The potential for scaling of concrete pavement containing fly ash is one of the durability concerns which imposes restrictions on the use of fly ash in paving applications in Indiana during the period of low temperatures (e.g., the late fall construction season). These restrictions increase the cost of paving projects, and occasionally, results in seasonal cement shortages. The objective of this study was to develop a better understanding of the scaling mechanism through a series of laboratory tests that focused on the role of material properties and length and temperature of curing in controlling scaling. Additionally, an attempt was made to simulate field conditions in the laboratory and to relate these results with performance of concrete pavement. Concrete mixtures were prepared with two different slumps using material combinations that had previously shown high susceptibility to scaling. These mixtures were used to study the influence of the length of moist curing and drying periods on scaling of fly ash concrete, exposed to normal and low early-age temperatures. The scaling studies were supplemented with microstructural and chloride ion penetration tests to assist in the interpretation of these results. To study the influence of temperature of curing, fresh properties and scaling were measured for low temperature cast and cured specimens. To understand the behavior of actual pavement constructed in late fall, large size insulated specimens were prepared at low temperature in the laboratory, for scaling and other relevant studies. In relating laboratory scaling results to field performance, wide differences have been observed indicating severity of laboratory scaling test (ASTM C672). Extensive literature review and telephone survey was conducted to collect information regarding field scaling performance of pavements with supplementary cementitious materials. Based on above information and further laboratory studies, five main parameters are suggested to resolve the apparent discrepancies between laboratory results and field observations. Simultaneously, a risk analysis approach was used to determine the probability of scaling in Indiana. It was determined that probability of initiation of scaling for a typical pavement is only 0.5%. It was further concluded that, for replacement levels 20-25%, fly ash can be used to produce scaling-resistant concrete during late fall paving season for climatic conditions similar to that encountered in Indiana.

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fly ash, slag, scaling resistance, maturity, low temperature paving, freezing and thawing resistance, strength development, late-fall construction, SPR-2475

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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