Fly Ash Soil Stabilization for Non-uniform Subgrade Soils: Influence of subgrade non-uniformity on PCC pavement performance PDF Download
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Author:
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ISBN:
Category : Fly ash
Languages : en
Pages : 82
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Soil treated with self-cementing fly ash is increasingly being used in Iowa to stabilize pavement subgrades, but without a complete understanding of the short- and long-term behavior. To develop a broader understanding of fly ash engineering properties, mixtures of five different soil types, ranging from ML to CH, and several different fly ash sources (including hydrated and conditioned fly ashes) were evaluated.
Author:
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ISBN:
Category : Fly ash
Languages : en
Pages : 82
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Soil treated with self-cementing fly ash is increasingly being used in Iowa to stabilize pavement subgrades, but without a complete understanding of the short- and long-term behavior. To develop a broader understanding of fly ash engineering properties, mixtures of five different soil types, ranging from ML to CH, and several different fly ash sources (including hydrated and conditioned fly ashes) were evaluated.
Author: David J. White (Ph. D.)
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 76
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To provide insight into subgrade non-uniformity and its effects on pavement performance, this study investigated the influence of non-uniform subgrade support on pavement responses (stress and deflection) that affect pavement performance. Several reconstructed PCC pavement projects in Iowa were studied to document and evaluate the influence of subgrade/subbase non-uniformity on pavement performance. In situ field tests were performed at 12 sites to determine the subgrade/subbase engineering properties and develop a database of engineering parameter values for statistical and numerical analysis. Results of stiffness, moisture and density, strength, and soil classification were used to determine the spatial variability of a given property. Natural subgrade soils, fly ash-stabilized subgrade, reclaimed hydrated fly ash subbase, and granular subbase were studied. The influence of the spatial variability of subgrade/subbase on pavement performance was then evaluated by modeling the elastic properties of the pavement and subgrade using the ISLAB2000 finite element analysis program. A major conclusion from this study is that non-uniform subgrade/subbase stiffness increases localized deflections and causes principal stress concentrations in the pavement, which can lead to fatigue cracking and other types of pavement distresses. Field data show that hydrated fly ash, self-cementing fly ash-stabilized subgrade, and granular subbases exhibit lower variability than natural subgrade soils. Pavement life should be increased through the use of more uniform subgrade support. Subgrade/subbase construction in the future should consider uniformity as a key to long-term pavement performance.
Author: David J. White
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 75
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Book Description
To provide insight into subgrade non-uniformity and its effects on pavement performance, this study investigated the influence of non-uniform subgrade support on pavement responses (stress and deflection) that affect pavement performance. Several reconstructed PCC pavement projects in Iowa were studied to document and evaluate the influence of subgrade/subbase non-uniformity on pavement performance. In situ field tests were performed at 12 sites to determine the subgrade/subbase engineering properties and develop a database of engineering parameter values for statistical and numerical analysis. Results of stiffness, moisture and density, strength, and soil classification were used to determine the spatial variability of a given property. Natural subgrade soils, fly ash-stabilized subgrade, reclaimed hydrated fly ash subbase, and granular subbase were studied. The influence of the spatial variability of subgrade/subbase on pavement performance was then evaluated by modeling the elastic properties of the pavement and subgrade using the ISLAB2000 finite element analysis program. A major conclusion from this study is that non-uniform subgrade/subbase stiffness increases localized deflections and causes principal stress concentrations in the pavement, which can lead to fatigue cracking and other types of pavement distresses. Field data show that hydrated fly ash, self-cementing fly ash-stabilized subgrade, and granular subbases exhibit lower variability than natural subgrade soils. Pavement life should be increased through the use of more uniform subgrade support. Subgrade/subbase construction in the future should consider uniformity as a key to long-term pavement performance.
Author: Tyson David Rupnow
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ISBN:
Category :
Languages : en
Pages : 548
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This thesis contains results from three projects describing self-cementing fly ash stabilization of RAP-soil mixtures, stabilization of limestone screenings for use as a structural layer in road construction, and finite element modeling results of various subgrade materials including self-cementing fly ash stabilized subgrade, natural subgrade, granular subbase, and hydrated fly ash. The first project shows that self-cementing fly ash stabilization of RAP-soil mixtures is economically feasible and structurally capable of supporting construction traffic. The increase stiffness from the addition of self-cementing fly ash increases capacity ensuring long term pavement performance. Addition of self-cementing fly ash increases the consolidated shear strength about five times. The second project shows construction operations and field results proving that stabilization of limestone screenings is viable, cost effective, and produces an adequate structural layer for road construction. The measured moisture-density curves for manufactured sand and limestone screenings are about the same, and the moisture-strength curves show a dramatic decrease in strength beyond the optimum moisture content for strength. Durability testing concluded that CKD stabilized manufactured sand and limestone screenings are not viable construction alternatives, and the addition of class C fly ash with CKD significantly increased the durability of the mixtures. The third project concluded that a link exists between subgrade non-uniformity and pavement performance. Field testing, with the DCP, Clegg Impact Hammer, nuclear density gauge, and GeoGauge, and statistical analysis of subgrade materials concluded that granular subbase, self-cementing fly ash treated subgrade, and HFA decrease the variability of field results. Finite element modeling analysis proved that a link exists between subgrade non-uniformity and pavement performance. Uniform modeling conditions produced lower average deflections and stresses increasing pavement life. Statistical analysis concluded that modeling uniform subgrade conditions produce average stresses that have less variability than those for non-uniform modeling conditions. Pavement response reliability increased with the addition of uniform subgrade, proving that subgrade non-uniformity influences pavement performance.
Author:
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ISBN:
Category : Fly ash
Languages : en
Pages : 182
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Book Description
Soil treated with self-cementing fly ash is increasingly being used in Iowa to stabilize pavement subgrades, but without a complete understanding of the short- and long-term behavior. To develop a broader understanding of fly ash engineering properties, mixtures of five different soil types, ranging from ML to CH, and several different fly ash sources (including hydrated and conditioned fly ashes) were evaluated.
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ISBN:
Category : Portsmouth (N.H.)
Languages : en
Pages :
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Author: David J. White (Ph. D.)
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 171
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Soil treated with self-cementing fly ash is increasingly being used in Iowa to stabilize fine-grained pavement subgrades, but without a complete understanding of the short- and long-term behavior. To develop a broader understanding of fly ash engineering properties, mixtures of five different soil types, ranging from ML to CH, and several different fly ash sources (including hydrated and conditioned fly ashes) were evaluated. Results show that soil compaction characteristics, compressive strength, wet/dry durability, freeze/thaw durability, hydration characteristics, rate of strength gain, and plasticity characteristics are all affected by the addition of fly ash. Specifically, Iowa self-cementing fly ashes are effective at stabilizing fine-grained Iowa soils for earthwork and paving operations; fly ash increases compacted dry density and reduces the optimum moisture content; strength gain in soil-fly ash mixtures depends on cure time and temperature, compaction energy, and compaction delay; sulfur contents can form expansive minerals in soil-fly ash mixtures, which severely reduces the long-term strength and durability; fly ash increases the California bearing ratio of fine-grained soil-fly ash effectively dries wet soils and provides an initial rapid strength gain; fly ash decreases swell potential of expansive soils; soil-fly ash mixtures cured below freezing temperatures and then soaked in water are highly susceptible to slaking and strength loss; soil stabilized with fly ash exhibits increased freeze-thaw durability; soil strength can be increased with the addition of hydrated fly ash and conditioned fly ash, but at higher rates and not as effectively as self-cementing fly ash. Based on the results of this study, three proposed specifications were developed for the use of self-cementing fly ash, hydrated fly ash, and conditioned fly ash. The specifications describe laboratory evaluation, field placement, moisture conditioning, compaction, quality control testing procedures, and basis of payment.
Author: Tuncer Edil
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 130
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Author: Kenneth L. Bergeson
Publisher:
ISBN:
Category : Fills (Earthwork)
Languages : en
Pages : 76
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With the support of the Iowa Fly Ash Affiliates, research on reclaimed fly ash for use as a construction material has been ongoing since 1991. The material exhibits engineering properties similar to those of soft limestone or sandstone and a lightweight aggregate. It is unique in that it is rich in calcium, silica, and aluminum and exhibits pozzolanic properties (i.e. gains strength over time) when used untreated or when a calcium activator is added. Reclaimed Class C fly ashes have been successfully used as a base material on a variety of construction projects in southern and western Iowa. A pavement design guide has been developed with the support of the Iowa Fly Ash Affiliates. Soils in Iowa generally rate fair to poor as subgrade soils for paving projects. This is especially true in the southern quarter of the state and for many areas of eastern and western Iowa. Many of the soil types encountered for highway projects are unsuitable soils under the current Iowa DOT specifications. The bulk of the remaining soils are Class 10 soils. Select soils for use directly under the pavement are often difficult to find on a project, and in many instances are economically unavailable. This was the case for a 4.43-mile grading (STP-S- 90(22)-SE-90) and paving project in Wapello County. The project begins at the Alliant Utilities generating station in Chillicothe, Iowa, and runs west to the Monroe-Wapello county line. This road carries a significant amount of truck traffic hauling coal from the generating station to the Cargill corn processing plant in Eddyville, Iowa. The proposed 10-inch Portland Cement Concrete (PCC) pavement was for construction directly on a Class 10 soil subgrade, which is not a desirable condition if other alternatives are available. Wapello County Engineer Wendell Folkerts supported the use of reclaimed fly ash for a portion of the project. Construction of about three miles of the project was accomplished using 10 inches of reclaimed fly ash as a select fill beneath the PCC slab. The remaining mile was constructed according to the original design to be used as a control section for performance monitoring. The project was graded during the summers of 1998 and 1999. Paving was completed in the fall of 1999. This report presents the results of design considerations and laboratory and field testing results during construction. Recommendations for use of reclaimed fly ash as a select fill are also presented.
Author: Terrel, Epps, and Associates
Publisher:
ISBN:
Category : Pavements
Languages : en
Pages : 172
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