scholarly journals On Site Improvement of Fines-Rich Unbound Granular Materials with Hydrophobic Polymer and Lime

2021 ◽  
Vol 13 (23) ◽  
pp. 13479
Author(s):  
Cameron Hopkins ◽  
Donald Cameron ◽  
Md Mizanur Rahman
Keyword(s):  
Capillary Rise ◽  
Partial Replacement ◽  
Repeated Loading ◽  
High Plasticity ◽  
Carbon Footprints ◽  
Traffic Demand ◽  
Permanent Strain ◽  
Laboratory Characterization ◽  
Traffic Volumes

Many roads that were initially designed for relatively low traffic volumes need re-surfacing or partial replacement of the unbound granular material to satisfy current traffic demand. Significant research efforts based on laboratory studies have been seen in the literature to characterize the suitability of virgin materials, which is relatively expensive and unsustainable. Therefore, the object of this study is the in situ recycling of existing materials in two road sections by improving their properties with a suitable additive. A hydrophobic synthetic polymer was chosen for two trials due to the high plasticity of fines of the in situ materials and a high chance of water intrusion in the low-lying plains in Adelaide. The extensive laboratory characterization shows that hydrophobicity is imparted in capillary rise tests, improved drainage in permeability tests, and greater matric suction at the same moisture content. Furthermore, the unconfined compressive strength was increased. The repeated loading triaxial testing showed higher stiffness and lowered permanent strain to withstand higher traffic volume. In general, in situ recycling is adaptable and considered to be cheaper and sustainable. The estimated current costs and carbon footprints are presented for re-construction and in situ recycling with dry powder polymer, or solely with lime, to help construction planning.

Mitigation of permanent deformation in base layer containing recycled asphalt aggregates

2013 ◽  
Vol 40 (2) ◽  
pp. 181-187 ◽  
Author(s):  
Jean-Pascal Bilodeau ◽  
Guy Doré ◽  
Jonas Depatie
Keyword(s):  
Asphalt Concrete ◽  
Deformation Behaviour ◽  
Permanent Deformation ◽  
Design Procedure ◽  
Base Layer ◽  
Repeated Loading ◽  
Recycled Asphalt ◽  
Thickness Increase ◽  
Permanent Strain ◽  
Pavement Base

The use of recycled asphalt pavement (RAP) aggregates as replacement for new materials in the pavement base weakens the layer in regards to the resistance to permanent deformation under repeated loading. A mechanistic based design procedure is proposed to ensure that base layers containing RAP particles have a similar rutting behaviour to base layers made of virgin aggregates. The design procedure allows calculating an asphalt concrete thickness increase that is based on permanent deformation behaviour of base materials. The calculation approach is based on multistage triaxial permanent deformation tests performed on granular material samples with varied RAP content. The tests allowed proposing an equation that relates permanent strain rate, RAP content, and deviatoric stress, which is the basis of the design procedure. Design charts are proposed to select adequate thickness increase for the asphalt concrete layer according to the expected RAP content in the base layer and asphalt concrete modulus.

scholarly journals Efficacy of Natural Zeolite and Metakaolin as Partial Alternatives to Cement in Fresh and Hardened High Strength Concrete

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Iswarya Gowram ◽  
Beulah M ◽  
MR Sudhir ◽  
Mothi Krishna Mohan ◽  
Deekshith Jain
Keyword(s):  
High Strength Concrete ◽  
Natural Zeolite ◽  
Environmental Concern ◽  
Concrete Strength ◽  
High Strength ◽  
Cementitious Materials ◽  
Partial Replacement ◽  
Split Tensile Strength ◽  
Carbon Footprints ◽  
Strength Concrete

Urbanization and industrialization have dramatically increased the manufacture of cement causing substantial pollution of the environment. The primary global concern related to cement manufacture has been the management of the large carbon footprints. The usages of environmentally friendly cementitious materials in the construction of structures have proved to be a viable option to deal with this environmental concern. Therefore, it is necessary to further explore the usage of cementitious materials which can replace cement albeit partially. In this direction of research, two such cementitious materials, namely, natural zeolite and metakaolin have been investigated in this study. High-strength concrete M60 with natural zeolite and metakaolin as the partial replacements for the cement has been prepared in this work. Polycarboxylic ether-based superplasticizer solution has been used to enhance workability. The test specimen cast and cured for 3, 7, 28, 60, and 90 days at ambient room temperature has been tested for compressive strength, split tensile strength, and flexural strength as per the Indian standards. The optimum mix of high-strength concrete thus manufactured has met the Indian standards, and the combination of cement +5% natural zeolite +10% metakaolin has exhibited the highest compressive, split tensile, and flexural strengths at 90 days of curing. Natural zeolite and metakaolin when used in smaller proportions have increased the concrete strength, and these materials are recommended for partial replacement of cement.

scholarly journals Adipose-Derived Mesenchymal Stromal/Stem Cells: Tissue Localization, Characterization, and Heterogeneity

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Patrick C. Baer ◽  
Helmut Geiger
Keyword(s):  
Stem Cells ◽  
Adipose Tissue ◽  
Stem Cell ◽  
Cultured Cells ◽  
Current Knowledge ◽  
High Plasticity ◽  
Culture Methods ◽  
Tissue Localization ◽  
Stromal Stem Cells

Adipose tissue as a stem cell source is ubiquitously available and has several advantages compared to other sources. It is easily accessible in large quantities with minimal invasive harvesting procedure, and isolation of adipose-derived mesenchymal stromal/stem cells (ASCs) yields a high amount of stem cells, which is essential for stem-cell-based therapies and tissue engineering. Several studies have provided evidence that ASCs in situ reside in a perivascular niche, whereas the exact localization of ASCs in native adipose tissue is still under debate. ASCs are isolated by their capacity to adhere to plastic. Nevertheless, recent isolation and culture techniques lack standardization. Cultured cells are characterized by their expression of characteristic markers and their capacity to differentiate into cells from meso-, ecto-, and entodermal lineages. ASCs possess a high plasticity and differentiate into various cell types, including adipocytes, osteoblasts, chondrocytes, myocytes, hepatocytes, neural cells, and endothelial and epithelial cells. Nevertheless, recent studies suggest that ASCs are a heterogeneous mixture of cells containing subpopulations of stem and more committed progenitor cells. This paper summarizes and discusses the current knowledge of the tissue localization of ASCs in situ, their characterization and heterogeneityin vitro, and the lack of standardization in isolation and culture methods.

Evaluating the Operational Efficiency of Two Versions of Super Diverging Diamond Interchange Design: A Case Study in Denver, Colorado

2021 ◽  
pp. 036119812110372
Author(s):  
Muhammad Tahmidul Haq ◽  
Amirarsalan Mehrara Molan ◽  
Khaled Ksaibati
Keyword(s):  
Research Effort ◽  
Traffic Signals ◽  
Operational Efficiency ◽  
Traffic Demand ◽  
Operational Analysis ◽  
Signal Coordination ◽  
Traffic Volumes ◽  
Microsimulation Models ◽  
Better Than

This paper aims to advance the current research on the new super diverging diamond interchange (super DDI) design by evaluating the operational efficiency using real-world locations. As part of a comprehensive research effort on improving the performance of failing service interchanges in the mountain-plains region, the study identified three interchanges (Interstate 225 and Mississippi Avenue, Interstate 25 and 120th Avenue, and Interstate 25 and Hampden Avenue) at Denver, Colorado as the potential candidates to model for future retrofit. Four interchange designs (i.e., existing CDI [conventional diamond interchange], DDI, super DDI-1, and super DDI-2) were tested in this study. The operational analysis was conducted using VISSIM and Synchro. Several microsimulation models (120 scenarios with 600 runs in total) were created with three peak hours (a.m., noon, and p.m.) for existing (the year 2020) and projected (the year 2030) traffic volumes. The study considered two simulation networks: (1) when no adjacent traffic signal exists, to determine how the four interchange designs would perform if there were no adjacent signals or they were far away from the interchange; and (2) when there are two adjacent traffic signals, to evaluate the performance of the four interchanges in a bigger corridor with signal coordination needed. An important finding is that super DDI designs outperformed DDI with adjacent signals and higher traffic demand, while DDI performed similarly to or sometimes insignificantly better than super DDI if no adjacent intersections were located in the vicinity and if the demand was lower than the DDI’s capacity.

Large plasticity in magnesium mediated by pyramidal dislocations

Science ◽  
2019 ◽  
Vol 365 (6448) ◽  
pp. 73-75 ◽  
Author(s):  
Bo-Yu Liu ◽  
Fei Liu ◽  
Nan Yang ◽  
Xiao-Bo Zhai ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Electron Microscope ◽  
Plastic Strain ◽  
Crystal Size ◽  
High Stress ◽  
High Strength ◽  
High Plasticity ◽  
Transmission Electron ◽  
Small Crystal Size

Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for widespread applications is the limited ductility of magnesium, which has been attributed to 〈c+a〉 dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that 〈c+a〉 dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more 〈c+a〉 dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.

scholarly journals Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

2017 ◽  
Author(s):  
Yuan You ◽  
Ralf M. Staebler ◽  
Samar G. Moussa ◽  
Yushan Su ◽  
Tony Munoz ◽  
...  
Keyword(s):  
Dispersion Model ◽  
Urban Air Pollution ◽  
Forecast Model ◽  
Emission Factors ◽  
Ammonia Nitrogen ◽  
Traffic Emissions ◽  
Mixing Ratios ◽  
Air Quality Forecast ◽  
Traffic Volumes

Abstract. Traffic emissions contribute significantly to urban air pollution. Measurements were conducted over Highway 401 in Toronto, Canada, with a long-path Fourier Transform Infra-Red Spectrometer (FTIR) combined with a suite of micrometeorological instruments, to identify and quantify a range of air pollutants. Results were compared with simultaneous in-situ observations at a roadside monitoring station, and with output from a special version of the operational Canadian air quality forecast model (GEM-MACH). Elevated mixing ratios of ammonia (0–23 ppb) were observed, of which 76 % were associated with traffic emissions. Hydrogen cyanide was identified at mixing ratios between 0 and 4 ppb. Using a simple dispersion model, an integrated emission factor of on average 2.6 g km−1 carbon monoxide was calculated for this defined section of Highway 401, which agreed well with estimates based on vehicular emission factors and observed traffic volumes. Based on the same dispersion calculations, vehicular average emission factors of 0.04, 0.36 and 0.15 g km−1 were calculated for ammonia, nitrogen oxide, and methanol respectively.

scholarly journals Influence of Hydrated Lime on the Properties and Permanent Deformation of the Asphalt Concrete Layers in Pavement

2015 ◽  
Vol 4 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Ahmed F. Al-Tameemi ◽  
Yu Wang ◽  
Amjad Albayati
Keyword(s):  
Asphalt Concrete ◽  
Raw Materials ◽  
Permanent Deformation ◽  
Fatigue Cracking ◽  
Hydrated Lime ◽  
Concrete Pavement ◽  
Partial Replacement ◽  
Repeated Loading ◽  
Concrete Mixtures ◽  
Asphalt Concrete Pavement

Abstract Flexible or asphalt concrete pavement is the paving system most widely adopted all over the world. It has been recognized that there are many different types of the factors affecting the performance and durability of asphalt concrete pavement, including the service conditions, such as: the variation of temperature from mild to extremes and the repeated excessive axle loading as well as the inadequate quality of the raw materials. All of these when combined together are going to accelerate the occurrence of distresses in flexible pavement such as permanent deformation and fatigue cracking. As the result, there has an urgent need to enhance the ability of asphalt concrete mixture to resist distresses happened in pavement. Use of additives is one of the techniques adopted to improve pavement properties. It has been found that hydrated lime might be one of the effective additives because it is widely available and relatively cheap compared to other modifiers like polymers. This paper presents an experimental study of the hydrated-lime modified asphalt concrete mixtures. Five different percentages of the hydrated lime additive were investigated, namely (1, 1.5, 2, 2.5 and 3 percent). The hydrated lime additive was used as partial replacement of limestone filler by total weight of the aggregate. The designed Hot Mix Asphalt (HMA) concretes are for the application of three pavement courses, i.e. Surface, Leveling and Base. These mixtures are designed and tested following Marshall procedure and uniaxial repeated loading to evaluate permanent deformation at different temperatures of 20°C, 40°C and 60°C. The experimental results show that the addition of hydrated lime as a partial replacement of ordinary limestone mineral filler results a significant improvement on mechanical properties and the resistant to permanent deformation of the designed asphalt concrete mixtures.

New constraints on metamorphism in the Highjump Archipelago, East Antarctica

2016 ◽  
Vol 28 (6) ◽  
pp. 487-503 ◽  
Author(s):  
Naomi M. Tucker ◽  
Martin Hand
Keyword(s):  
Granulite Facies ◽  
East Antarctica ◽  
Partial Replacement ◽  
Granulite Facies Metamorphism ◽  
Metasedimentary Rocks ◽  
Facies Metamorphism ◽  
Antarctic Expedition ◽  
Higher Temperature ◽  
Temperature And Pressure

AbstractThe age and conditions of metamorphism in the Highjump Archipelago, East Antarctica, are investigated using samples collected during the 1986 Australian Antarctic expedition to the Bunger Hills–Denman Glacier region. In situ U-Pb dating of monazite from three metasedimentary rocks yields ages between c. 1240–1150 Ma and a weighted mean 207Pb/206Pb age of 1183±8 Ma, consistent with previous constraints on the timing of metamorphism in this region and Stage 2 of the Albany–Fraser Orogeny in south-western Australia. This age is interpreted to date the development of garnet ± sillimanite ± rutile-bearing assemblages that formed at c. 850–950°C and 6–9 kbar. Peak granulite facies metamorphism was followed by decompression, evidenced largely by the partial replacement of garnet by cordierite. These new pressure–temperature determinations suggest that the Highjump Archipelago attained slightly higher temperature and pressure conditions than previously proposed and that the rocks probably experienced a clockwise pressure–temperature evolution.

Preventing surface deposition of chromium with asphalt caps at chromite ore processing residue sites: a case study

2007 ◽  
Vol 44 (7) ◽  
pp. 814-839 ◽  
Author(s):  
Karen S Henry ◽  
John C Petura ◽  
Steven Brooks ◽  
Steven Dentico ◽  
Stephen A Kessel ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Capillary Rise ◽  
Matric Suction ◽  
Upward Movement ◽  
Chromite Ore Processing Residue ◽  
Chromite Ore ◽  
Ore Processing ◽  
Unsaturated Hydraulic Conductivity ◽  
Water Rise

Caps were constructed on chromite ore processing residue (COPR) sites in the Kearny, New Jersey, area between 1989 and 1994 to prevent human exposure to hexavalent chromium (Cr(VI)). The caps comprise geotextile overlain by 100 mm of dense graded aggregate (DGA) and 100 mm of hot mix asphalt (HMA). Prior to constructing these "composite asphalt caps" (CACs), Cr(VI) was sometimes deposited on surface soils as chromate (salts) during evaporative periods. We initially thought the geotextile and DGA acted as a capillary barrier, stopping capillary water rise, but site inspection revealed that the DGA and geotextile were too moist to perform this function. Further study included a literature review, DGA capillary rise estimates, in situ measurement of soil-water content over 7 months at a representative COPR site, and numerical modeling of matric suction gradients induced by evaporation. The collective results reveal that the CACs eliminate upward matric suction gradients from the COPR–soil through the DGA, thereby precluding surface chromate deposition. Even during evaporative periods, the low unsaturated hydraulic conductivity of the HMA restricts upward movement of moisture and soluble chromate from underlying COPR–soil. In contrast, there are almost always upward matric suction gradients in uncapped COPR–soil.Key words: capillary rise, chromite ore processing residue, chromate, hexavalent chromium, composite asphalt cap, evaporation.

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