Hot Mix Research Articles

A comparative study for improving the mechanical properties of cold bituminous emulsion mixtures with cement and waste materials

This paper reports the experimental test results of a research project aimed at developing a new cold bituminous emulsion mixtures (CBEM’s) containing fly ash from incinerated domestic and industrial by-products compared with those results of traditional control cold containing OPC and hot mix asphalt.The main objectives of the experiments were to investigate the improvement in mechanical properties of CBEM’s due to incorporating OPC, and detect the possibility of replacing the OPC with waste fly ash materials. The mixtures mechanical properties investigated were; ITSM, creep stiffness. Durability in term of water sensitivity was investigated too.The results have shown comparative mechanical properties of CBEM’s to HMA. Furthermore, the new CBEM’s with fly ash used as a replacement of filler achieved outstanding results compared with traditional CBEM with and without addition of OPC. Therefore, this paper introduces a new CBEM’s having outstanding mechanical characteristics, cost effective, and environmental friendly.

Characterization of biodegradable poly(butylene adipate-co-terephtalate)/sodium caseinate films loaded with an alkyl furanoside as antimicrobial agent

A biodegradable material was prepared by blending sodium caseinate (NaCAS) with poly(butylene adipate--terephtalate) (PBAT). The best composition was selected from mechanical testing of PBAT/NaCAS blends for further manufacture of a partially biobased film able to deliver a bioactive compound. From stress-strain testing, it was determined that the best mechanical properties while keeping maximum NaCAS content were obtained for 80/20 w/w PBAT/NaCAS blends plasticized with 10 % Glycerol (Gly). The surfactant octyl-beta--galactofuranoside was used as an antitubercular agent and directly incorporated in the blend during hot mixing. The biodegradable films containing 1-5 % by weight of galactofuranoside were observed by SEM and showed crystalline structures on their surface. From X-ray diffraction studies, it was demonstrated that on the surface, the octyl galactofuranoside crystallized orthorhombic with space group P2(1)2(1)2(1). The molecular packing calculated from X-ray data showed bilayer structures with interdigitated octyl chains. Finally, the mycobacteriostatic properties of Gly-plasticized PBAT/NaCAS films were evaluated from a modified Kirby-Bauer test.

Zn, Fe and S isotope fractionation in a large hydrothermal system

The genesis of hydrothermal ore deposits is of crucial economic importance. This study investigates the extent, causes and consequences of zinc and iron isotope fractionation in a large hydrothermal system at the world-class Navan Zn–Pb orebody, Ireland. Large variations in Zn, Fe and S isotope compositions have been measured in microdrilled sphalerite (ZnS) at the millimetre scale. δ66Zn and δ56Fe display a well-defined positive correlation and both also correlate with δ34S. These relationships represent the combined effects of kinetic Zn and Fe isotope fractionation during sphalerite precipitation, and S isotope variation through mixing of hot, metal-rich hydrothermal fluids and cool, bacteriogenic sulfide-bearing brines. Combined with S isotope data, δ56Fe and δ66Zn data on mine concentrates confirm that hydrothermal sulfide is a minor component of the overall deposit signature. Our data suggest that incoming pulses of metal-rich hydrothermal fluid triggered sulfide mineralisation, and that rapid precipitation of sphalerite from hydrothermal fluids will lead to strong kinetic fractionation of Zn and Fe isotopes at very short time and length scales, thereby limiting the use of Fe and Zn isotopes as exploration tools within deposits, but revealing the possibility of detecting new deposits from isotopically heavy Zn–Fe geochemical halos.

Root Cause Analysis of Failure in Hot and Cold Mixing Point in Hydrogen Generation Unit (HGU) due to Thermal Fatigue Phenonmenon

Root Cause Analysis of Failure in Hot and Cold Mixing Point in Hydrogen Generation Unit (HGU) due to Thermal Fatigue Phenonmenon

Mechanical properties of hot bituminous mixes manufactured with recycled aggregate of Silestone® waste

This article presents the results of a research project which analyzes the viability of incorporating waste material from decorative quartz solid surfacing in the manufacture of hot bituminous mixes. For this purpose, various bituminous mixes were manufactured with waste aggregate in different percentage. A set of tests were carried out that permitted the characterization of the mechanical behavior of these mixes. The results of these tests were similar to the results obtained when conventional mixes made from virgin quarry aggregate were tested. The results for moisture sensitivity as well as for wheel track rutting on mixes showed the optimal performance of this waste material even under very demanding traffic conditions. Laboratory studies showed that the use of this waste material in the manufacture of bituminous mixes is technically viable and can provide high-quality recycled aggregates at a very low cost, which can be used in the pavement of road.

Influence of Peanut oil on the Flow Characteristics of Cowpea Slurry

Hot mix cowpea slurries at 30% cowpea solids and various concentrations of peanut oil were prepared by mixing measured amounts of cowpea flour with adequate amounts of oil and hot waterat 70 oC. Slurries were held with intermittent agitation in a water bath maintained at 70 oC for 15 minutes before shearing in a viscometer at 20 oC. Similarly, cold-mix slurries produced with cold tap water for formulation and a subsequent holding regime for 3 hours with intermittent agitation under room temperature (20 oC –25 oC )were also sheared at 20 oC. The shear responses adequately fitted the power law equation and exhibited very low levels of yield stress. Theadded oil was completely absorbed in the hot-mix slurries at levels of 1 – 11% fat covered in the study. Increase in fat concentration increased the consistency coefficient for the hot-mix slurries only without any corresponding influence in the cold mix slurries. While the consistencycoefficient exhibited a linear dependence on fat concentration, the flow behaviour index remained unaltered for the hot-mix slurries. Generally, the apparent viscosity (at 10 S-1) showed a 2.5% increase for each % increase in fat concentration.

Moisture damage potential of cold asphalt

This paper presents a study of the effects of moisture ingress on the mechanical properties of a cold-laid grave emulsion asphalt mixture. A vacuum moisture saturation technique has been developed to induce different moisture levels in laboratory-prepared specimens, which simulate site conditions deduced from a field trial. For comparison purposes, a hot mix with the same aggregates and base binder was also used in the study. The stiffness of both materials was monitored under different curing conditions for an extended duration. Semi-circular specimens loaded in a three-point bending test were used to determine fracture properties: fracture toughness and fracture energy. Results showed that, although the hot mixture had good fracture properties, the cold mixture's results were only marginally lower. The vacuum saturation treatment led to enhanced yield performance at low temperatures of both mixtures in the fracture test. The high level of moisture treatment given to the cold mixture made it behave like the hot asphalt mixture at low temperatures.

Features of new developments in the field of basic refractories

New developments are described from OOO Gruppa Magnezit and OAO Kombinat Magnezit concerning basic refractories, i.e. fluxes, starting mixes, hot repair mixes, backup materials, mortars, etc. A combined scheme for producing new forms of refractory materials, and also their physicochemical and operating properties are provided.

Forensic Investigations of Roadway Pavement Failures

This paper presents three field projects to illustrate the integrated approach to forensic investigations of roadway pavement failures used widely in Texas. In each case, the combined ground-penetrating radar (GPR) and falling weight deflectometer (FWD) data were extremely useful for identifying contributing factors, such as stripping in the hot mix or localized areas of wet or weak base. Dynamic cone penetration (DCP) is used for validating problems with base and subbase layers. Laboratory tests are often required to complete the investigation, especially if the repair strategy calls for in-place recycling of the existing structure. The extent of stripping and high porosity that caused delamination for Projects 1 and 2 was detected by GPR and verified by core samples. GPR, FWD, DCP, and field soil samples all showed indications that the existing base on Project 1 was wet and the stiffness was only about one-third that of a typical flexible base in Texas. FWD data demonstrate that the pavement structures for Projects 1 and 2 were inadequate, so a rehabilitation strategy was selected that included structural strengthening. In Project 3, GPR, lab density, and permeability tests indicate that the dramatic pavement failures were attributable to moisture entering the base through a poorly compacted asphalt concrete layer and poor longitudinal joints. The base material was found to be highly susceptible to moisture and did not meet the Texas Department of Transportation’s compressive strength requirements when subjected to capillary soaking. The repetitive triaxial test results revealed that the stiffness and load-carrying capability became inadequate when the base materials were exposed to moisture. The pavement structure had been totally replaced in 2004.

Impact of Extremely Hot Weather and Mixing Method on Changes in Properties of Ready Mixed Concrete during Delivery

Riyadh is located in central Saudi Arabia. Its extremely hot, dry environment was used to investigate concrete compressive strength, slump, and temperature changes during ready mixed concrete (RMC) delivery. Representing three plants employing a truck-mixing method and three plants employing a central-mixing method in their operations, testing was performed using a total of 80 delivery trucks. Differences in RMC property changes that were not significant were indicated by study results during delivery in both Riyadh's extremely hot, dry summertime environmental conditions and the midwestern United States' much milder summer conditions. The study showed that during summertime delivery, concrete slump lost 37% of its initial value and concrete temperature increased by an average of 1.1 degrees Celsius (2.0 degrees Fahrenheit). There was a slightly higher compressive strength at the site than at the plant. Long travel times did not significantly affect compressive strength. Effective control of adverse hot weather effects on concrete production and delivery, even under the region's extremely hot prevailing weather conditions, was shown possible by controlling concrete temperature, avoiding delivery during noon hours, and using water-reducing and retarding admixtures, per ACI 305R recommendations. In this study, there was no observation of the anticipated increased slump loss rate problem associated with hot weather use of water-reducing and retarding admixtures.

Investigations of Mixing Zones subject to Thermal Fatigue

Further the through wall crack in an elbow of the Residual Heat Removal (RHR) system of Civaux 1 in 1998, a large investigation program has been completed on removed parts of pipes to better assess the factors responsible for thermal fatigue cracking in pipe components where hot and cold fluids mix together. This article presents the results of destructive investigations performed on numerous parts of the RHR system of EDF plants, on a nozzle of the primary system and on a nozzle of the secondary system and their contribution to understanding and assessing harmfulness of the phenomenon.The damage concerns only certain RHR mixing zones: the mixing tee at intersection between downstream the exchanger and the by-pass line and the mixing tee at location of intersection of two portions of minimum flow line. Deep cracks are always associated with high temperature differences and long times of operation. The deepest cracks are always located close to the welds, in areas showing geometrical singularities and minimal thickness. Crack networks in running parts concern only the very first millimeters of the inner wall.Other mixing zones have been investigated: destructive examinations of a charging line primary nozzle of the Chemical and Volume Control System (CVCS), of two tees between the main line and the minimum flow line of the RHR system and of one tee connecting the Feed Flow Control System (FFCS) to the Auxiliary Feedwater System (AFS) did not show any thermal fatigue crack.EDF has developed a method for identification of fluid mixing zones subject to thermal fatigue damage. This method is based on the assessment of a usage factor, using the knowledge acquired during a large R&D program. This program investigated the thermal loadings in mixing tees acquired through several thermohydraulic mockup tests and the austenitic steel behavior under high cycle thermo-mechanical loadings.The results of the destructive examinations have been used to strengthen the identification methodology of mixing zones potentially affected by thermal fatigue. Damage found in the destructive examinations are always correlated with usage factors a lot greater than 1.The methodology has been applied to all mixing zones of safety related circuits of plants operated by EDF. It has lead to identify the ones with a usage factor greater than unity and to an appropriate in-service inspection program based on volumic non-destructive examinations.

Identification of lime plaster in prehistory using petrographic methods: A review and reconsideration of the data on the basis of experimental and case studies

AbstractMost prehistoric plasters and mortars consist of very small amounts of burnt lime mixed with anthropogenic debris, soil, and sediment. To solve the problem of identification of such small amounts of lime in impure lime plasters, a series of experimental plasters were prepared and studied with petrographic methods. Samples of living floors from five prehistoric sites in Greece were also reanalyzed under the light of the experimental findings and compared with natural calcareous sediment. The most promising features for identifying lime are transitional textures of partially carbonized slaked lime that can be observed in the lime lumps and the binding matrix. They are usually in the form of ill‐crystallized portlandite and calcite mixtures or cryptocrystalline calcite. Well‐reacted calcitic groundmass, shrinkage fractures, and occasionally colloidal forms are also additional indications. The present experimental study shows that lime could be easily produced by heating porous, soft calcareous materials. This would probably account for the very frequent use (in small quantities) of lime in Greek prehistory. Plaster and mortars were made by mixing damp anthopogenic dirt as aggregate and fragments of quicklime, a technique known as “hot mixing.” © 2007 Wiley Periodicals, Inc.

Application of Ultraviolet Spectrophotometry to Estimate Occupational Exposure to Airborne Polyaromatic Compounds in Asphalt Pavers

An ultraviolet (UV) spectrophotometric procedure was devised for the determination of polycyclic aromatic compound-oriented organic soluble matter in vapors and particulate collected from emissions of hot asphalt mix. Ultrasonic extraction was carried out with acetonitrile, followed by UV measurements at 254 nm. Polycyclic aromatic compounds (PACs) in volatile and particulate fraction were quantified as phenanthrene or benzo[k]fluoranthene equivalents. A comparison between UV and high-pressure liquid chromatography with fluorescence detection showed that PACs were one to three orders of magnitude higher than the sum of 15 priority polycyclic aromatic hydrocarbons (PAHs); still, significant correlations were found between volatile or particulate PACs and, respectively, total volatile or particulate PAHs. Moreover, in the particulate phase, PACs correlated with total particulate matter quantified by gravimetry. The proposed procedure was employed in a field study for monitoring personal exposure to asphalt emissions of workers engaged in road construction. Observed levels of acetonitrile-soluble PACs in air samples were very low (2–20 μg/m 3 ); however, asphalt pavers were exposed to significantly higher concentrations of volatile PACs than construction workers (geometric mean, 5.9 μg/m 3 vs. 4.1 μg/m 3 ). This method for estimating the global content of volatile or particulate PACs in air samples satisfies our requirements of simplicity and is suitable for conducting an initial screening to assess exposure to airborne polyaromatic organics in asphalt pavers.

Urinary hydroxylated metabolites of polycyclic aromatic hydrocarbons as biomarkers of exposure in asphalt workers

Background. Fumes and vapours released during laying of hot asphalt mix have been recognised as a major source of exposure for asphalt workers. Objectives. We investigated the relationships between inhalation exposure to asphalt emissions and urinary biomarkers of polycyclic aromatic hydrocarbons (PAHs) in asphalt workers (AW, n=75) and in ground construction workers (CW, n=37). Methods. Total polyaromatic compounds (PAC) and 15 priority PAHs in inhaled air were measured by personal sampling. Hydroxylated PAH metabolites (OH-PAHs) (2-naphthol, 2-hydroxyfluorene, 3-hydroxyphenanthrene, 1-hydroxypyrene, 6-hydroxychrysene and 3-hydroxybenzo[a]pyrene) were determined in urine spot samples collected in three different times during the work week. Results. Median vapour-phase PAC (5.5 µg m–3), PAHs (≤50 ng m–3) and OH-PAHs (0.08–1.11 µg l–1) were significantly higher in AW than in CW, except in the cases of air naphthalene and 2-naphthol. Airborne levels of particle-phase contaminants were similar in the two groups and much lower than vapour-phase levels; metabolites of particulate PAHs were never found in quantifiable amounts. An appreciable increase in OH-PAH levels during the work day and work week was found in AW; median levels for 2-hydroxyfluorene, 3-hydroxyphenanthrene and 1-hydroxypyrene were, respectively, 0.29, 0.08 and 0.18 at baseline; 0.50, 0.18 and 0.29, pre-shift; 1.11, 0.44 and 0.44 µg l–1, post-shift. Each OH-PAH exhibited a characteristic profile of increase, reflecting differences in half-lives of the parent compounds. In non-smoking subjects, positive correlations were found between vapour-phase PAC or PAHs and OH-PAHs both in pre- and post-shift samples (0.34 ≤ r≤69). Smokers exhibited 2–5-fold higher OH-PAHs than non-smokers, at any time and at both workplaces. Conclusions. Our results suggest that OH-PAHs are useful biomarkers for monitoring exposure to asphalt emissions. The work-related exposure to PAC and PAHs was low in all AW, but urinary metabolites reflected exposure satisfactorily.

Disorder and dissolution enhancement: Deposition of ibuprofen on to insoluble polymers

Microcrystalline cellulose (MCC) and cross-linked polyvinylpyrrolidone (PVP-CL) were examined as polymeric carriers to support amorphous ibuprofen (IB). Drug/carrier systems were prepared as physical mixes, and drug was loaded onto the polymers by hot mix and solvent deposition methods. The systems were examined using differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD) and by dissolution testing. PVP-CL reduced drug crystallinity more than MCC and, surprisingly, even very simple mixing of ibuprofen with PVP-CL induced disordering of the drug. Increased ibuprofen dissolution rates were achieved with both polymers, in the order of solvent deposition > hot mixes > physical mixes. The increased dissolution rates could be attributed to a combination of faster dissolution from amorphous ibuprofen, microcrystalline drug deposition on carrier surfaces and polymer swelling. However, no clear relationship was observed between ibuprofen dissolution rates (using first order, Higuchi or Hixson–Crowell relationships) and drug crystallinity.

Substitution of Fly Ash, Slag, and Chemical Admixtures in Concrete Mix Designs

The Florida Department of Transportation (FDOT) requires contractors for FDOT’s projects to submit a proposed concrete mix design prior to the production of any concrete. The contractor must use mix designs approved by FDOT. Substitutions of ingredients other than coarse aggregate must be justified through trial mixtures, and authorized in writing by FDOT engineers. The study reported herein investigated whether substitutions of fly ash, slag, air-entraining admixtures, and Types A, D, and G admixtures could be performed and be allowed in FDOT approved concrete mix designs. Substitutions of the ingredients were performed on two typical FDOT hot weather mix designs in this study. The concrete properties considered were slump, air content, and compressive strength. Test data for substitution mix designs were compared with the data for the original mix design. Results show that the substitutions cause variability in concrete properties for both the fly ash and the slag mix designs. Statistically reliable con...

Construction-Related Temperature Differentials in Asphalt Concrete Pavement: Identification and Assessment

Numerous Washington State Department of Transportation (WSDOT) paving projects have experienced a cyclic occurrence of premature failure of open-textured asphalt concrete (AC) pavement sections by fatigue cracking, raveling, or both, generally called “cyclic segregation” or “endof-load segregation.” This resulted in an initial study in which mat temperature differentials were observed during laydown. In turn, this led to the current study and the reported results. Pavement temperature differentials result from placement of a cooler portion of the hot-mix mass into the mat. This cooler mass generally constitutes the crust, which can develop during hot-mix transport from the mixing plant to the job site. Placement of this cooler hot mix can create pavement areas near cessation temperature that tend to resist proper compaction (they may also exhibit tearing or roughness or appear to be open textured). These areas were observed to have decreased densities and a higher percentage of air voids (higher air voids). Four 1998 WSDOT paving projects were examined to determine the existence and extent of mat temperature differentials and associated material characteristics. An infrared camera was used to identify cooler portions of the mat, which were then sampled along with normal-temperature pavement sections. Gradation and asphalt content analysis showed no significant aggregate segregation within the cooler areas. However, these cooler portions of the mat consistently showed higher air voids than the surrounding pavement. On the basis of numerous studies that have related AC deterioration and high air voids in a mix, it is known that the areas of a mat with higher air voids may experience premature failure compared with the time to failure of the mat as a whole.

Structure of Lean Turbulent Partially-Premixed Flames Stabilized in a Co-Axial Jet Flame Burner

Lean premixed flames at very low equivalence ratios and high mean flow velocities can besustained in a co-axial jet flame burner. The flame shape involves a thin, highly turbulent flame region where most of the lean combustion occurs, and a base flame region which burns at the initial equivalence ratio. Due to the entrainment velocity induced by the high-speed inner jet flow, the flame also has a thin "pinched" region near the flame base. The entrainment of the hot product gas and mixing with the reactant, leading to preheating, along with the fact that the turbulence intensity increases gradually in the presence of the inner jet, are believed to be contributing factors in the stabilization of the flames in the current burner geometry. Addition of the inner jet of always lowers the overall equivalence ratio and enhances the stability limits. The minimum overall equivalence ratio achieved is 0.56 with a mean velocity of 60 m/s for the inner jet. This capability to generate lean premixed flames at high turbulence intensities and mean flow velocities is expected to have useful practical applications. Temperature measurements have been obtained using a point Rayleigh scattering technique, and the temperature profiles show a significant reduction in the flame temperature as the overall equivalence ratio is reduced using the inner jet air. The temperature pdf's show a shift of the cold reactant temperature to a higher value, indicating preheating of the reactant due to the entrainment of hot product gas that surrounds the lean flame. Also, there can be significant departure from flamelet behavior, associated with a bimodal temperature pdf, when the inner jet velocity becomes high. The temperature pdf's are no longer bi-modal at high turbulence intensities caused by the strong inner jet, with temperature pdf's showing a broadened temperature range in the flame zone.

Highly Ionized Interstellar Atoms—Heated, Cooled, or Mixed?

Recent observations with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, combined with Copernicus results, make possible a comparison between C+3 and O+5 interstellar column densities in both the halo and the disk of our Galaxy. The ratio N(C+3)/N(O+5) for six lines of sight in the disk is about an order of magnitude less than for five corresponding values in the halo. In the disk, the values of this ratio are in good general agreement with a variety of different models for conductive heating at an interface between hot and cool gas. As a working hypothesis we assume that this process is the dominant one for producing the observed highly ionized species in the disk. The much larger ratios for the halo lie between the ranges predicted by two different idealized models?radiative cooling of hot infalling gas and turbulent mixing of hot gas with the cool clouds past which it flows. Since both these processes should occur when hot gas flows past H I clouds in the halo, we assume tentatively that these two processes may be jointly responsible for much of the observed high ionization of halo atoms.

海底熱水系から供給される極微細粒子と海水との反応

Fe oxyhydroxide particles are formed by mixing of hot, H2S-rich, oxygen-poor, low-pH hydrothermal vent fluid with cold, oxygen-rich seawater in the hydrothermal plumes associated with seafloor hydrothermal systems. These Feoxyhydroxide particles derive their compositions from scavenging of dissolved constituents (e.g. PO4-3 V, As, rare earth elements, Th) from seawater during transport away from the vents. The scavenging processes of Fe oxyhydroxide playan important role in balancing the oceanic geochemical budgets of most rare earth elements and oxyanion species in seawater. The estimated scavenging rates are 6×1010 to 1.1×1011 tmol/year for P, 4.3×108 to 1.2×109 mol/year for V and 1.8×108 to 1.2×109 mob/year for As. These Fe oxyhydroxide particles are actively produced at the superfast-spreading (15cm/year) East Pacific Rise (EPR). During the RN Melville cruise, Fe-enriched hydrothermal plumes (Fe<730nm/l) were observed at S13°K50' to S17°00' of the East Pacific Rise (EPR). Fe-enriched plumes are dominated by Fe oxyhydroxide particles scavenging Si, P, and Ca from seawater. Room temperature Mossbauer spectra and FT-IR spectra of these Fe oxyhydroxide particles indicate that these Fe oxyhydroxide particles are dominated by ferrihydrite.