Recycling petroleum coke in blended cement mortar to produce lightweight material for Impact Noise Reduction

This work introduces a new way to use low-cost petroleum (pet) coke as lightweight aggregate in cement mortars to make sound barriers. The feasibility of adding pet coke in cement matrix was investigated: an in-depth characterization of as-received coke and the new lightweight mortar was made. The acoustic behaviour herein was assessed by constructing a large dimension mortar slab (made of cement and coke as aggregate) used as floor covering and measuring, according to the procedure described in international standards, the impact noise pressure level over the range of frequencies 100–5000 Hz. Impact Noise Reduction (INR) was also obtained and the results were compared to the ones experimentally obtained from a control mortar slab (made of cement and sand). Results showed that coke addition leads to a decrease in mechanical properties of resultant mortars, this is principally due to an increase of the porosity (～60%). A gradual increase of impact noise insulation was observed in lightweight floor covering from middle to higher frequencies tested, reaching, within this range, a remarkable improvement of sound insulation compared to control slab (～14 dB).     

Efficient utilization of cementitious materials to produce sustainable blended cement

To achieve sustainable development of cement industry, cementitious efficiency of different cement clinker and supplementary cementitious materials (SCMs) fractions, in terms of hydration process and strength contribution ratio, was characterized. The results show that blast furnace slag and steel slag should preferably be arranged in fine fractions due to their desirable hydration processes and high strength contribution ratios. Cement clinker should be positioned in intermediate fraction (8–24 μm) due to its proper hydration process. Replacement of cement clinker by SCMs with low activity or inert fillers in coarse fractions was also suggested, because coarse cement clinker fractions gave very low hydration degrees and little strength contribution. Both early and late properties of gap-graded blended cements prepared can be comparable with or higher than those of Portland cement, indicating both cement clinker and SCMs were used more efficiently. These blended cements also give additional cost savings and reduced environmental impact.     

Dredged sediments used as novel supply of raw material to produce Portland cement clinker

The maintenance of waterways generates large amounts of dredged sediments that are an environmental issue. This paper focuses on the use of fluvial sediment to replace a portion of the raw materials of Portland cement clinker, which would otherwise come from natural resources. The mineralogy of the synthetic cement was characterised using X-ray diffraction and scanning electron microscopy and its reactivity was followed by isothermal calorimetry. Comparisons were made to a commercial ordinary Portland cement (CEM I 52.5). Compressive strength measurements were conducted on cement pastes at 1, 2, 4, 7, 14, 28 and 56 days to study strength development. The results showed that Portland cement clinker can be successfully synthesised by using up to 39% sediment. The compressive strengths developed by the cement made from sediment were equivalent to those obtained with the reference at early ages and 20% higher at long term.     

Use of a kaolinitic clay as a pozzolanic material for cements: Formulation of blended cement

Local kaolinitic clay (from the region of Tabarka, Tunisia) was tested as a pozzolanic material. Thermal treatments were performed as a means of activation of the minerals. The phase identification, before and after heat treatment, was studied by X-ray diffraction and differential thermal analysis/thermogravimetric analysis (DTA/TGA).

In order to check the effect of three variables (the calcination temperature, the specific surface of the calcined clay and the percentage of incorporation of the heat treated clay in the formula of the blended cement) on the compressive strength of blended cement mortar bars at 7, 28 and 91 days, a Box–Behnken design was set up. It was concluded that the mechanical properties of the blended cements were mainly governed by the percentage of incorporation and the fineness of the calcined clay. It was also demonstrated that increasing the fineness of the calcined clay allowed for increases in the level of cement substitution. Finally, a blended cement composition has been formulated, with optimal results at calcining temperature 700 °C, 30% of calcined clay ground at a Blaine fineness of 7700 cm²/g.     

Use of mineral admixtures to prevent thaumasite formation in limestone cement mortar

Concrete made from limestone cement may exhibit a lack of durability due to the formation of thaumasite. The addition of minerals that improve the concrete durability is expected to slow down the formation of thaumasite. In this work the effect of natural pozzolana, fly ash, ground granulated blastfurnace slag (ggbs) and metakaolin on the thaumasite formation in limestone cement mortar is examined. A limestone cement containing 15% w/w limestone was used. Mortar specimens were prepared by replacing a varying part of the limestone cement with the above minerals. Siliceous and calcareous sand was used in order to study the effect of the sand type on the thaumasite formation. The specimens were immersed in a 1.8% MgSO₄ solution and cured at 5 and 25 °C. The formation of thaumasite was checked and confirmed by visual inspection, strength tests, ultrasonic pulse velocity measurements, XRD and TGA. It is concluded that the use of specific minerals, as partial replacement of cement, inhibits the thaumasite formation in limestone cement mortar.     

Electrical and Acoustic Emissions in cement mortar beams subjected to mechanical loading up to fracture

The application of mechanical loading on cement-based materials generates weak electrical currents due to the formation and propagation of microfractures. This paper introduces the simultaneous recording of electrical signal emissions know as Pressure Stimulated Currents (PSCs) and Acoustic Emissions (AEs) detected in cement mortar beams of rectangular cross-section subjected to mechanical loading using the Three Point Bending tests. The rate of the applied load during the experiments was constant up to the fracture of the specimen. The characteristics of the AE and PSC were put in contrast in order to better understand the evolution of the microfracture processes up to fracture. Specifically, the recorded PSC and AE were studied in terms of their time series, cumulative energy along with AE rate and AE interevent times that may provide information about the upcoming specimen fracture. Moreover, non-extensive statistical physics modeling was attempted in terms of studying the Tsallis entropy. Specifically, the entropic index q was calculated and its dependence on the applied mechanical load was investigated.     

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。     

Use of pre-wetted lightweight fine expanded shale aggregates as internal nutrient reservoirs for microorganisms in bio-mineralized mortar

Interest in developing bio-based self-healing cement-based materials has gained broader attention in the concrete community. One of challenges in developing bio-based self-healing cement-based materials is that cell death or insufficient metabolic activity might occur when the cells are inoculated to the cement paste. This paper investigates the use of internal nutrient reservoirs via pre-wetted lightweight fine expanded shale aggregates to improve cell viability in mortar. Incorporation of internal nutrient reservoirs resulted in an increase in the vegetative cells remaining without any substantial loss in strength. These results pave the way to develop a self-healing and self-curing concrete with an extended service life.     

Effect of water-retaining lightweight aggregate on the reduction of thermal expansion coefficient in mortar subject to temperature histories

Cement paste containing blast furnace slag with a water to binder ratio of 0.40 showed considerable increase in thermal expansion coefficient due to self-desiccation. Hence the control of thermal expansion coefficient by internal curing with light weight aggregate was studied.Three types of fine aggregate, hard sandstone, oven-dry light-weight aggregate (LWA) and water-saturated LWA, and three temperature histories were applied to the mortar specimens with a ground granulated blast furnace slag. Total strains and time-dependent thermal expansion coefficients of the mortar specimens were determined using a newly developed setup comprising a specimen temperature regulator and measuring devices for dimensional change of the specimen. As the experiments of total strain and time-dependent thermal expansion coefficient have shown, the water-saturated LWA was able to control the time-dependent thermal expansion coefficient during the temperature history and could be favorably applied to massive concrete undergoing considerable thermal strain. The effectiveness of water-saturated LWA was found to be valid not only for autogenous shrinkage but also for thermal strain produced by the change in thermal expansion coefficient during the temperature history. These strains have been separated from the total strain by the proposed method.     

Effect of water-retaining lightweight aggregate on the reduction of thermal expansion coefficient in mortar subject to temperature histories

Cement paste containing blast furnace slag with a water to binder ratio of 0.40 showed considerable increase in thermal expansion coefficient due to self-desiccation. Hence the control of thermal expansion coefficient by internal curing with light weight aggregate was studied.Three types of fine aggregate, hard sandstone, oven-dry light-weight aggregate (LWA) and water-saturated LWA, and three temperature histories were applied to the mortar specimens with a ground granulated blast furnace slag. Total strains and time-dependent thermal expansion coefficients of the mortar specimens were determined using a newly developed setup comprising a specimen temperature regulator and measuring devices for dimensional change of the specimen. As the experiments of total strain and time-dependent thermal expansion coefficient have shown, the water-saturated LWA was able to control the time-dependent thermal expansion coefficient during the temperature history and could be favorably applied to massive concrete undergoing considerable thermal strain. The effectiveness of water-saturated LWA was found to be valid not only for autogenous shrinkage but also for thermal strain produced by the change in thermal expansion coefficient during the temperature history. These strains have been separated from the total strain by the proposed method.     

Experimental determination of fracture parameters for crack propagation in hardening cement paste and mortar

For all cement-based composite materials, hardening cement paste and mortar are the matrix materials. Their fracture properties are the basis for studying the fracture characteristic of cement-based composite materials. Therefore, three-point bending beams with three different sizes and three different strengths were tested to study the basic fracture properties of hardening cement paste and mortar. Corresponding values of load (P), crack mouth opening displacement (CMOD), and loading point displacement (δ) were simultaneously recorded. The initial cracking load P _ini was determined by using resistance strain gauges making up a full-bridge circuit, and the crack propagation process was observed during the test. It was found that the fracture behavior of both hardening cement paste and mortar are not brittle fracture and show a steady crack propagation process before the peak load was reached. This means that the fracture behaviors of all cementitious composites are nonlinear, even hardening cement paste and mortar. Therefore, corresponding fracture parameters of the hardening cement paste and mortar were determined using the double-K fracture model. The results indicate that this model is applicable to hardening cement paste and mortar. In addition, according to the principle of work of fracture, fracture energy values of the tested hardening cement paste and mortar were calculated after taking into account the contribution of the tail of the P–δ curve on fracture energy.     

Validation of Model Order Assumption and Noise Reduction Method for the Impact Resonance Testing of Asphalt Concrete

The impact resonance test is a free vibration-based nondestructive test method that has been increasingly used in evaluation and characterization of asphalt concrete for the past two decades. The rheological modeling of the impact resonance test is conceptualized by a linear viscous damping mechanism having single degree of freedom whose equation of the motion is assumed to be second order. In this study, the second order equation of motion assumption in the modeling of the impact resonance test response was evaluated for asphalt concrete testing. A set of asphalt concrete specimens was tested with the impact resonance test, and the obtained signals at a range of temperatures were evaluated by means of the Hankel matrix method. The results showed that the assumption is violated for asphalt concrete testing especially at high temperatures, mainly due to the presence of noise in the obtained response. However, the Hankel method was employed to filter out the noise. It was seen that the assumption could be employed for asphalt concrete at a range of temperatures including high temperatures, provided that the filtering is performed on the obtained signal. The results also showed that the employed filtering procedure produced improvements for the impact resonance test material dependent responses, resonant frequency and especially damping ratio calculations.     

Studies on potential of Portland cement mortar for binding of waterworks sludge to reduce heavy metal leaching

The investigation of heavy metal leaching and physicochemical properties of cement-solidified waterworks sludge (CMWWS) formed by incorporating waterworks sludge (WWS) into cement mortar was carried out. The chemical composition, compressive strength and other physicochemical properties of the CMWWS cube specimens were determined using field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD) and Fourier transform-infrared spectroscopy (FTIR). The major type of chemical components present in CMWWS was found to be Al and Fe. The increasing amount of WWS added to cement mortar resulted in the increasing of organic matter, urchin-like morphology and clear peak intensity. At the end of 28 days of curing, the soaking solution became strongly basic and CMWWS cube specimens leached out higher amount of heavy metals. The compressive strength of CMWWS increased up to a WWS percentage of 10%, and basic (pH > 7) curing solution was found to be better than water for curing purposes. It is concluded that solidification–stabilisation (S/S) technique is able to effectively reduce the leaching of heavy metals from the WWS and CMWWS containing up to 10% WWS can be used as construction material.     

铁路客运专线吸声式声屏障降噪研究

声屏障是隔断客运专线环境噪声传播途径的降噪方式之一,工程上常用的计算声屏障插入损失的方法是基于演算性质的方法,很难实现声屏障的精确设计。为了预测铁路客运专线声屏障的降噪效果,利用边界元法建立铁路客运专线声屏障降噪预测模型,对声屏障插入损失进行数值计算。研究结果表明：（1）声屏障对高频噪声辐射的降噪效果比低频噪声的要好;（2）客运专线声屏障由于吸附材料的不同,它们的降噪效果表现得都不同。     

货运调车场减速顶噪声及治理的探讨

铁路货物运输枢纽的调车场中，驼峰调车是主要的调车手段，为提高生产效率和确保安全，沿驼峰下滑道布置的减速器（减速闸，减速顶）的噪声是调车场噪声的主要声源之一，本文通过对昆明东站铁路降噪工程的观测试验项目，探讨了减速顶噪声的特性及治理措施。     

A novel method to evaluate the setting process of cement and asphalt emulsion in CA mortar

Cement and asphalt mortar (CA mortar) is the key component in the structure of Shinkansen slab track and serves as the elastic shock-absorber. A new method was put forward to evaluate the setting process of cement and asphalt emulsion (CAE) in CA mortar. It was noted that the setting process was governed by several factors such as cement types, cement/asphalt emulsion ratios (C/AE ratio). Results also indicated that the setting process of CAE was faster, the higher proportion of cement content was; the early age strength and the separation rate of CA mortar could be improved by using cement of high early age strength and rapid hydration rate, or a blended cement with ordinary Portland cement partially replaced by sulfoaluminate cement, or by increasing C/AE ratio. Nevertheless, the replacement ratio of ordinary Portland cement by sulfoaluminate cement should not exceed 15% and C/AE ratio should be not less than 0.8.     

Optimal Slot Numbers for Magnetic Noise Reduction in Variable-Speed Induction Motors

Although many empirical rules have been established for correctly choosing the number of stator and rotor slots so as to limit the audible magnetic noise level radiated by induction machines, these rules never take into account the stator natural frequencies or the fact that the motor is run at variable speed. In this paper, we present a fast simulation tool for the variable-speed magnetic noise emitted by induction machines, based on fully analytical models. On the basis of these models, we derive and experimentally validate an analytical expression for magnetic vibrations due to slotting reluctance harmonics, confirming the prime importance of slot combination in magnetic noise radiation. We ran simulations on a 700-W squirrel-cage motor in order to quantify the noise emitted by all possible combinations of slot numbers in two- and three-pole pairs, including odd slot numbers. We thus obtained a database that efficiently replaces the old empirical rules for slot combination numbers and helps in designing quiet induction motors. Similar databases can be built for other power ranges.      

Characterization and Reduction of Magnetic Noise Due to Saturation in Induction Machines

This paper derives the analytical characterization of Maxwell radial vibrations due to saturation effects in induction machines, and especially in traction motors. The number of nodes and the velocity of these particular force waves are experimentally validated by visualizing some operational deflection shapes of the stator. It is shown that according to the stator and rotor slot numbers, and stator natural frequencies, these forces can be responsible for high magnetic noise levels during starting and braking. A simple rule to avoid saturation magnetic noise is then proposed, and applied to an industrial motor. Simulation results show that the new proposed motor improves magnetic noise level up to 20 dB, whereas experiments give a 15 dB improvement.      

Composition of lime-cement and air-entrained cement mortar as a function of distance to the brick-mortar interface: consequences for masonry

The composition of a lime-cement mortar and an air-entrained cement mortar was studied as a function of distance to the brick-mortar interface. Both mortars had the same cement-to-sand ratio and the same water-to-cement ratio; in the lime-cement mortar the binder-to-sand ratio was highest. The measurements indicate that the mortar composition (i.e. the contents of sand, cured binder and voids) and the contents of chemical substances of the cured binder (i.e. the contents of calcite, portlandite and ettringite) change with distance to the brick-mortar interface. For the mortar composition the tendency of these changes is the same, but for the contents of the chemical substances of cured binder for the two mortar types the tendency of these changes is opposite and also the extent of the changes is significantly different. For the air-entrained cement mortar, the observations are explained by the enrichment of binder towards the brick-mortar interface, resulting from the compaction of fresh mortar. In the lime-cement mortar such an enrichment of binder hardly occurs and the observations are explained by the intense carbonation that takes place. As a result, the contents of the chemical substances in the mortars is very much different. In the air-entrained cement mortar, near the brick-mortar interface the enrichment of cement and the low water content (resulting from the low water retentivity of this mortar), lower the water-to-cement ratio and as a consequence the cement is not fully hydrated. In the lime-cement mortar, as the Ca(OH)₂ content and the water content is higher, near the brick-mortar interface, a carbonated zone is formed which is hardly permeable for CO₂ (and probably water). This does not occur in the air-entrained cement mortar, it remains permeable.