Browsing by Subject "Fly ash"
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Item The Effect of Composition on the Alkali-Silica Mitigation Potential of Fly Ash-Ground Glass Blends in Concrete(2019-08) Doolittle, NathanThis research investigates the use of ternary blends of Portland cement, ground glass and four different fly ashes as a mitigation method for alkali-silica reaction (ASR) in concrete. ASR is the reaction between select reactive aggregates and alkalis in the pore solution of concrete added by the hydration of portland cement. The inclusion of fly ash and waste glass has potential to reduce the deleterious expansive effect of ASR. Testing conducted involves measurement of length change, compressive strength and the fresh mix properties.Item Hydraulic and Mechanical Properties of Recycled Materials(Minnesota Department of Transportation, 2009-10) Gupta, Satish; Kang, Dong Hee; Ranaivoson, AndryConstruction and maintenance of roads requires large volume of aggregates for use as base and subbase materials. Because of the cost of virgin aggregates, federal and state agencies are encouraging the recycling of waste materials including materials in old pavements. This study assessed the suitability of four recycled materials relative to virgin aggregates for use as base and subbase materials. The four recycled materials were the reclaimed asphalt pavement (RAP), fly ash (FA), reclaimed concrete material (RCM), and foundry sand (FS). Assessment of these materials was done in terms of their hydraulic, mechanical, and leaching properties when mixed in with various proportions of virgin aggregates. Except for slightly higher fine content in some RAP-aggregate mixtures, particle size distribution of all mixtures was within the Mn/DOT specification band for Class 5 materials. Water retention (pore size distribution), hydraulic conductivity, resilient modulus, and shear strength measurements were generally similar to that of 100% aggregates. Exception was the mixtures of FS. Heavy metal concentrations in the leachate were also generally less than the EPA drinking water standards. We concluded that FA, RAP, and RCM mixtures will be good substitutes of virgin aggregates as base and subbase materials.Item Ravine alluvial fans as records of landscape change in the Le Sueur River Basin, southern Minnesota(2017-10) Treat, IanRavine alluvial fans in the Le Sueur River Basin (LSRB) of south-central Minnesota record post-glacial Holocene changes and modern anthropogenic disturbances to land cover and hydrology in high-latitude watersheds. Seventy meters of base-level drop at the end of the last glaciation initiated millennia of incision that continues on the LSRB today. Onto this template of on-going incision, Euro-American land clearing and drainage of previously stable upland prairie and wetlands in the mid-1800s further increased erosion rates in the basin. Ravines, first-order channels that link low-gradient uplands with the deeply-incised channel network, experienced changes in erosion rates over time from both impacts, with the erosional history preserved in alluvial fans at the mouths of ravines where they terminate on fluvial terraces. Establishing a post-settlement chronology is difficult in the highly erosive knickzone of the Le Sueur. We take advantage of six fan deposits spread throughout the LSRB to determine the fluvial response of upland agricultural land conversion on steep first-order drainages. Ravines respond quickly to sediment and hydrology fluxes in the basin that are reflected in their alluvial fans as packages of post-settlement alluvium (PSA) and incision through fan surfaces. Bulk soil samples collected at 10-, 20-, 40-, 100-, and 200-centimeter depths on the selected fans as well as samples from the incised channel were analyzed for fly ash, spherical silt-sized grains that are a byproduct of coal combustion. The presence of fly ash as an in-situ stratigraphic marker at depth was used to calculate conservative post-settlement deposition rates of 0.93 and 1.67 cm/yr using observation techniques from high-powered transmitted and reflected light microscopes as well as scanning electron microscopy, respectively. These rates are a three-fold increase over generous Holocene deposition rates of 0.27 cm/yr. Incision through fan surfaces also marks post-settlement changes. Trenching and tile drainage on the uplands allowed for greater transport of water down ravines and onto fans. These results confirm land use change triggered an increase in upstream erosion and fan deposition followed by incision on short time scales.