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The Effects of Using Alkali-Silica Reaction Affected Recycled Concrete Aggregate in Hot Mix AsphaltGeiger, Brian James 2010 August 1900 (has links)
The effects of using alkali-silica reaction (ASR) affected recycled concrete
aggregate (ASR-RCA) in hot mix asphalt (HMA) were investigated in this study.
Dilatometer and modified beam tests were performed to determine the possibility of new
ASR occurring in reactive aggregates within the HMA or re-expansion of existing gel.
The Lottman test and micro-calorimeter were used to determine the moisture
susceptibility of HMA made with ASR-RCA. A differential scanning calorimeter
(DSC) with thermogravimetric analysis (TGA) was used to evaluate the drying of an
artificial gel and x-ray diffraction (XRD) was used to check for the potential presence of
gel in the filler fraction of the ASR-RCAs. Micro-deval and freeze-thaw tests were
evaluated for their potential to indicate the presence of excess micro-cracks or ASR gel.
Expansion testing indicated that both ASR-RCAs were still reactive with 0.5 N
NaOH solution saturated with calcium hydroxide (CH) at 60 degrees C. Dilatometer testing of
HMA specimens in NaOH CH solution at 60 degrees C indicated a reaction between the asphalt
binder and the solution, but little, if any, ASR. The lack of expansion in the modified
beam test supports the binder-solution interaction. However, dilatometer testing in
deicer solution at the same temperature indicated that some ASR may have occurred
along with the primary binder-solution interaction. The volume change characteristics
associated with the binder-solution interaction with and without ASR was supported by
the change in pH and alkali concentration of the test solution.
DSC/TGA testing indicated that the artificial gel dehydrated at approximately
100 degrees C. XRD analysis of the filler indicated that some gel may have accumulated in this
fraction. Moisture damage testing indicated good resistance to moisture damage by
HMA mixtures made with ASR-RCA especially compared to a virgin siliceous
aggregate. Micro-deval and freeze-thaw tests can detect the presence of micro-cracks
due to ASR in ASR-RCAs as higher mass loss than the virgin aggregate.
The potential distress mechanisms that may occur when using ASR-RCA in an
HMA pavement were identified. Results obtained using accelerated laboratory
conditions were extrapolated based on anticipated field conditions. Guidelines for the
mitigation of potential distresses in HMA made with ASR-RCA are presented.
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Probabilistic analysis of air void structure and its relationship to permeability and moisture damage of hot mix asphaltCastelblanco Torres, Adhara 12 April 2006 (has links)
The permeability of hot mix asphalt (HMA) is of special interest to engineers and researchers due to the effects that water has on asphalt pavement performance. Significant research has been done to study HMA permeability. However, most of the studies primarily focused on relating permeability to the average percent air voids in the mix. Such relationships cannot predict permeability accurately due to the different distributions of air void structures at a given average percent of air voids. Air void distribution is a function of many factors such as mix design, compaction method, and aggregate properties. Recent advances in X-ray computed tomography and image analysis techniques offer a unique opportunity to better quantify the air void structure and, consequently, predict HMA permeability.
This study is focused on portraying permeability as a function of air void size distribution by using a probabilistic approach that was previously developed by Garcia Bengochea for soils. This approach expresses permeability as a function of the probability density function (pdf) of the air void size distribution. Equations are derived in this thesis to describe this relationship for laboratory specimens compacted using the linear kneading compactor (LKC) and Superave^TM gyratory compactor (SGC) as well as for field cores (labeled as MS). A good correlation exists between permeability and the pdf of the air voids that formed the flow paths (i.e. connected voids).
The relationship between moisture damage, air void structure, and cohesive and adhesive bond energy is also investigated in this study. Moisture damage is evaluated by monitoring changes in mechanical properties due to moisture conditioning. The influence of air void structure on pore pressure is studied using a recently developed program at Texas A&M University that simulates fluid flow and pore pressure in a porous medium. The surface free energy of the aggregates and asphalt are calculated from laboratory measurements using the Universal Sorption Device (USD) and the Wilhelmy Plate method, respectively, in order to test the compatibility of the aggregates with the asphalt in the presence of water.
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Development of methods to quantify bitumen-aggregate adhesion and loss of adhesion due to waterBhasin, Amit 17 September 2007 (has links)
Moisture induced damage of hot mix asphalt pavements has a significant
economic impact in terms of excessive maintenance and rehabilitation costs. The
moisture sensitivity of an asphalt mix depends on the combined effects of material
properties, mixture design parameters, loading conditions and environmental factors.
Traditional methods to assess moisture sensitivity of asphalt mixes rely on mechanical
tests that evaluate the mix as a whole. These methods do not measure material properties
and their role in moisture sensitivity of the mix independently. This information is very
important to select materials resistant to moisture induced damage, or to modify locally
available materials to improve their resistance to moisture damage for economic reasons.
The objective of this research is to develop experimental and analytical tools to
characterize important material properties that influence the moisture sensitivity of
asphalt mixes.
Quality of adhesion between the aggregate and bitumen binder in wet and dry
conditions plays an important role on the moisture sensitivity of the asphalt mix. A part
of this research work was to develop the Wilhelmy plate method and the Universal
Sorption Device to measure the surface free energy components of the bitumen and
aggregate with adequate precision and accuracy, respectively. Surface energy of these
materials was used to identify parameters based on thermodynamics that can quantify
their interfacial adhesion and propensity to debond in the presence of water. The
thermodynamic parameters were shown to correlate well with the moisture sensitivity of
asphalt mixes determined from laboratory tests. Specific surface areas of the aggregates
were also used to account for the influence of mechanical interlocking at the micro scale.
In some mixes, chemical bonding also contributes to the adhesion between bitumen and aggregate. The use of a micro calorimeter was introduced in this research as a versatile
and fast tool to quantify the combined effects of physical and chemical adhesion between
these materials.
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Performance Evaluation of Recycled Asphalt Shingles (RAS) in Hot Mix Asphalt (HMA): An Ontario PerspectiveIslam, Riyad-UL 07 April 2011 (has links)
Today, a large quantity of waste is generated from the replacement of residential and commercial roofs. Many of the roofs being upgraded with previously constructed from asphalt shingles. Recycled Asphalt Shingles (RAS) contain nearly 30% of asphalt cement by mass, which can be a useful additive to asphalt pavements. In addition, shingles can offer significant potential savings through recycling and recovery as a construction material in flexible pavement. Currently, one and a half million tons of roofing shingle waste is generated each year in Canada related to the replacement of residential and commercial roofs and 90% of this valuable material is sent to landfills. If engineered properly, the addition of RAS into Hot Mix Asphalt (HMA) can provide significant benefits. The University of Waterloo’s Centre for Pavement and Transportation Technology (CPATT) is committed to working with public and private sector partners to develop sustainable technologies for the pavement industry. Using RAS in HMA can lead to economical, environmental and social benefits. Examples of which are reduced waste going to landfills and a reduction in the quantity of virgin material required.
This research has involved the Ontario Centres of Excellence (OCE) and Miller Paving Limited. It was conducted to evaluate the performance of HMA containing RAS in both field and laboratory tests. A varying percentage of RAS was added to six common Ontario surface and binder layer of asphalt mixes. The intent was to determine if RAS could be added to improve performance and provide longer term cost savings. Laboratory testing was performed to evaluate the mix behavior. The elastic properties, fatigue life and resistance to thermal cracking were all evaluated at the CPATT laboratory. The characteristics of the mixes were evaluated by carrying out Dynamic Modulus, Resilient Modulus, Flexural Fatigue and Thermal Stress Restrained Specimen Test (TSRST) tests following American Association of State Highway and Transportation Officials (AASHTO) and American Society for Testing and Materials (ASTM) standards. Field test sections were constructed from HMA containing RAS to monitor the pavement behavior under natural environmental and traffic loading conditions. Evaluation of the field sites was performed using a Portable Falling Weight Deflectometer (PFWD) and carrying out distress surveys following the Ministry of Transportation Ontario (MTO) guidelines. The results to date show the sections performing very well with minimal to no distress developing.
The results of the laboratory testing and field performance evaluations have shown encouraging results for the future use of RAS in HMA. If RAS can properly be engineered into HMA it can be a useful additive in both the surface and binder layers of the flexible pavement structure. Ultimately, the use of RAS in HMA can provide both an environmentally friendly and cost effective solution to the Ontario paving industry.
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A Comprehensive Evaluation of Hot Mix Asphalt versus Chemically Modified Warm Mix AsphaltWakefield, Amma January 2011 (has links)
Warm mix asphalt (WMA) technology has now been successfully used in Ontario for a few years. This shift in usage relates to extensions in construction season, reduced emissions, larger compaction windows, and potential fuel savings. This research between Miller Paving Ltd. and the Centre for Pavement and Transportation Technology attempts to better quantify the difference in hot mix asphalt (HMA) and WMA. The object of this study was three-fold.
The first part of the research was to examine the strength characteristics of HMA and WMA as a function of storage time. The purpose of this evaluation was to quantify indirect tensile strength (ITS) and moisture susceptibility of HMA and WMA over time.
The second objective involved evaluating the performance characteristics of HMA and WMA. Resilient modulus and dynamic modulus testing were completed on plant-produced HMA and WMA material, which was used to determine long-term performance properties of both mixes.
The third and final objective of this study was an economic analysis performed to determine the difference in cost for construction and maintenance for the HMA and WMA pavements. This was completed to determine if the cost of the warm mix technology used in the production of the WMA was offset by fuel savings at the plant.
The findings of the research included:
• HMA and WMA had statistically equivalent air voids over a four-week storage period.
• Dry and wet ITS results for the WMA increased over a four-week storage period while the HMA specimens did not show this same increase.
• WMA material had slightly better workability than the HMA material although the values were statistically equivalent.
• WMA mix had higher resilient modulus values than the HMA mix.
• Dynamic modulus testing showed that at high temperatures, WMA showed to be slightly more susceptible to rutting than the HMA mix, and at lower temperatures, the HMA showed to be slightly more susceptible to fatigue cracking than the WMA mix.
• The MEPDG showed that both the HMA and WMA pavements were deemed to be structurally adequate.
• An economic analysis of the HMA and WMA pavements compared a life cycle cost analysis over a 20-year design life which included all costs associated with construction, maintenance, and rehabilitation of both the HMA and WMA and showed that the HMA was slightly more cost effective than the WMA.
• A field trial was performed by Miller Paving Limited on Highway 62 in Madoc, Ontario showed that the WMA material was more effective at maintaining the temperature of the asphalt mixture during long hauling distances.
• Overall the WMA exhibited the same performance properties as the HMA.
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Relationships between laboratory measured characteristics of HMA and field compactabilityLeiva Villacorta, Fabricio, January 2007 (has links) (PDF)
Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 114-117)
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Development of a non-solvent based test method for evaluating reclaimed asphalt pavement mixesCarter, Alan. Stroup-Gardiner, Mary, January 2005 (has links) (PDF)
Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Includes bibliographic references (p.82-87).
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Verification of the superpave gyratory Ndesign compaction levelsProwell, Brian Douglas, Brown, E. R. January 2006 (has links) (PDF)
Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.183-191).
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Estudo de misturas laterita-asfalto da região metropolitana de Belém-PA para revestimentos de pavimento. / Study of using a non-conventional aggegate, the lateritic gravel in asphalt concrete mixtures.Simonne da Costa Amaral 16 June 2004 (has links)
No Estado do Pará, convencionalmente são empregados rocha britada ou seixo rolado natural como agregados nas misturas asfálticas. Nas proximidades da região metropolitana de Belém, não há disponibilidade destes materiais, obrigando o transporte destes agregados de boa qualidade de pedreiras e jazidas distantes mais de 170 Km, aumentando consideravelmente os custos de pavimentação. Com o objetivo de redução de custos, buscou-se o estudo de um outro agregado natural nãoconvencional, a laterita, abundante nas proximidades de Belém. Três tipos de ligantes asfálticos foram utilizados nas misturas asfálticas pesquisadas: um asfalto convencional CAP de penetração 50-60 proveniente da refinaria da LUBNOR, no Ceará; um asfalto da refinaria da REMAN da Amazônia modificado por asfaltita; e um asfalto-borracha da região sudeste. Uma quarta alternativa da mistura asfáltica foi considerada, empregando conjuntamente laterita e seixo rolado como agregados. Foi realizada uma análise comparativa das misturas asfálticas baseada em ensaios laboratoriais tais como: dosagem Marshall, danos por umidade induzida, deformação permanente em simulador de tráfego, resistência à tração por compressão diametral, módulo de resiliência e fadiga. Um processo inovador foi concebido para separação e lavagem das lateritas. Os resíduos desta seleção de agregados foram testados de modo a viabilizar seu emprego como material de base ou sub-base. Foi realizada também uma breve análise mecanicista de estruturas de pavimentos com o auxílio do programa ELSYM 5. Concluiu-se que as misturas asfálticas com laterita lavada podem ser usadas em revestimentos de pavimento de vias públicas e de rodovias de baixo volume tráfego obtendo-se os melhores resultados para as misturas de lateritaasfalto com o ligante modificado por asfaltita. / Crushed igenous rocks and washed quartzite gravels are conventional aggregates for asphalt mixes in the State of Pará, northern Brazil. However, these materials are not available in many parts of the state, specially near the city of Belem, the state capital. The current practice is to import these high quality aggregates from the few quarries located in remote sites, leading to a considerable increase in construction costs. To cut down costs, it is necessary to look for alternative sources of natural aggregates. This study attempts to present an alternative solution for asphalt mixtures using a non-conventional natural aggregate: laterites, which are widely available in the metropolitan area. Three types of asphalt binders were used: a conventional one AC penetration of 50-60, an asphalt cement modified by gilsonite, and an asphalt rubber. A fourth type of asphalt mix was considered, using washed quartzite gravels in addition to the laterite. A comparative analysis was conducted using parameters obtained from laboratory tests like Marshall design, stripping test, wheel tracking test, indirect tensile strength, resilient modulus, and fatigue life. An innovative process was developed to clean the laterite by water washing. Residuals from the process were tested regarding its possible use as a material for pavement base or subbase. Finally, a mechanistic analysis was performed, using ELSYM 5 software. Results indicate a good performance to the hot-mixes and the one with gilsonite modified binder presented the best performance.
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Comparison of Surface Characteristics of Hot-Mix Asphalt Pavement Surfaces at the Virginia Smart RoadDavis, Robin Michelle 01 August 2001 (has links)
Pavement surface characteristics are important to both the safety of the pavement surface and the comfort of the drivers. As of yet, texture and friction measurements have not been incorporated into the design of pavement surfaces. Seven different wearing surface mixtures, placed at the Virginia Smart Road pavement facility, were studied over a one year time period for both friction and texture properties. A locked wheel skid trailer and a laser profilometer were used to assess the pavement surface characteristics. Laboratory testing of the pavement wearing surface mixtures was performed to determine volumetric and mixture specific characteristics. Testing included gyratory compaction, specific gravity, maximum theoretical specific gravity, ignition testing, and gradation analysis. These material properties were used to study the impact of material properties on pavement surface characteristics. The pavement surface characteristics were analyzed using regression analysis with some measured and calculated parameters relevant to the pavement wearing surface properties. Analysis variables included the skid number at 64 kilometers per hour measured using the ASTM E501 (smooth) and ASTM E524 (ribbed) tires, the mean profile depth, the slope of a linear SN-speed model, the skid number at zero speed from the Pennsylvania State University (1) model, and the International Friction Index parameters.
Analysis determined that testing particulars such as the grade of the test did not significantly affect the measured skid number. However, there is a significant difference between the skid numbers measured using the two tires. Additionally, the relationship between speed and skid resistance is assessed differently between the two test tires. Regression analysis concluded that there is a relationship between surface characteristics and HMA design properties such as the VMA, VTM, Percent Passing #200 sieve, and Binder Type. The influence of these variables on each of the analysis parameters varied. / Master of Science
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