Different Types Of Aggregates Research Articles

Fracture modelling of normal concrete using different types of aggregates

It is a challenging task to take into account the type and form of aggregate in the numerical modelling of concrete. Discrete Element Method (DEM) offers the possibility to consider these properties via its model parameters. However, to get a usable model for further purposes, these model parameters first have to be calibrated precisely, based on laboratory measurement data. The model calibration is a time consuming process that requires high computational resources. In this study, an estimation model is proposed to define the model parameters of a DE model in function of the properties (density, compressive strength, particle size distribution, etc.) of the real material. The proposed model contained a number of factors and constants which were optimized based on our measurements. The measurements were carried out on samples produced from seven different concrete mixes. The mixes differed from each other in the type of the aggregate (quartz gravel, crushed stone, expanded clay) or in their particle size distribution (A or C grading curves, no-fines). The estimation model, with the optimized parameters, was applied on a test data set. The results indicated that the estimation model was able to estimate the DE model parameter properly. By estimating the DE model parameters more precisely at the start of the calibration process, it is possible to save significant amount of time and make the modelling more productive. The accuracy of the estimation model can be further increased by considering the aggregate-to-cement (a/c) ratio of concrete which is difficult to be determined in case of a hardened concrete sample whose concrete mix composition is unknown. An image processing technique is applied in this study to determine the a/c ratio. The results showed that the thresholding method is an appropriate alternative to determine the a/c ratio of various concrete mixes.

Proposed models for concrete thermal expansion with different aggregate types and saturation conditions

The Coefficient of thermal expansion (CTE) for concrete is one of the most important parameters that affect the fire performance of concrete. Concrete’s coefficient of thermal expansion is controlled by the CTE of each component of the concrete mix, as the coarse aggregates represent the largest portion in the concrete mix, it is considered to have a significant effect on the CTE for concrete. Another factor that affects concrete’s CTE significantly is the saturation condition (saturated, partially saturated and oven dried condition). This paper presents reviews for available tests results that have been conducted on the CTE for concrete at elevated temperatures for different aggregates type, these results are used to evaluate the models proposed by ASCE model and Euro Code. The results included the coefficient of thermal expansion for different types of aggregates in different saturation conditions (saturated, partially saturated and oven dried condition). It is found that there is a significant difference between the experimental results and Euro code carbonate model, Euro code siliceous model and ASCE. New models were proposed for predicting CTE of different types of aggregate under different saturation condition. The newly proposed models give better prediction compared to Euro code and ASCE model.

Influence by chemical constitution of aggregates on demulsification speed of emulsified asphalt based on UV-spectral analysis

Emulsified asphalt as an indispensable raw material for pavement engineering construction is subjected to various combinations of aggregates and varying environmental conditions leading to uncontrollable demulsification speed. In this respect, this research examined the influence of chemical composition of aggregate on emulsified asphalt demulsification speed. Three representative types of domestic road limestone aggregates with various appearances were studied by chemical analysis method. Experimental results indicate that the Magnesium oxide, alumina, calcium oxide, ferric oxide and silicon oxide were the main chemical compositions of limestone aggregate and their contents varied significantly among different types of aggregate. Ultraviolet spectrophotometry was used to evaluate effects of each chemical component on the demulsification speed of emulsified asphalt. Results indicate that mixing ratio of chemical components has a significant effect on demulsification speed of asphalt emulsion. Magnesium oxide accelerated the demulsification speed of emulsified asphalt, while calcium oxide showed an opposite trend. Iron oxide, alumina and silica had little effect on the speed of demulsification. Finally, grey correlation analysis was performed, and a clear relationship was established. The results which are expressed as the magnesium oxide, alumina, iron oxide and silicon dioxide content with differing ratio in the aggregate affected significantly on the demulsification speed of emulsified asphalt. However, there is no clear relationship between the demulsification speed and emulsified asphalt when the ratio of the calcium oxide content is changed.

The Geology, Stratigraphy and Structure of Ma’an Area, South

This study focused on the geology, stratigraphy and structure of the Ma'an area at the coordinates: 350 30/350 45 / E 300 00/-300 15/ N. Field and laboratory studies have been carried out with aim to get a better understanding on the main geological features at the study area. Therefore, the importance of this study is due to the fact that Jordan is witnessing an expansion in investment in the extractive and exploration industries, and Ma'an Governorate is considered as a huge reservoir of mineral and industrial rocks that will play an important role on mining industries in Jordan. Rocks like phosphate, limestone, coquina, clay, dolomite, sandstone and different types of aggregates are the main source for many industries in the area.The study area is located at 210 km south of Amman and is covered mainly by sedimentary rocks. This study includes a detailed explanation of the sedimentary rocks covering the whole area, including the Ajloun group which consist the Wadi Sir Limestone Formation, and the Balqa group which consist the following formations: Umm Al-Ghudran, Amman Silisicified Limestone, Al Hisa Phosphorite, Muwaqqar Chalk Marl and Umm Rijam Chert Limestone, as well as the lake sediments which appear in different localities in the study area .The study also includes the most important geological structures, where the most prominent direction of these structures are the north-south, northeast-southwest, northwest and southeast faults, with few folds in different parts of the region. Keywords: Ma’an, sedimentary, formation, lake, structure DOI : 10.7176/JEES/9-3-10 Publication date :March 31 st 2019

Evaluation of experimental testing methods for the design of permeable friction course mixtures

Since the first mix design of the permeable friction course (PFC), there are currently more than 20 methods used to design PFC mixtures, and thus it is important to evaluate these methods for optimum design. This paper compares the differences of several critical procedures specified in the main design methods of PFCs and their effects on performances, specifically the procedures of specimen compaction (Marshall compaction and Superpave Gyratory Compaction), the draindown test (beaker method, test pan method, and wire basket method), the theoretical maximum specific gravity assessment (vacuum saturation, solvent immersion, and asphalt immersion), and the bulk specific gravity assessment (dimension analysis and corelok method). The effects of different types of aggregates and test methods on properties of PFC mixes were investigated, and it was found that the testing results acquired by different test methods were clearly different. The wire basket, asphalt immersion, and corelok methods all showed better performances for PFC mixes than the others.

Preparation of Self-Assembled Composite Films Constructed by Chemically-Modified MXene and Dyes with Surface-Enhanced Raman Scattering Characterization.

The effective functionalization and self-assembly of MXene are of crucial importance for a broad range of nanomaterial applications. In this work, we investigated the aggregates of sulfanilic acid-modified MXene (abbreviated as MXene-SO3H) with three model dyes at the air–water interface and demonstrated the morphological and aggregation changes of composite films, using Langmuir-Blodgett (LB) technology, as well as excellent uniformity and reproducibility by using surface-enhanced Raman scattering (SERS) spectra. This research has found that cationic dye molecules were adsorbed onto negatively charged MXene-SO3H particles mainly through electrostatic interaction and the particles induced dyes to form highly ordered nanostructures including H- and/or J-aggregates corresponding to monomers in bulk solution. The surface pressure-area isotherms from different dye sub phases confirmed that the stable composite films have been successfully formed. And the spectral results reveal that different dyes have different types of aggregations. In addition, the SERS spectra indicated that the optimal layers of MXene-SO3H/methylene blue (MB) films was 50 layers using rhodamine 6G (R6G) as probe molecule. And the formed 50 layers of MXene-SO3H/MB films (MXene-SO3H/MB-50) as SERS substrate were proved to possess excellent uniformity and repeatability.

Effect of Aggregates on the Technological and Mechanical Properties of Glass and Basalt Fibres Reinforced Concrete

Reinforcement of high performance concrete (HPC) with glass and basalt fibres is becoming more widely used due to their high mechanical properties, sustainable manufacturing process and wide range of application in architectural and urban design. Properties of HPC composites are mainly determined by matrix composition, fibre type, volume and distribution in the concrete matrix. Granulometry and shape of aggregates has a major impact on the technological properties of concrete mix, such as water bleeding and slump size. Current study is focused on investigation of HPC reinforced by glass and basalt fibres with aggregates of different types. Quartz sand and crushed granite were used as aggregates. Two matrix compositions were used, both having proportion 1:1 of ordinary Portland cement (OPC) and total amount of aggregate. In the first case, the whole aggregate was quartz sand, and for the second it was 50% quartz sand and 50% crushed granite. For matrix reinforcement, 3% of alkali resistant glass fibres and 1.5% chopped basalt from total weight of dry materials were used. 1% from cement mass of polycarboxylate ether-based superplasticizer was used to increase workability of concrete mix. The consistency of mixtures decreased, but flexural strength increased approximately by 13% when 50% of quartz sand was replaced with crushed granite for concrete with both types of fibres.

Development and validation of an enhanced test setup for assessing HMA stripping potential under hydrodynamic pressure

A custom enhanced and modified Rice test setup was utilised in this laboratory study to assess and quantify the moisture sensitivity of hot-mix asphalt (HMA) under hydrodynamic pressure testing. The hydrodynamic pressure was simulated by repeatedly alternating the pumping and vacuum suction forces, which separately represented the positive and negative pore pressure on the HMA under a hypothetical combined action of moving vehicles and moisture effects. The overall research approach involved the following sequence of work activities: freeze-thaw and Hamburg wheel track testing for hydrodynamic pressure simulative effects, X-ray fluorescence analysis for stripped and suspended material identification followed by the development of the anti-stripping test (i.e. the enhanced/modified Rice test setup) and sensitivity analyses. In the study, laboratory validity of the new anti-stripping test was preliminary and successfully demonstrated through moisture sensitivity evaluation and analyses of various HMA with different types of aggregates (limestone, diabase, and basalt), asphalt binders (AH-70, SK-70, and styrene-butadiene-styrene (SBS)), and fillers (limestone mineral powder, hydrated lime, and brake pad waste (BPW) powder). For the aggregates, the rank order of superiority in terms on moisture resistance was found to be basalt (best) followed diabase and lastly limestone (poorest). As theoretically expected, the SBS-modified asphalt binder out-performed the AH-70 and SK-70 asphalt binders in terms of resistance to moisture damage, while the BPW powder demonstrated superiority over the other fillers, with the limestone mineral powder being the poorest.

Measuring emotions during learning: lack of coherence between automated facial emotion recognition and emotional experience

AbstractMeasuring emotions non-intrusively via affective computing provides a promising source of information for adaptive learning and intelligent tutoring systems. Using non-intrusive, simultaneous measures of emotions, such systems could steadily adapt to students emotional states. One drawback, however, is the lack of evidence on how such modern measures of emotions relate to traditional self-reports. The aim of this study was to compare a prominent area of affective computing, facial emotion recognition, to students’ self-reports of interest, boredom, and valence. We analyzed different types of aggregation of the simultaneous facial emotion recognition estimates and compared them to self-reports after reading a text. Analyses of 103 students revealed no relationship between the aggregated facial emotion recognition estimates of the software FaceReader and self-reports. Irrespective of different types of aggregation of the facial emotion recognition estimates, neither the epistemic emotions (i.e., boredom and interest), nor the estimates of valence predicted the respective self-report measure. We conclude that assumptions on the subjective experience of emotions cannot necessarily be transferred to other emotional components, such as estimated by affective computing. We advise to wait for more comprehensive evidence on thepredictive validityof facial emotion recognition for learning before relying on it in educational practice.

长江流域景观格局与生态系统水质净化服务的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 长江流域景观格局与生态系统水质净化服务的关系 DOI: 10.5846/stxb201801130100 作者: 作者单位: 中国科学院生态环境研究中心,中国科学院生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0503401）；中国科学院科技服务网络计划项目（KFJ-STS-ZDTP-022） Relationships between landscape pattern and ecosystem water purification service in the Yangtze River Basin Author: Affiliation: Research Center for Eco-Environmental Sciences,Research Center for Eco-Environmental Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:流域景观格局通过影响生态过程，改变进入河流污染物的数量，进而对水质净化服务产生重要影响，探讨流域景观格局对水质净化服务的影响对于流域景观规划、生态系统保护和生态系统服务提升具有重要意义。以长江流域为研究区域，在分析45个子流域景观格局特征、应用InVEST模型评估流域水质净化服务基础上，探讨了两者的关系，结果表明：①景观组成上，长江流域农田和城镇面积比例分别与生态系统水质净化服务存在显著对数关系（P < 0.01），森林面积比例则与之呈极显著正相关关系（P < 0.01）；②流域景观配置上，斑块密度和景观破碎度与水质净化服务呈显著负相关（P < 0.01），而平均斑块面积和形状规律相反（P < 0.01）；③斑块类型水平上，森林平均斑块面积、灌丛/湿地平均斑块形状与生态系统水质净化服务呈显著正相关（P < 0.01），而农田平均斑块面积/边缘密度、城镇斑块密度则与之呈显著负相关（P < 0.01）；④森林主导景观的子流域，仅有景观破碎度与生态系统水质净化服务呈显著负相关，而农田主导景观的子流域，景观蔓延度、香农多样性与其分别呈正相关（P < 0.01）。研究结果可以为长江流域生态系统水质净化服务的提升提供多途径的管理信息：流域景观尺度上，增加森林面积比例、控制农田与城镇面积比例，并减少景观破碎度而增加平均斑块形状复杂性；斑块类型水平上，可增加灌丛/湿地斑块形状复杂性，减小农田边缘密度和城镇斑块密度；森林主导景观的子流域应降低景观破碎度，以农田主导景观的子流域则应该增加斑块类型丰富度和团聚程度。研究也可为其他流域水质净化服务管理提供参考。 Abstract:Landscape patterns can affect pollutant discharge into rivers by influencing ecological processes, and further affect water purification service of ecosystems in the watershed. It is of great significance for landscape planning, ecosystem protection, and ecosystem services promotion to explore the relationships between landscape patterns and ecosystem water purification service. The landscape pattern characteristics were analyzed and ecosystem water purification service was assessed by using InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model in 45 sub-basins of the Yangtze River Basin. Then the relationships between landscape patterns and ecosystem water purification service were identified. For the landscape composition, the proportions of farmland and urban areas were logarithmically correlated with ecosystem water purification service (P < 0.01), whereas the proportion of forest area was positively correlated with it (P < 0.01). For the landscape configuration, water purification service was negatively correlated with patch density and landscape fragmentation, and positively correlated with the average patch area and shape (P < 0.01). For the patch-type, average patch area of forest/shrub and the average patch shape of shrub and wetland were positively correlated with ecosystem water purification service, while the average patch area and edge density of farmland and urban patch density were negatively correlated with water purification service (P < 0.01). Only landscape fragmentation and the ecosystem water purification service was negatively correlated in the forest-dominated sub-basin (P < 0.01). In the farmland-dominated sub-basin, ecosystem water purification services were positively correlated with landscape aggregation and Shannon diversity indexes (P < 0.01). The above results can provide management information for the promotion of ecosystem services in the Yangtze River basin. At the landscape scale of the basin, increasing the area proportion of forest, controlling the farmland and urban area proportions, reducing the landscape fragmentation, and increasing the complexity of the average patch shape would be helpful for the improvement of ecosystem water purification service. At the patch-type level, increasing the area of the shrub patch and the shape complexity of the shrub and wetland patches, and reducing the edge density of urban and the patch density of farmland would also contribute to the promotion of ecosystem water purification service. In the forest-dominated sub-basins, landscape fragmentation should be prevented, while the diversity and aggregation of different types of patches should be increased in the farmland-dominated sub-basins. The information can also provide important for the management of ecosystem water purification service in other basins. 参考文献 相似文献 引证文献

Effect of different expanded aggregates on the properties of lightweight concrete

Lightweight aggregate concrete is a material which has much lower density than normal concrete and many advantages, including advanced insulation performance due to its highly porous or cellular characteristics. Several types of lightweight aggregates have been used to produce lightweight aggregate concrete, and the characteristics of such lightweight aggregates strongly affect the material properties. In this study, three different expanded materials – expanded glass (Liaver), expanded clay (Liapor) and foam glass (Ecoglas) – were utilised as lightweight aggregates, and their effects on the properties of lightweight concrete were investigated. These expanded lightweight aggregates are light and have lower thermal conductivity as well as water absorption than those of normal aggregates. Microstructural characteristics of the specimens with different types of aggregate were examined using X-ray micro-computed tomography. The thermal (thermal conductivity) and mechanical (compressive strength) properties of the lightweight concrete specimens were evaluated experimentally and numerically. The relationship between the physical properties and characteristics was analysed to demonstrate the effect of each expanded aggregate on lightweight aggregate concrete.

The Effect of Petrographic Characteristics and Physico-Mechanical Properties of Aggregates on the Quality of Concrete

This paper examines the effect of the aggregate type on concrete strength, and more specifically, how the petrographic characteristics of various aggregate rocks as well as their physico-mechanical properties influences the durability of C 25/30 strength class concrete. The studied aggregate rocks were derived from Veria-Naousa and Edessa ophiolitic complexes as well as granodiorite and albitite rocks from their surrounding areas in central Macedonia (Greece). Concretes were produced with constant volume proportions, workability, mixing and curing conditions using different sizes of each aggregate type. Aggregates were mixed both in dry and water saturated states in concretes. Six different types of aggregates were examined and classified in three district groups according to their physicomechanical properties, petrographic characteristics and surface texture. The classification in groups after the concrete compressive strength test verified the initial classification in the same three groups. Group I (ultramafic rocks) presented the lowest concrete strengths, depending on their high alteration degree and the low mechanical properties of ultramafic aggregates. Group II (mafic rocks and granodiorite) presented a wide range of concrete strengths, depending on different petrographic characteristics and mechanical properties. Group III (albite rocks) presented the highest concrete strengths, depending on their lowest alteration degree and their highest mechanical properties. Therefore, mineralogy and microstructure of the coarse aggregates affected the final strength of the concrete specimens.

Aggregation behaviour of tetracaine hydrochloride with Gemini surfactants and the formation of silver nanoparticles using drug-Gemini surfactants mixture

This study aimed to encapsulate drug into the silver nanoparticles (AgNPs) by using drug-Gemini surfactant mixed aggregate. The applicability of drug-surfactant based AgNPs is to carry the maximum amount of drug during the drug delivery process. The nano-size mixed aggregate was prepared by a local anaesthetic amphiphilic drug, tetracaine hydrochloride (TC) and Gemini surfactants, pentamethylene-1, 5-bis(tetradecyldimethylammonium bromide) (GS-5, 14-5-14) and hexamethylene-1,6-bis(tetradecyldimethylammonium bromide) (GS-6, 14-6-14). Surface tension and conductance measurements were used to determine the physiological and thermodynamic interaction parameters of TC-GS-5/GS-6. The negative βm values suggested as the synergistic interactions observed between TC and GS-5/GS-6 mixed aggregate. The TC-GSs mixture was used to stabilizing silver nanoparticles (AgNPs) with a different mole fraction αTC 0.0–0.99 in aqueous media. The resulting AgNPs characterized by UV–Vis spectroscopy and transmission electron microscopy (TEM). Dynamic light scattering (DLS) suggested that the different types of aggregate formed in aqueous media depending on the internal packing arrangements of TC-GS-5/GS-6. The mole fraction base formulation of drug-surfactant could control the mixed aggregates which could be used to formed drug-surfactant based nanoparticles to enhance the performance of drug delivery.

The production cycle of lime‐based plasters in the Late Roman settlement of Scauri, on the island of Pantelleria, Italy

AbstractThis paper deals with the archaeometric study of lime‐based plasters found in the archaeological settlement of Scauri, located in the homonymous bay in the south‐western part of Pantelleria Island. Since 1999, archaeological surveys have led to the recovery of the huge remains of a Late Roman settlement dating back to the fourth–fifth century AD. It is well known that the island of Pantelleria is entirely composed of volcanic rocks. Accordingly, the production of quicklime required calcareous rocks to be imported. Also, the selection criteria of the sandy aggregate are relevant and of interest to this study, to evaluate the achieved technological level. Within this context, a mineralogical and petrographic characterisation of the plasters was carried out using thin‐section petrography, for the classification of the sand aggregate. Moreover, X‐ray diffraction and scanning electron microscopy were performed to investigate the composition of the binder. The analytical results allowed the identification of different recipes for the manufacture of the studied plasters, obtained by the use of different types of aggregate (volcanic rock fragments, pumice, basaltic scoriae, and ceramic fragments) and highlighted the degree of pozzolanic reaction of the binder. Finally, the provenance of the calcareous raw material was inferred using a petrographic approach.

Influence Analysis and Optimization for Aggregate Morphological Characteristics on High- and Low-Temperature Viscoelasticity of Asphalt Mixtures.

Aggregate is an indispensable raw material for asphalt pavement construction. This study evaluates the influences of aggregate morphological characteristics on the high- and low-temperature viscoelasticity of asphalt mixtures. Based on simplex lattice mixture design (SLD), asphalt mix samples were designed and prepared with the same gradation but three different types of aggregates. Subsequently, three morphological characteristics of aggregate (roundness, perimeter index, and erosion-dilation area ratio) are presented to characterize fine and coarse aggregates. Then based on Burgers viscoelastic model, uniaxial compression static creep test was carried out to analyze the high-temperature viscoelastic properties for asphalt mortar and mixture. Meanwhile fitting Prony series models have been utilized to represent relaxation modulus conversed from creep compliance and the low-temperature relaxation characteristics can be also discussed. The experimental results indicated that morphological characteristics of aggregate, especially fine aggregates, are strongly correlated with the viscoelastic parameters of asphalt mixtures. However, the complex morphological characteristics of aggregates have opposite influences on the high- and low-temperature viscoelastic parameters. Therefore, when considering both high- and low-temperature viscoelastic properties, the aggregate proportion was optimized for the appropriate morphological characteristics, which will provide a reference for asphalt mixture design.

DUSST: Development of a new stress sweep fatigue test for asphalt mixtures

Fatigue cracking is one of the main damage mechanisms that take place in asphalt pavements. However, its evaluation during the design asphalt mixtures is not usually considered due to the complexity of the tests required, their high costs and the long time required to perform them. As a consequence, several research teams are working on developing new test procedures to reduce the time related to fatigue characterization of asphalt mixtures. In this context, this paper presents the development of a new test procedure consisting of a cyclic uniaxial tension-compression test in which the stress applied increases every 5000 cycles. In this manner, it is possible to evaluate a mixture’s response under cyclic loading at different stress levels in one test. Also, failure of the mixture takes place in a shorter time period than that required by classical time sweep fatigue tests. This paper presents results obtained in the application of this new methodology to a mixture frequently used in Chilean pavement structures (type IV-A-12 by Chilean standards) with three different asphalt binders: a conventional binder (CA-24), a high modulus binder (CA-HM) and a polymer-modified binder (CA-PM). We evaluated three different types of aggregates obtained through two different shredding processes. Results achieved in the development of our Direct Uniaxial Stress Sweep Test (DUSST) show that it is an experimental method with great potential. This test can characterize fatigue behaviors of asphalt mixtures in a shorter time by using important parameters such as initial strain, failure strain, complex modulus and dissipated energy. In addition, we obtained a good sensitivity of the DUSST main parameters to variables evaluated.

Analysis of Aggregate Morphological Characteristics for Viscoelastic Properties of Asphalt Mixes Using Simplex Lattice Design.

Morphological characteristics of aggregates have direct impacts on performances of asphalt mixes. This paper aims to investigate the effects of the morphological characteristics of fine and coarse aggregates on the high-temperature viscoelastic properties of asphalt mortars and mixtures. For this purpose, an experimental proportion scheme was designed for asphalt mixes prepared with three different types of aggregates (basalt, andesite and pebble/river sand) based on the simplex lattice design (SLD) method. Three morphological parameters were chosen to characterize shape, angularity and texture of aggregates. Afterwards, the uniaxial compression creep test was conducted for asphalt mixes and the high-temperature viscoelastic properties were obtained based on Burgers model. The effects of fine and coarse aggregates on the viscoelastic properties are analyzed through asphalt mortars and mixtures, respectively. The results showed that aggregate morphological characteristics correlate with the high-temperature viscoelastic properties of asphalt mixes, especially for fine aggregates. Aggregates with complex morphological characteristics are conducive to improving the deformation recovery and anti-deformation of asphalt mixes. Furthermore, coarse aggregates can enhance the anti-deformation of asphalt mixture effectively due to its skeleton effect.

Mechanical properties of alkali activated ground SiMn slag mortars with different types of aggregates

This research investigates the mechanical performance and dimensional stability of mortars whose binder is prepared by alkali activation of ground granulated SiMn slag. Two types of activators have been used: NaOH and waterglass solutions. Three different types of aggregates have been tested: silica sand, limestone sand, and recycled sand obtained from recycled concrete. Three activator concentrations have been adopted in the binder design: 3.0, 3.5 and 4.0% Na2O for NaOH solution; and 4.0, 4.5 and 5.0% Na2O for waterglass solutions with a constant SiO2/Na2O of 1.0. The best mechanical performance was obtained for an aggregate/slag ratio of 2/1 when silica sand was used as aggregate: 68 MPa were obtained when waterglass was used as activator, and %Na2O of 4.5–5.0% at 90 days; 54 MPa were obtained for NaOH as activator and 4.0% Na2O at 90 days. Limestone sand also offered a good mechanical performance although the maximum compressive strength achieved was about 25% lower than values obtained with silica sand, but recycled concrete aggregate mortars exhibited poor results, probably due to the high absorption of recycled aggregates. The higher shrinkage was registered in mortars activated with waterglass, although autogenous shrinkage was low for all types of activators and aggregates, except for recycled concrete aggregate.

A general database of hydrometeor single scattering properties at microwave and sub-millimetre wavelengths

Abstract. A main limitation today in simulations and inversions of microwave observations of ice hydrometeors (cloud ice, snow, hail, etc.) is the lack of data describing the interaction between electromagnetic waves and the particles. To improve the situation, the development of a comprehensive dataset of such scattering properties has been started. The database aims at giving a broad coverage in both frequency (1 to 886 GHz) and temperature (190 to 270 K), to support both passive and active current and planned measurements, and to provide data corresponding to the full Stokes vector. This first version of the database is restricted to totally random particle orientation. Data for 34 particle sets, i.e. habits, have been generated. About 17 of the habits can be classified as single crystals, three habits can be seen as heavily rimed particles, and the remaining habits are aggregates of different types, e.g. snow and hail. The particle sizes considered vary between the habits, but maximum diameters of 10 and 20 mm are typical values for the largest single crystal and aggregate particles, respectively, and the number of sizes per habit is at least 30. Particles containing liquid water are also inside the scope of the database, but this phase of water is so far only represented by a liquid sphere habit. The database is built upon the netCDF4 file format. Interfaces to browse, extract and convert data for selected radiative transfer models are provided in MATLAB and Python. The database and associated tools are publicly available from Zenodo (https://doi.org/10.5281/zenodo.1175572, Ekelund et al., 2018b), and https://doi.org/10.5281/zenodo.1175588, Mendrok et al., 2018, respectively). Planned extensions include non-spherical raindrops, melting particles and a second orientation case that can be denoted as azimuthally random.

Influence of Recycled Asphalt Pavement on Interfacial Energy and Bond Strength of Asphalt Binder for Different Types of Aggregates

The bond between aggregate and asphalt binder depends on many factors, such as chemistry of materials, nature of aggregates, and quality of asphalt binder. The present study evaluates the effects of recycled asphalt pavement (RAP) on the bonding behavior of asphalt binder for acidic (granite and quartzite) and basic (basalt and limestone) aggregates. AC30 binder was blended with different proportions of RAP binder (15%, 25%, and 40%). The interfacial energy and bond strength of 16 combinations (four asphalt binders × four aggregates) of aggregate-asphalt binder system were evaluated based on a surface free energy (SFE) approach and binder bond strength (BBS) test, respectively. One of the strong motivations of the present study was to evaluate how interfacial energy parameters calculated based on the SFE of an aggregate-asphalt binder system may correlate with the outcome obtained from a BBS test. The results showed that AC30 binder modified with RAP binder had a good performance for basic aggregates compared with acidic aggregates. Basic aggregates (limestone and basalt) showed cohesive failure before and after conditioning, indicating minimal effects of water on interfacial bond strength. However, acidic aggregates (granite and quartzite) showed cohesive failure in dry conditions and adhesive failure after wet conditioning, implying detrimental effects of water on interfacial bond strength for these aggregates. The failure pattern of aggregates in cohesion was supported by a reduction in cohesion energy of asphalt binder after the addition of RAP binder. Correlation between interfacial energy parameters (obtained from SFE) and BBS strength depends on aggregate types and failure patterns.