Effects of light crude oil contamination on the physical and mechanical properties of geopolymer cement mortar

Fly ash and oil contaminated sand are considered as the two waste materials that may affect environment. This paper investigated the suitability of producing geopolymer cement mortar using oil contaminated sand. A comparison between physical and mechanical properties of mortar produced using geopolymer and Ordinary Portland Cement (OPC), in terms of porosity, hydration and compressive strength, was conducted. The results showed that heat curing can increase the compressive strength of geopolymer mortar up to 54% compared to ambient curing situation. The geopolymer mortar with 1% of light crude oil contamination yielded a 20% higher compressive strength than OPC mortar containing sand with a saturated surface dry condition. Furthermore, the formation of efflorescence decreased as the level of oil contamination decreased. Moreover, the heat curing method increased the kinetic energy and degree of reaction for geopolymer cement mortar, which cause an increment of the density of the pore system and improving the mechanical properties of the resulting composites. From the results of this study, it was demonstrated that geopolymer mortar has the potential of utilizing oil contaminated sand, and reducing its environmental impacts.     

减缩剂的作用及其机理

通过对减缩剂作用和机理的研究表明,减缩剂能较大幅度的降低干燥收缩和相对较小的提高塑性收缩抗裂能力,但在一定程度上降低了砂浆的力学性能.从塑性抗拉强度、表面水份蒸发率和孔结构三个角度对减缩剂的作用机理进行了试验分析,结果表明:减缩剂的加入能较显著的降低水溶液的表面张力,同时也降低了砂浆表面的塑性抗拉强度,增大了表面水份蒸发率,它对塑性收缩抗裂的效果取决于对塑性抗拉强度和毛细管收缩应力影响的权重;表面张力试验表明,减缩剂减小干缩的机理主要在于降低了孔溶液的表面张力;从对孔结构的分析表明,减缩剂掺入后增大了孔隙率,并增加了孔径＞0.1μm的孔的含量,从而降低了掺减缩剂的砂浆力学性能.     

Effect of latex and superplasticiser on Portland cement mortar in the fresh state

This report deals with the individual and combined effect of latex and superplasticiser on Portland cement mortar in the fresh state. The compatibility of five commercial superplasticisers with four latexes of the vinyl polymer group and SBR latex in varying dosages was studied with respect to setting time, consistency of fresh cement pastes, subjective workability (surface texture, segregation), bleeding, air content, water reduction capacity and the flow-time relationship of fresh mortar. It has been observed that superplasticisers of melamine formaldehyde and a blend of melamine and naphthalene formaldehyde eliminated shortcomings like delayed setting, high air entrainment in the fresh latex-modified system whereas lignosulphonate and a blend of lignosulphonate and naphthalene formaldehyde aggravated it. In a consequent report, performances in the hardened state will be discussed.     

盐冻条件下水泥砂浆受风沙冲蚀磨损性能及损伤机制

通过气流挟沙喷射法对水泥砂浆进行了复合盐-冻融循环后气-固两相流冲蚀磨损试验研究。基于SEM、激光共聚焦显微镜（LSCM）和XRD,观测了水泥砂浆试件冲蚀磨损后表面微观形貌,分析了盐冻前后其表面化学成分,探究其冲蚀损伤机制。结果表明：相同冲蚀试验条件下,水泥砂浆试件冲蚀率随冲蚀角度的增加而增大,在高冲蚀角下的增长趋势较为缓慢;冲蚀率随复合盐-冻融循环次数的增加出现先减小后增大的趋势,在冻融10次时冲蚀率最小;同等条件下,8%浓度下的冲蚀率均大于10%浓度下的冲蚀率。冲蚀损伤过程中动能法向分量起决定性作用,明显特征表现为冲蚀坑和微破坏区的出现。复合盐-冻融循环对冲蚀磨损性能的影响主要体现在两个方面：物理方面,表现为降温过程中溶液过饱和晶体析出以及冰胀压和渗透压对内部孔隙的作用;化学方面,溶液中的阴离子与水泥砂浆发生化学反应,生成钙矾石和石膏晶体填充在水泥砂浆内部,提高了其致密性,但后期晶体压力的增大会促进裂缝的产生,对水泥砂浆抗冲蚀磨损能力产生不利影响。     

Using the surface free energy method to evaluate the effects of liquid antistrip additives on moisture sensitivity in hot mix asphalt

The objectives of this research are to evaluate the susceptibility of aggregates and asphalt binder with and without liquid antistrip (LAA) additives to moisture damage based on the properties that affect the adhesion bond between the aggregate and asphalt binder and the cohesion strength of the asphalt binder using the surface free energy (SFE) concept and laboratory testing. The percentage of the aggregate surface area that was exposed to water (P) due to each cycle was used as a screening parameter for evaluating the compatibility of the asphalt binder and aggregates in terms of the resistance to moisture damage. The results show that adding LAA causes the total SFE of the asphalt binder to increase, which results in a decrease in stripping between the aggregate and asphalt binder in the presence of water. Similar results were obtained from a dynamic modulus test. From the data obtained, we conclude that LAA caused a reduction of the magnitude of P that improves its resistance to moisture damage.     

Simple methods to estimate the influence of limestone fillers on reaction and property evolution in cementitious materials

A commercial interest in sustainable cementing materials is driving efforts to reduce the use of cement in concrete. Limestone fillers are a promising direction towards achieving such cement use reductions. In spite of increasing filler use, little information is available to rapidly estimate the influences of limestone fillers, and more importantly filler fineness on reaction and property development. This work develops simple models to predict the effect of particle size classified limestone on hydration reactions and compressive strength development. The method builds on a relativistic basis, such that enhancements and alterations in reactions and properties are described in relation to a given control (pure cement) mixture. The prediction method considers aspects such as: (1) accelerations in reactions, (2) changes in inter-particle spacing as linked to the limestone filler’s fineness and (3) a porosity increase with increasing cement replacement. The predictive power of the approach is demonstrated for a variety of mixtures composed using three ASTM C150 compliant cements and forwards a basis for developing mixture proportioning strategies, such that apriori estimations of the mixture response (reaction rate and mechanical properties) can be used to optimize binder proportioning and thus strategize new methods to limit cement use in concrete construction applications.     

乳化液膜技术分离提取Cu2+的应用研究进展

乳化液膜技术是一种新型的分离提取技术．综述了乳化液膜技术在含铜废水处理、从铜矿石堆浸液中回收铜、湿法冶金中除铜以及痕量铜的富集与测定中的应用研究进展．目前，乳化液膜技术分离提取Cu^2 仍处于试验研究阶段，但近年来的应用研究表明，该项技术在分离提取Cu^2 方面具有广阔的应用前景．     

A mechanistic approach to evaluate the potential of the debonding distress in asphalt pavements

The debonding distress in asphalt pavement structures is a critical problem that affects the performance of asphalt concrete pavements. It occurs at the layer interface due to the poor bond quality between adjacent asphalt concrete layers and/or when stresses at the layer interface exceed the strengths of the material at the interface. The debonding of the adjacent layers, especially the top surface layer of an asphalt pavement, is a contributing factor to the premature cracking of pavements. Hence, the debonding distress can lead to a reduction in the life of the pavement. This paper presents an analytical and experimental framework to evaluate the potential for debonding at the layer interface of asphalt concrete pavements. Computational analysis was performed to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using the Layered ViscoElastic pavement analysis for Critical Distresses (LVECD) computer program developed at North Carolina State University. This computational analysis enables a greater understanding of the critical stress that is involved in debonding and the ways that such stress is affected by pavement design parameters and environmental conditions. In addition, a prediction model was developed that can determine the shear bond strength at the interface of asphalt concrete layers with different tack coat materials at various temperatures, loading rates and normal confining stresses. The systematic and mechanistic framework developed in this study employs the maximum shear ratio concept as a shear failure criterion and provides a tool to evaluate the effects of various loading, environmental and pavement factors on the debonding potential of asphalt pavements. The overall advantages of the mechanistic framework and approach using the LVECD analysis tool will help lead to better understanding of the debonding mechanism, proper selection of the tack coats, and economic benefit in highway pavement maintenance and rehabilitation costs.     

一种实车离合器操纵机构检测评价方法

针对目前离合器的力学特性在实车检测中仅仅依靠特性曲线相关特征点的位置作为其评价依据,未能充分利用特性曲线所给出的信息,进而可能导致出现误判的现状,提出一种新的评价方法.新方法通过分析离合器操纵机构阻尼在正程与回程之间的关系,发现离合器力学特性正程回程的算术平均值曲线与几何平均值曲线分处无阻尼曲线的上下方.经由试验与分析相结合的方法获取离合器无阻尼力学特性曲线,通过比较三条曲线是否满足应遵循的位置关系来判别离合器是否合格.实验结果表明,新方法的评价结果正确,且由于较充分地运用了特性曲线所给出的信息,从而大大降低了出现误判的概率.     

在NGOSS中综合应用策略管理和过程管理的方法

分析了NGOSS中策略管理和过程管理的互补性,研究了NGOSS中策略管理的策略间协作需求,提出了一种在NGOSS中综合应用策略管理和过程管理的方法,即运用过程管理来改进策略管理中存在的不足的方法,并对其进行了实验验证。实验证明,这种方法实现了NGOSS中策略之间的协作,改进了策略管理中存在的不足,实现了基于策略的“闭环”方式的管理系统,提高了NGOSS系统的管理功能。     

On the relation of setting and early-age strength development to porosity and hydration in cement-based materials

Previous research has demonstrated a linear relationship between compressive strength (mortar cubes and concrete cylinders) and cumulative heat release normalized per unit volume of (mixing) water for a wide variety of cement-based mixtures at ages of 1 d and beyond. This paper utilizes concurrent ultrasonic reflection and calorimetry measurements to further explore this relationship from the time of specimen casting to 3 d. The ultrasonic measurements permit a continuous evaluation of thickening, setting, and strength development during this time period for comparison with the ongoing chemical reactions, as characterized by isothermal calorimetry measurements. Initially, the ultrasonic strength-heat release relation depends strongly on water-to-cement ratio, as well as admixture additions, with no universal behavior. Still, each individual strength-heat release curve is consistent with a percolation-based view of the cement setting process. However, beyond about 8 h for the systems investigated in the present study, the various strength-heat release curves merge towards a single relationship that broadly characterizes the development of strength as a function of heat released (fractional space filled), demonstrating that mortar and/or concrete strength at early ages can be effectively monitored using either ultrasonic or calorimetry measurements on small paste or mortar specimens.     

井下乳化炸药混装车连续敏化器结构优化

为了使连续敏化器在较低的压降下实现乳化基质与敏化液的混合,以井下乳化炸药混装车的连续敏化器为研究对象,通过正交实验对不同结构的连续敏化器的内部流场进行数值模拟。结果表明连续敏化器的分流口直径对压降影响最明显,汇流口直径对混合效果影响最大,优化后的连续敏化器结构参数为分流口角度30°,分流口直径4 mm,汇流口直径6 mm,分流口数量4个。通过现场实验验证,优化后的连续敏化器满足乳化基质与敏化液的混合要求,相对于现有结构还降低了25%的流体压降。     

A novel method to measure the porosity of porous materials

ABSTRACT

Porosity is the single most important feature of porous materials. On the basis of the research work, a new method to measure the porosity of porous materials is proposed in this paper. This method is a system of equations composed of six formulas, so it is called model equation method. It is not only applicable to space holder technique but also applicable to metal prepared by pure powder metallurgy. Compared with mass volume method and immersion medium method, our new method is more simple and efficient. More importantly, it can be used as a standard measure. This study provides a fundamental basis for the measurement of porosity in porous materials.     

A method to evaluate the overall breakage degree of pre-weakening processing and its applications

The product fineness indicator t₁₀ and the pre-weakening degree indicator percentage change of A * b value (C_Ab) were used to described the two aspects of the breakage result of processing with pre-weakening effect. However, there lacks a method to evaluate the ‘overall’ breakage degree with a single index. It was observed that when the high voltage pulse breakage (HVP breakage or HVPB) induced cracks inside pre-weakened particles were consumed during impact breakage, the breakage characteristics of the progeny particles are the same to raw ore particles. Based on this phenomenon, the concepts of equivalent size S_ie and equivalent size reduction t_10e are proposed. Raw ore particles of size S_ie is ‘equivalent’ to pre-weakened particles of size S_i in terms of their impact breakage product size distribution. Therefore the value of S_i and the consequently derived t_10e can be used to evaluate the overall breakage degree of pre-weakened particles. The calculation procedure of S_ie and t_10e is demonstrated in the context of HVP breakage. It is found that the impact breakage product of pre-weakened particles can be well predicted from S_ie. In addition to the evaluation of overall breakage degree of pre-weakening processing, this method also has potential to apply in the simulation of comminution circuits with pre-weakening processing and the development of breakage model for processing with pre-weakening effect.     

Application of ground-penetrating radar in measuring the density of asphalt pavements and its relationship to mechanical properties

The ground-penetrating radar (GPR) is a proven technology that is used typically to determine the thicknesses of pavement layers. This paper explores the applicability of the GPR to assess the density of the asphalt layer in pavements. The measurements were conducted on three test sections that were constructed using different asphalt mixtures. Each of the test sections was divided into sub-test sections that were compacted using different compaction methods and number of roller passes in order to achieve a range of asphalt mixture densities. The results showed that there was very good correlation between the GPR results and density of extracted field cores. Consequently, the paper examines the correlation between density and mechanical properties of asphalt mixtures. The results of the mechanical tests provided valuable information on the effect of density on performance.     

一种改善高掺量碳纳米管/水泥砂浆性能的方法

碳纳米管(CNTs)在水泥砂浆中分散困难,并显著增加用水量,CNTs掺量较高时,水泥砂浆的各项性能显著降低。基于机械力-化学效应,利用粉煤灰的形态效应和二次水化特征,采用混磨工艺(MD)制成了粉煤灰-CNTs复合粉末,并将其制成CNTs-水泥砂浆(MCNT)。力学性能测试结果表明,MCNT的力学性能随着CNTs掺量的增加而增加。透射电子显微镜(TEM)和红外分析(FT-IR)测试结果表明,MD工艺使得CNTs表面接枝了粉煤灰活性组分,改善了CNTs-水泥的界面性能。场发射扫描电镜(SEM)测试结果表明,MD工艺实现了高掺量CNTs在水泥砂浆中的均匀分散。     

A novel method for determination of the filling level in the feed frame of a rotary tablet press

Aim: The aim of this study was to investigate whether the filling level within the feed frame of a rotary tablet press can be quantified by laser triangulation combined with the angle recognition of one paddle wheel via rotary encoder.

Significance: Rotary tablet press feed frames are supposed to assure a uniform die filling and, thus, to guarantee the weight and content uniformity of the resulting tablets. Therefore, a constant bulk availability and flow within the feed frame is crucial and has to be ensured by the feed frame design and the operating conditions. So far, there is no instrument available to monitor the bulk filling level or the bulk distribution within feed frames.

Methods: Calcium phosphate dihydrate was used as model powder. The powder surface level was determined via laser triangulation and the angle position of the paddle wheel was monitored via incremental rotary encoder. The data of both parameters was acquired synchronously and evaluated by in-house written software.

Results: Different powder masses led to significantly different filling level signals. The experiments showed a high reproducibility of the determined filling levels. Furthermore, an influence of the rotational speed on the powder distribution was observed.

Conclusions: The developed instrument may be used for quantification of the volumetric filling level within rotary tablet press feed frames. It may either be used to better understand the powder behavior within feed frames or for improvement of the die filling process by implementing the device into a feedback loop.     

A method to evaluate the tensile strength and stress-strain relationship of carbon nanofibers, carbon nanotubes, and C-chains

A method is introduced to assess the tensile strength of carbon nanofibers, carbon nanotubes (CNTs), and linear chains of carbon atoms (C-chains) obtained from thin amorphous carbon films by electron irradiation. Transmission electron microscopy images show that the nanofibers undergo a radiation-induced necking process, characterized by CNT formation and often followed by the formation of a C-chain. Simulations of the necking process are carried out to determine the tensile stress supported by the nanofiber and CNT neck.     

A simple test method,NAL-II,to evaluate the strength and elastic modulus of polymer matrix composite laminates

This study proposes and assesses a simple test method (NAL-II) to evaluate compressive properties of carbon fiber-reinforced polymer matrix composite laminates (CFRP). Compressive tests based on ASTM D6641 and NAL-II methods were conducted for direct comparison using three kinds of quasi-isotropic composite laminates (T800H/3633, T800S/3900-2B, and IM600/133). Stress–strain curves including the compressive modulus obtained using the NAL-II method showed good agreement with those obtained using the ASTM D6641. The NAL-II method gave slightly higher (approximately 10%) compressive strengths than the ASTM D6641 method, probably because of suppression of bending (buckling) before failure. The experimentally obtained results suggest that the NAL-II method can be useful for international standard testing of the non-hole compressive strength of CFRP laminates.