Paving asphalts : asphalt aggregate interactions and asphalt intermolecular interactions /

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Comparison of the R-70 self-heating rate of New Zealand and Australian coals to Suggate rank parameter

Samples from New Zealand and Australia have been tested in an adiabatic oven to assess the effect of rank on the R-70 selfheating rate of coal. A non-linear relationship can be defined for coals from both countries using the revised Suggate rank (S-r) parameter. Subbituminous coals have the highest R-70 self-heating rate values, which are 20 times that of high volatile A bituminous coals on a dry mineral matter free basis (similar to 1 cf. 20 degrees C h(-1)). However, the moderating effects of moisture and mineral matter can reduce this difference to only 2-3 times for coal in-situ. (c) 2005 Elsevier B.V All rights reserved.

Kinetics of reduction of FeO from slag by graphite and coal chars

The rates of reduction of FeO from iron-saturated FeO-CaO-Al2O3-SiO2 slags by graphite, coke, bituminous coal and anthracitic coal chars at temperatures in the range 1 673-1873 K have been measured using a sessile drop technique. The extents of reaction were determined using EPMA analysis of quenched samples, and on line gas analysis using a quadrupole mass spectrometer. The reaction rates have been shown to be dependent critically on carbon type. For the reaction geometry used in this investigation the reduction rates of graphite and coke are observed to be faster than with coal chars. This unexpected finding is shown to be associated with differences in the dominant chemical and mass transfer mechanisms occurring at the reaction interface. High reaction rates are observed to occur with the formation of liquid Fe-C alloy product and the associated gasification of carbon from the alloy. The rates of reduction by coal chars are determined principally by the chemical reaction at the carbon/gas interface and slag phase mass transfer.

Factors affecting hot spot development in bulk coal and associated gas evolution

There are many physical factors that can affect the self-heating rate of coal. The presence of seam gas has often been referred to as inhibiting coal self-heating due to the limited access of oxidation sites created by the presence of the gas adsorbed on the coal pores. Similarly, the presence of bed moisture in the coal also acts as an inhibitor of oxidation by blocking access of air into the pores. Gas drainage of a coal seam prior to mining removes both gas and moisture from the seam. Bulk coal self-heating tests in a two-metre column on both gassy, as-mined and gas-drained, dried high volatile bituminous coal show that removal of gas and moisture from the coal accelerates the rate of self-heating to thermal runaway from 8.5 days to 4.25 days, from a start temperature of 30°C, with an airflow of 0.25 L/min. The corresponding gas evolution pattern for each of these situations is different. Therefore, it is necessary to take this change in coal condition into consideration when developing a spontaneous combustion management plan.

The performance of cement stabilised minestone

This study is concerned with the durability of cement stabilised minestone (CSM). Minestone is dominated by the clay-bearing mudrocks and shales of the Coal Measures. Consequently, engineering problems are often encountered due to the likelihood of these rocks undergoing volume change and degradation when exposed to fluctuations in moisture content. In addition, iron sulphides (chiefly pyrite) are frequently present in minestone as diagenetic minerals which on excavation have the potential to oxidise forming sulphate minerals. The oxidation of sulphides may in itself contribute to volume increase in pyritic rocks and sulphate minerals may combine with the products of cement hydration to produce further expansion. The physical and chemical properties of a wide range of minestones are determined and attempts are made to correlate these with the engineering performance of cement stabilised specimens subjected to short-term immersion in water. Criteria, based on these raw material indices are proposed with a view to eliminating minestones which are unsuitable. A long-term durability study is also described. In this, the geochemical stability of pyrite in CSM was examined together with the role played by the sulphur bearing mineralogy in determining the engineering performance of CSM's exposed to conditions of increased moisture availability. The nature of a number of disrupted CSM pavements which have been examined are also discussed.

Intermediate pyrolysis of biomass energy pellets for producing sustainable liquid, gaseous and solid fuels

This work describes the use of intermediate pyrolysis system to produce liquid, gaseous and solid fuels from pelletised wood and barley straw feedstock. Experiments were conducted in a pilot-scale system and all products were collected and analysed. The liquid products were separated into an aqueous phase and an organic phase (pyrolysis oil) under gravity. The oil yields were 34.1 wt.% and 12.0 wt.% for wood and barley straw, respectively. Analysis found that both oils were rich in heterocyclic and phenolic compounds and have heating values over 24 MJ/kg. The yields of char for both feedstocks were found to be about 30 wt.%, with heating values similar to that of typical sub-bituminous class coal. Gas yields were calculated to be approximately 20 wt.%. Studies showed that both gases had heating values similar to that of downdraft gasification producer gas. Analysis on product energy yields indicated the process efficiency was about 75%. © 2014 Elsevier Ltd. All rights reserved.

Anisotropic characterization of crack growth in the tertiary flow of asphalt mixtures in compression

Asphalt mixtures exhibit primary, secondary, and tertiary stages in sequence during a rutting deterioration. Many field asphalt pavements are still in service even when the asphalt layer is in the tertiary stage, and rehabilitation is not performed until a significant amount of rutting accompanied by numerous macrocracks is observed. The objective of this study was to provide a mechanistic method to model the anisotropic cracking of the asphalt mixtures in compression during the tertiary stage of rutting. Laboratory tests including nondestructive and destructive tests were performed to obtain the viscoelastic and viscofracture properties of the asphalt mixtures. Each of the measured axial and radial total strains in the destructive tests were decomposed into elastic, plastic, viscoelastic, viscoplastic, and viscofracture strains using the pseudostrain method in an extended elastic-viscoelastic correspondence principle. The viscofracture strains are caused by the crack growth, which is primarily signaled by the increase of phase angle in the tertiary flow. The viscofracture properties are characterized using the anisotropic damage densities (i.e., the ratio of the lost area caused by cracks to the original total area in orthogonal directions). Using the decomposed axial and radial viscofracture strains, the axial and radial damage densities were determined by using a dissipated pseudostrain energy balance principle and a geometric analysis of the cracks, respectively. Anisotropic pseudo J-integral Paris' laws in terms of damage densities were used to characterize the evolution of the cracks in compression. The material constants in the Paris' law are determined and found to be highly correlated. These tests, analysis, and modeling were performed on different asphalt mixtures with two binders, two air void contents, and three aging periods. Consistent results were obtained; for instance, a stiffer asphalt mixture is demonstrated to have a higher modulus, a lower phase angle, a greater flow number, and a larger n1 value (exponent of Paris' law). The calculation of the orientation of cracks demonstrates that the asphalt mixture with 4% air voids has a brittle fracture and a splitting crack mode, whereas the asphalt mixture with 7% air voids tends to have a ductile fracture and a diagonal sliding crack mode. Cracks of the asphalt mixtures in compression are inclined to propagate along the direction of the external compressive load. © 2014 American Society of Civil Engineers.

A methodological framework for modeling pavement maintenance costs for projects with performance-based contracts

Performance-based maintenance contracts differ significantly from material and method-based contracts that have been traditionally used to maintain roads. Road agencies around the world have moved towards a performance-based contract approach because it offers several advantages like cost saving, better budgeting certainty, better customer satisfaction with better road services and conditions. Payments for the maintenance of road are explicitly linked to the contractor successfully meeting certain clearly defined minimum performance indicators in these contracts. Quantitative evaluation of the cost of performance-based contracts has several difficulties due to the complexity of the pavement deterioration process. Based on a probabilistic analysis of failures of achieving multiple performance criteria over the length of the contract period, an effort has been made to develop a model that is capable of estimating the cost of these performance-based contracts. One of the essential functions of such model is to predict performance of the pavement as accurately as possible. Prediction of future degradation of pavement is done using Markov Chain Process, which requires estimating transition probabilities from previous deterioration rate for similar pavements. Transition probabilities were derived using historical pavement condition rating data, both for predicting pavement deterioration when there is no maintenance, and for predicting pavement improvement when maintenance activities are performed. A methodological framework has been developed to estimate the cost of maintaining road based on multiple performance criteria such as crack, rut and, roughness. The application of the developed model has been demonstrated via a real case study of Miami Dade Expressways (MDX) using pavement condition rating data from Florida Department of Transportation (FDOT) for a typical performance-based asphalt pavement maintenance contract. Results indicated that the pavement performance model developed could predict the pavement deterioration quite accurately. Sensitivity analysis performed shows that the model is very responsive to even slight changes in pavement deterioration rate and performance constraints. It is expected that the use of this model will assist the highway agencies and contractors in arriving at a fair contract value for executing long term performance-based pavement maintenance works.

A Methodological Framework for Modeling Pavement Maintenance Costs for Projects with Performance-based Contracts

Performance-based maintenance contracts differ significantly from material and method-based contracts that have been traditionally used to maintain roads. Road agencies around the world have moved towards a performance-based contract approach because it offers several advantages like cost saving, better budgeting certainty, better customer satisfaction with better road services and conditions. Payments for the maintenance of road are explicitly linked to the contractor successfully meeting certain clearly defined minimum performance indicators in these contracts. Quantitative evaluation of the cost of performance-based contracts has several difficulties due to the complexity of the pavement deterioration process. Based on a probabilistic analysis of failures of achieving multiple performance criteria over the length of the contract period, an effort has been made to develop a model that is capable of estimating the cost of these performance-based contracts. One of the essential functions of such model is to predict performance of the pavement as accurately as possible. Prediction of future degradation of pavement is done using Markov Chain Process, which requires estimating transition probabilities from previous deterioration rate for similar pavements. Transition probabilities were derived using historical pavement condition rating data, both for predicting pavement deterioration when there is no maintenance, and for predicting pavement improvement when maintenance activities are performed. A methodological framework has been developed to estimate the cost of maintaining road based on multiple performance criteria such as crack, rut and, roughness. The application of the developed model has been demonstrated via a real case study of Miami Dade Expressways (MDX) using pavement condition rating data from Florida Department of Transportation (FDOT) for a typical performance-based asphalt pavement maintenance contract. Results indicated that the pavement performance model developed could predict the pavement deterioration quite accurately. Sensitivity analysis performed shows that the model is very responsive to even slight changes in pavement deterioration rate and performance constraints. It is expected that the use of this model will assist the highway agencies and contractors in arriving at a fair contract value for executing long term performance-based pavement maintenance works.

(Table 2, Page 106-107) Composition of the HCl-soluble fraction in Barents Sea iron-manganese deposits

Ferromanganese concretions from ten stations in the Barents Sea have been analysed for 24 elements. The deposits occur as discoidal and flat concretions and as coatings, in the latter case on lithified or detrital material or as extensive pavements on the Svalbard shelf. The concretions are compositionally similar to Baltic concretions but differ considerably from deep-ocean nodules, particularly in Cu, Ni and Co contents. Statistical analyses reveal distinct correlations between Mn, Na, Ba, Ni and Cu; the Mn-rich coatings showed enrichment of Mo, Zn and possibly Co in a Mn-phase. The iron phase holds high concretions of P and As. Two iron-rich concretions with high contents of P, Ca, Sr, Y, Yb and La were found east and northeast of Spitsbergen Banken, probably indicating upwelling of nutrient-rich, cold polar water along the Svalbard shelf.

Observations and rare earth element composition of manganese nodules during Atlantis cruise AT266, Blake Plateau

An area of about 22,000 km² on the northern Blake Plateau, off the coast of South Carolina, contains an estimated 2 billion metric tons of phosphorite concretions, and about 1.2 billion metric tons of mixed ferromanganese-phosphorite pavement. Other offshore phosphorites occur between the Blake Plateau and known continental deposits, buried under variable thicknesses of sediments. The phosphorite resembles other marine phosphorites in composition, consisting primarily of carbonate-fluorapatite, some calcite, minor quartz and other minerals. The apatite is optically pseudo-isotropic and contains about 6% [CO3]**2- replacing [PO4]**3- in its structure. JOIDES drillings and other evidence show that the phosphorite is a lag deposit derived from Miocene strata correlatable with phosphatic Middle Tertiary sediments on the continent. It has undergone variable cycles of erosion, reworking, partial dissolution and reprecipitation. Its present form varies from phosphatized carbonate debris, loose pellets, and pebbles, to continuous pavements, plates, and conglomeratic boulders weighing hundreds of kilograms. No primary phosphatization is currently taking place on the Blake Plateau. The primary phosphate-depositing environment involved reducing conditions and required at least temporary absence of the powerful Gulf Stream current that now sweeps the bottom of the Blake Plateau and has eroded away the bulk of the Hawthorne-equivalent sediments with which the phosphorites were once associated.

Annotated record of the detailed examination of ferromanganese concretions from the Svalbard shelf in the Barents Sea

Ferromanganese concretions from ten stations in the Barents Sea have been analysed for 24 elements. The deposits occur as discoidal and flat concretions and as coatings, in the latter case on lithified or detrital material or as extensive pavements on the Svalbard shelf. The concretions are compositionally similar to Baltic concretions but differ considerably from deep-ocean nodules, particularly in Cu, Ni and Co contents. Statistical analyses reveal distinct correlations between Mn, Na, Ba, Ni and Cu; the Mn-rich coatings showed enrichment of Mo, Zn and possibly Co in a Mn-phase. The iron phase holds high concretions of P and As. Two iron-rich concretions with high contents of P, Ca, Sr, Y, Yb and La were found east and northeast of Spitsbergen Banken, probably indicating upwelling of nutrient-rich, cold polar water along the Svalbard shelf.

Viabilidade técnica da fabricação de compósito utilizando fibra de pneu na fabricação de blocos intertravados

This work aims to demonstrate the feasibility of a ceramic composite containing fiber in the rubber manufacturing interlocking blocks. Gravel, sand, cement, rubber and fiber: the processes of manufacture and assembly of blocks produced and the various formulations studied with different proportions between the constituent elements were addressed. Mechanical properties were determined for the different formulations, compressive strength, diametral compressive strength, water absorption and apparent density, obeying the rules related to each property. It was concluded that the addition of rubber fiber gave the concrete studied resistance lower than conventional concrete which can be verified on the microstructural analysis obtained by SEM, which revealed the presence of pores and the low adhesion between the fiber and the matrix compression (tire fiber / cement paste). The composite of more viable tire BCPB1 (1/2) fiber can be used in places requests as light squares, pavements, roads and other cycle as well as in the manufacture of the curb and gutter, by having compressive strength in about 20 MPa

Utilização do resíduo grosso do beneficiamento da scheelita em aplicações rodoviárias

Mining is an activity of great economic and social value, assisting in the development of the country. However, it can be extremely harmful to the environment if no proper waste management study exists as mitigation measure its effects. Sample some of these harmful effects are pollution: water, through the seepage of waste into the groundwater; soil; of fauna and flora; sound (due to the noise of machines); visual from the residue stored in the open, changing the local landscape; and air. One way to mitigate environmental impacts caused by mining is the proper management of their waste through their use on highways. To that end, this paper proposes to give an appropriate destination to grit coming from the beneficiation of scheelite, due to mining activity from mining group Tomaz Salustino in Brejuí mine, located in the city of Currais Novos in the state of Rio Grande do Norte. This work was developed in four stages. The first comprised the chemical and mineralogical tests, DRX and FRX in which they sought to discover the composition of the material studied. The next step involved the physical characteristics of the waste by means of specific tests and grinding the solid mass, LL and LP. The third stage included the specific tests applied to the pavement, with the compaction test and test Index Support California. Finally, the fourth stage was the mechanical characterization, represented by direct shear tests, both in the flooded condition and not in flooded condition. The technical feasibility of using the modified energie compacted in layers of subbase power has been verified. In normal and intermediate energies is feasible to use less noble as layers as the subgrade. The incorporation of the waste in layers of road pavements provide an alternative to conventionally used in paving aggregates, providing a proper disposal of tailings from scheelite, as well as environmental preservation

Caracterização de resíduos oriundos do beneficiamento do minério de ferro para uso em pavimentação

Mining in Brazil has a key role in economic and social development, contributing directly to improve the lives of the population. However, the mining activity even if done responsibly and with a proper study of waste management to reduce the impact of its effects, may cause harmful damage to the environment. Other forms of pollution are also caused due to mining activity. The visual pollution caused by the waste storage at open sky, in addition to the noise pollution caused by the excessive noise of the machines both in the extraction of ore, as in processing. An alternative way to lessen the environmental impacts caused by mining is the use of waste in layers that will compose the pavements along the highways. Thus, this work sets out to give a proper disposal of the wastes from the processing of iron ore, resulting from the mining activity of the group of mining Mhag Services and Mining S/A, in the mine of Bonito, located in Jucurutu, a town in the state of Rio Grande do Norte. The residues of the iron ore were stabilized with a granular soil from the city of Macaiba, also in the state of Rio Grande do Norte, which is being used in the duplication of the BR-304 referring to the entitled passage of Reta Tabajara. The present work was developed in three stages, being the first one divided by the chemical and mineralogical tests, by the tests of physical characterization and by the tests of paving for the residues of the iron ore. The second stage corresponds to the same tests being performed for granular soil. The third stage includes the essays abovementioned for three different mixtures of iron ore waste and granular soil, being they: 15% of iron-ore waste and 85% of granular soil, 25% of iron-ore waste and 75% of granular soil, 50% of iron-ore waste and 50% of granular soil. The technical feasibility of using waste from the iron ore beneficiation was checked, compressed in the intermediate energy and modified for use in base layers, sub-base, reinforcement subgrade and subgrade. The incorporation of the residues originating from the improvement of the iron ore in highways will provide an alternative to the use of aggregate conventionally used in the paving, besides preserving the environment.