Many state departments of transportation set tolerances for the accuracy of dowel-bar placement i... more Many state departments of transportation set tolerances for the accuracy of dowel-bar placement in a concrete-pavement joint. By limiting the allowable misalignment of dowel bars, these tolerances are designed to improve bar placement at the joints and thus increase the load transfer efficiency. This article discusses a research project undertaken to determine whether attaching a crack initiator to the middle of the dowel bar in a concrete-pavement joint could control the path of cracking in concrete pavements. The aim was to ensure the crack would propagate through the middle of the dowel bar.
... Goumans/Senden/van der Sloot, Editors Waste Materials in Construction: Putting Theory into Pr... more ... Goumans/Senden/van der Sloot, Editors Waste Materials in Construction: Putting Theory into Practice .91997 Elsevier Science BV All rights ... Behavior of Asphaltic Pavements Constructed with MSW Combustion Bottom Ash T. Taylor Eighmy, Douglas Crimi, Ingrid E. Whitehead ...
The work involves research on investigating techniques and procedures to assess the Alkali Silica... more The work involves research on investigating techniques and procedures to assess the Alkali Silica Reactivity (ASR) expansion potential for concrete made from recycled concrete aggregate (RCA) which was known to have ASR, or is capable of ASR under conditions of increased alkali. Laboratory testing was done to evaluate various testing procedures designed to accelerate the ASR reaction. This included evaluating prisms with variable surface to volume ratios, increased moisture state, and microwave energy. Standard 280 mm prisms with 76.2 mm faces cast with four 6.35 mm parallel longitudinal holes were shown to not only accelerate ASR but also to lower the coefficient of variation of the expansion data. Expansion of 76.2 mm concrete cubes was found to be significantly accelerated as compared to that of a standard prism. Sealing prisms in evacuated plastic bags with water was also found to effectively accelerate ASR expansion. Concrete prisms were subjected to ASTM C 1260 and ASTM C 1293 conditions and the results were compared to those from modified versions of the same tests including the use of microwaves.
ABSTRACTQuasi-elastic neutron scattering provides detailed information of the atomic and molecula... more ABSTRACTQuasi-elastic neutron scattering provides detailed information of the atomic and molecular interactions responsible for a material's properties and is a direct and nondestructive method of measuring the motion of hydrogen. This technique was utilized to evaluate the state of water in a cementitious material. The relative amount of freezable water that existed in a saturated type I portland cement paste with water/cement ratios of 0.3, 0.4, and 0.5 was determined over a temperature ranging from +3 C to - 40 C. The amount of frozen water relative to the total water content was related to the water filled pore size predicted to be freezable at each temperature. The proportion of immobilized water increased for all water cement ratios gradually with decreasing temperatures below 0 C until most of the water was immobile at -40 C. The relative proportion of immobile water at 3 C was found to be inversely related to the water/cement ratio, which suggested a smaller fraction of ...
The seawater leachability of cadmium and lead sludges solidified in portland cement paste was inv... more The seawater leachability of cadmium and lead sludges solidified in portland cement paste was investigated. The leachates of the wastes containing cadmium and lead were analyzed for metal contents using flame atomic absorption spectrophotometry (AAS) as well as pH and alkalinity. A control sample containing only portland cement paste was also leached to serve as a comparison. Results show that the total cadmium leached from the stabilized waste over a 50‐day period was about 1.0% of the total cadmium added to the paste. Lead was not detected in the leachate, however, this could be due to physical and analytical interferences associated with lead. The pH and alkalinity data show that initially, hydroxide is leached from the waste and calcium carbonates are formed on the particle surfaces. After a 50‐day period, the pH and alkalinity of the waste leachates approach that of the seawater leachant.The microstructure of the waste samples was investigated using scanning electron microscopy...
ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel ... more ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel source for the production of power. An experimental test burn partially substituting coal with RDF was undertaken by the Public Service of New Hampshire at the Merrimack Power Station.Five percent and ten percent RDF were substituted, on a BTU basis, for coal in the test bums. The chemical and physical properties of the resulting fly ash were determined. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. Emphasis was placed on investigating the effect of the RDF fly ash on Portland cement concrete.Most of the chemical and physical properties of the coal-RDF fly ash were found to be comparable with ordinary coal fly ash except for the amount of cadmium and lead, the pozzolanic activity index and the compressive strength of fly ash concrete. Cadmium and lead were at average levels of 5.1 ppm and 102.6 ppm for the 5% RDF, and 7.8 ppm and 198.3 ppm for the 10% RDF, r...
Transportation Research Record: Journal of the Transportation Research Board, 2009
A 1994 field survey was undertaken of pavements containing recycled concrete aggregate (RCA) cons... more A 1994 field survey was undertaken of pavements containing recycled concrete aggregate (RCA) constructed in Connecticut, Kansas, Minnesota, Wisconsin, and Wyoming. These pavements were resurveyed during the summer of 2006 to update their performance after they had been subjected to 12 more years of traffic. Additional pavements made with RCA from Illinois and Iowa were also observed in 2006. Although the recycled pavements contain higher mortar contents, there was no clear correlation between the higher total mortar content of RCA concrete pavements and cracking distresses in either survey, although one RCA concrete pavement did exhibit more cracking than the control pavement. Overall there was little difference between the 1994 and 2006 surveys. Several pavements were rehabilitated by the addition of dowels for load transfer. These pavements are performing exceptionally well and show that rehabilitation techniques normally applied to conventional concrete work effectively on recycl...
The seawater leachability of portland cement solidified cadmium and lead wastes is investigated. ... more The seawater leachability of portland cement solidified cadmium and lead wastes is investigated. The synthetic seawater leachates were analyzed for metals content using atomic absorption spectrophotometry. The pH and alkalinity of the leachate was also measured. The cumulative cadmium release after 46 days of leaching was approximately 1.0 percent of the initial total amount added to the portland cement mixture. Lead was not detected in the leachate. The pH was initially higher and the alkalinity lower and subsequently approached the pH and alkalinity values for seawater after 30 days of leaching.The microstructure of the solidified waste was investigated using the SEM, XRD, MIP and helium pycnometry. Cadmium was detected as cadmium hydroxide while lead was not detected in crystalline form. The total porosity of cadmium and lead wastes were similar however the cadmium waste had a higher volume of pores larger than 0.2 microns.During the leaching process the surficial microstructure ...
Many state departments of transportation set tolerances for the accuracy of dowel-bar placement i... more Many state departments of transportation set tolerances for the accuracy of dowel-bar placement in a concrete-pavement joint. By limiting the allowable misalignment of dowel bars, these tolerances are designed to improve bar placement at the joints and thus increase the load transfer efficiency. This article discusses a research project undertaken to determine whether attaching a crack initiator to the middle of the dowel bar in a concrete-pavement joint could control the path of cracking in concrete pavements. The aim was to ensure the crack would propagate through the middle of the dowel bar.
... Goumans/Senden/van der Sloot, Editors Waste Materials in Construction: Putting Theory into Pr... more ... Goumans/Senden/van der Sloot, Editors Waste Materials in Construction: Putting Theory into Practice .91997 Elsevier Science BV All rights ... Behavior of Asphaltic Pavements Constructed with MSW Combustion Bottom Ash T. Taylor Eighmy, Douglas Crimi, Ingrid E. Whitehead ...
The work involves research on investigating techniques and procedures to assess the Alkali Silica... more The work involves research on investigating techniques and procedures to assess the Alkali Silica Reactivity (ASR) expansion potential for concrete made from recycled concrete aggregate (RCA) which was known to have ASR, or is capable of ASR under conditions of increased alkali. Laboratory testing was done to evaluate various testing procedures designed to accelerate the ASR reaction. This included evaluating prisms with variable surface to volume ratios, increased moisture state, and microwave energy. Standard 280 mm prisms with 76.2 mm faces cast with four 6.35 mm parallel longitudinal holes were shown to not only accelerate ASR but also to lower the coefficient of variation of the expansion data. Expansion of 76.2 mm concrete cubes was found to be significantly accelerated as compared to that of a standard prism. Sealing prisms in evacuated plastic bags with water was also found to effectively accelerate ASR expansion. Concrete prisms were subjected to ASTM C 1260 and ASTM C 1293 conditions and the results were compared to those from modified versions of the same tests including the use of microwaves.
ABSTRACTQuasi-elastic neutron scattering provides detailed information of the atomic and molecula... more ABSTRACTQuasi-elastic neutron scattering provides detailed information of the atomic and molecular interactions responsible for a material's properties and is a direct and nondestructive method of measuring the motion of hydrogen. This technique was utilized to evaluate the state of water in a cementitious material. The relative amount of freezable water that existed in a saturated type I portland cement paste with water/cement ratios of 0.3, 0.4, and 0.5 was determined over a temperature ranging from +3 C to - 40 C. The amount of frozen water relative to the total water content was related to the water filled pore size predicted to be freezable at each temperature. The proportion of immobilized water increased for all water cement ratios gradually with decreasing temperatures below 0 C until most of the water was immobile at -40 C. The relative proportion of immobile water at 3 C was found to be inversely related to the water/cement ratio, which suggested a smaller fraction of ...
The seawater leachability of cadmium and lead sludges solidified in portland cement paste was inv... more The seawater leachability of cadmium and lead sludges solidified in portland cement paste was investigated. The leachates of the wastes containing cadmium and lead were analyzed for metal contents using flame atomic absorption spectrophotometry (AAS) as well as pH and alkalinity. A control sample containing only portland cement paste was also leached to serve as a comparison. Results show that the total cadmium leached from the stabilized waste over a 50‐day period was about 1.0% of the total cadmium added to the paste. Lead was not detected in the leachate, however, this could be due to physical and analytical interferences associated with lead. The pH and alkalinity data show that initially, hydroxide is leached from the waste and calcium carbonates are formed on the particle surfaces. After a 50‐day period, the pH and alkalinity of the waste leachates approach that of the seawater leachant.The microstructure of the waste samples was investigated using scanning electron microscopy...
ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel ... more ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel source for the production of power. An experimental test burn partially substituting coal with RDF was undertaken by the Public Service of New Hampshire at the Merrimack Power Station.Five percent and ten percent RDF were substituted, on a BTU basis, for coal in the test bums. The chemical and physical properties of the resulting fly ash were determined. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. Emphasis was placed on investigating the effect of the RDF fly ash on Portland cement concrete.Most of the chemical and physical properties of the coal-RDF fly ash were found to be comparable with ordinary coal fly ash except for the amount of cadmium and lead, the pozzolanic activity index and the compressive strength of fly ash concrete. Cadmium and lead were at average levels of 5.1 ppm and 102.6 ppm for the 5% RDF, and 7.8 ppm and 198.3 ppm for the 10% RDF, r...
Transportation Research Record: Journal of the Transportation Research Board, 2009
A 1994 field survey was undertaken of pavements containing recycled concrete aggregate (RCA) cons... more A 1994 field survey was undertaken of pavements containing recycled concrete aggregate (RCA) constructed in Connecticut, Kansas, Minnesota, Wisconsin, and Wyoming. These pavements were resurveyed during the summer of 2006 to update their performance after they had been subjected to 12 more years of traffic. Additional pavements made with RCA from Illinois and Iowa were also observed in 2006. Although the recycled pavements contain higher mortar contents, there was no clear correlation between the higher total mortar content of RCA concrete pavements and cracking distresses in either survey, although one RCA concrete pavement did exhibit more cracking than the control pavement. Overall there was little difference between the 1994 and 2006 surveys. Several pavements were rehabilitated by the addition of dowels for load transfer. These pavements are performing exceptionally well and show that rehabilitation techniques normally applied to conventional concrete work effectively on recycl...
The seawater leachability of portland cement solidified cadmium and lead wastes is investigated. ... more The seawater leachability of portland cement solidified cadmium and lead wastes is investigated. The synthetic seawater leachates were analyzed for metals content using atomic absorption spectrophotometry. The pH and alkalinity of the leachate was also measured. The cumulative cadmium release after 46 days of leaching was approximately 1.0 percent of the initial total amount added to the portland cement mixture. Lead was not detected in the leachate. The pH was initially higher and the alkalinity lower and subsequently approached the pH and alkalinity values for seawater after 30 days of leaching.The microstructure of the solidified waste was investigated using the SEM, XRD, MIP and helium pycnometry. Cadmium was detected as cadmium hydroxide while lead was not detected in crystalline form. The total porosity of cadmium and lead wastes were similar however the cadmium waste had a higher volume of pores larger than 0.2 microns.During the leaching process the surficial microstructure ...
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