have an equivalent recombination effect on a flat surface. Based on numerical and analytical calculation, the dependences of effective surface recombination on the pattern geometry, the surface recombination velocity, and the diffusion length are analyzed.

Fabrication, characterization and conductivity of organic-inorganic hybrid Langmuir-Blodgett films based on polyquinoline and rare earth-substituted heteropolymolybdate

The organic/inorganic hybrid Langmuir-Blodgett (LB) films were obtained by the compact organization of poly(1,2-dihydro-2,2,4-trimethyl)quinoline (PQ), octadecylamine (ODA) and rare earth-substituted heteropolymolybdates. They were characterized by surface pressure-area (pi-A) isotherms, absorption spectra, fluorescence spectra, atomic force microscope (AFM) and scanning tunneling microscopy (STM). The atomic force microscope revealed a granular surface texture of nanosized rare earth-substituted heteropolymolybdate. The scanning tunneling microscopy indicated that the hybrid LB films containing rare earth-substituted heteropolymolybdates had the better electrical conductivity than LB film of PQ/ODA.

贵州碳酸盐岩风化壳次生石英表面结构、裂变径迹测年及其指示意义

我国西南地区分布有广阔的亚热带潮湿区岩溶，以贵州为中心，总面积达50万km2，是世界上连片分布面积最大的岩溶区。贵州高原地处青藏高原东南缘,云贵高原的东翼，是中国大陆“西高东低”地貌格局中重要的过渡区段，对其新生代地质、地貌演化进行研究无疑具有重要的意义，不仅是对贵州薄弱的新生代地质、地貌研究的补充，而且可以直接通过夷平面展开与青藏高原的对比，探讨青藏高原隆升对贵州高原的直接影响。风化壳作为夷平面的组成部分，在过去没有引起足够的重视，但随着成功实例的不断出现，人们逐渐开始认识到风化壳是夷平面识别和重建的重要依据，也是夷平面环境信息的重要载体。贵州作为碳酸盐岩集中分布区，碳酸盐岩风化壳剖面广泛存在，尤其在黔中、黔北等地区各级夷平面上均发育有红色风化壳，利用碳酸盐岩红色风化壳能为夷平面的识别和形成时代的确立提供可靠的证据，特别是风化壳形成年龄的确定对夷平面时标的建立更具有积极意义。有关贵州地区红色风化壳形成时代的确定，多年来已有一些学者对此展开了研究，但贵州红色风化壳形成时代的确定存在着很大争论。虽然存在其它原因的可能性，但造成这种争论的根本原因在于贵州红色风化壳形成时代是依据其它资料(如夷平面、气候事件等)推断出来的，而不是根据直接测年数据界定的。因此，风化壳直接测年才是解决问题的关键。 本文在前人工作研究的基础之上，利用扫描电镜手段对贵州碳酸盐岩地区上覆风化壳土层中的石英颗粒进行观察、统计、分析，为风化壳成土的物质来源寻找新的证据；同时，经地球化学分析、测试等手段，判断风化壳土层中的晶体石英颗粒为风化壳形成初期的新生矿物——次生石英颗粒，并利用裂变径迹测年法对这种次生石英颗粒进行测年，最终探讨贵州碳酸盐岩地区上覆风化壳土层的形成年代。主要取得了以下几点认识： 一、石英颗粒蚀刻条件的优选 由于石英颗粒裂变径迹的长度和数量与晶格、铀含量、年龄等因素有关，所以不同地区的石英颗粒样品的裂变径迹蚀刻条件也存在差别；目前国际上有关石英颗粒的裂变径迹测年应用的实例较少，还没有统一的有关石英颗粒蚀刻条件的国际标准；现有的石英颗粒蚀刻条件有多种，但是缺乏对这些方法的优缺点进行对比评价。因此，我们要进行反复的条件实验，对比不同石英蚀刻剂的蚀刻效率，找寻适合石英颗粒的最佳蚀刻剂。实验结果表明，40%的HF溶液为最佳蚀刻剂，最佳蚀刻时间：温度在4℃左右（冬季）时为40min；温度在29℃左右（夏季）时为30min。 二、石英的外形、表面机械作用特征及其指示意义 我们利用扫描电镜对石英颗粒外形特征进行观察、统计、分析，结果表明本次研究的石英颗粒形态类型主要有两种：棱状-次棱状石英颗粒以及圆状、次圆状石英颗粒，其中棱状-次棱状石英颗粒包含了一部分晶体形态较为完整的石英颗粒。 根据石英颗粒表面机械作用特征分析结果，结合剖面区域地质特征，可初步判断剖面中的石英颗粒有三种物质来源：碳酸盐岩中的原生碎屑石英，有长时间长距离搬运特征；燧石团块石英，有短距离搬运或原位沉积特征；晶形较完整的次生石英，无搬运特征。三种石英均具有原位特征，前两种类型的石英是直接对基岩的继承，第三种类型的石英是风化壳剖面的次生矿物。 三、石英颗粒表面的化学作用特征及其风化强度指示意义 我们通过对石英颗粒表面化学作用形态的观察，发现大兴剖面、新蒲剖面和官坝剖面的石英颗粒表面化学溶解作用和化学沉淀作用都非常强烈，这表明三个剖面均处于湿、热环境中，均处于强烈的化学风化阶段。而且大兴剖面中石英颗粒表面的化学作用最强烈，气候较其他两个剖面更湿热，剖面的风化强度也最大，即各剖面的风化强度由强到弱排序为：大兴、新蒲、官坝。这一结果与矿物组成分析、化学风化强度、硅铝、铝铁硅风化系数比以及相对风化强度等的地球化学分析指标相一致，这也再次证明了我们采用石英颗粒表面形态特征分析手段的可行性和可靠性。 四、石英颗粒的裂变径迹年龄 三种类型石英颗粒的裂变径迹测年数据表明：a、同一样点石英颗粒裂变径年龄呈现一定的规律：F.T.AGE圆状、次圆状＞F.T.AGE不规则状（棱状、次棱状）＞F.T.AGE标准晶形（次生石英）。b、不同剖面的不规则状石英颗粒形成于同一个时期；不同剖面的圆状、次圆状石英颗粒形成于同一个时期。这两种石英颗粒不适于贵州碳酸盐岩风化壳的测年研究。c、不同剖面的标准晶形石英颗粒形成于不同时期，形成于碳酸盐岩酸不溶物原地堆积过程中，即与风化壳剖面同期形成，可用于贵州碳酸盐岩风化壳的测年研究。这一测量结果与我们对石英颗粒表面形态特征的观察、统计、分析结果相一致。 五、风化壳物源的新证据 贵州碳酸盐岩风化壳中的石英颗粒表面形态的分析结果表明，贵州碳酸盐岩风化壳的物质来源于碳酸盐岩中酸不溶物原地风化残积的产物，与其下伏基岩有着明显的继承性。这一分析结果与王世杰等人的碳酸盐岩酸不溶物的提取实验、地球化学、矿物学、粒度特征及区域地质背景等多方面的分析结果相一致，为贵州碳酸盐岩风化壳的物质来源及成因提供新的、更细致的证据。 六、贵州晚新生代地质-环境研究历史轮廓初建 由于目前对贵州及周边地区的风化-气候研究相对缺乏，数据资料较稀少，还没有形成完整的系统，我们本次研究也是建立在对风化壳中次生英颗粒年代学研究的基础上，研究还不是很透彻，因此只能对地质-环境研究历史轮廓进行初建。本文根据本次研究剖面土层中晶体次生石英颗粒的裂变径迹年龄分布情况，结合前人已有资料，对贵州25Ma以来的地质-环境演化历史的轮廓进行初建。从次生石英裂变径迹年龄值来看，中新世以来贵州主要经历了如下构造-风化期：25-19Ma、16-13Ma、10-6.5Ma、5-2Ma、1.7-1Ma。