Ali Soleimanbeigi

Evaluation of Fly Ash Stabilization of Recycled Asphalt Shingles for Use in Structural Fills

The majority of tear-off roofing shingles and manufacturing shingle scraps are currently disposed of as solid waste in landfills. Landfills are also the end place for the majority of coal combustion byproducts like fly ash. In this study, geotechnical properties of recycled asphalt shingles (RAS) stabilized with a self-cementing fly ash (FA) for use as structural fill material were systematically evaluated. Com- paction, hydraulic conductivity, compressibility, shear strength, and coefficient of lateral earth pressure at rest (Ko) of stabilized RAS were evaluated. The maximum dry unit weight (γdmax) of RAS:FA mixtures varies between 11.3 kN=m 3 and 13.8 kN=m 3 qualifying them as light- weight fill material and the compaction curves are not sensitive to water content. The hydraulic conductivity of RAS:FA varies between 2 × 10 −4 cm=s and 3 × 10 −5 cm=s for FA content varying between 0% and 20% resulting in a largely drainable material. RAS has a friction angle (φ 0 ) of 36° and cohesion (c 0 ) of 24 kPa. Addition of 20% FA reduces the φ 0 to 33° but increases the c 0 to 100 kPa making it sufficiently strong as a fill material. However, compared to compacted sand, RAS is highly compressible. Stabilizing RAS with more than 10% of FA, keeps the long-term settlement of a typical highway embankment below the typical settlement limit. Stabilized RAS has a Ko below 0.1 indicating lower lateral pressures behind retaining walls compared to typical soils. Overall results indicate that RAS stabilized with FA has potential as a lightweight material for use as highway embankment fill or retaining wall backfill. DOI: 10.1061/(ASCE)MT.1943-5533 .0000558.

Climatic effect on resilient modulus of recycled unbound aggregates

The effect of temperature on plastic strain and resilient modulus (MR) of different sources of recycled asphalt pavement (RAP) and recycled concrete aggregate (RCA) was evaluated from the results of laboratory temperature-controlled MR tests, with a conventional Class 5 aggregate serving as the control. Freeze–thaw tests were also conducted on samples of RAP and RCA. Five years (spring–summer–fall–winter) of field falling weight deflectometer (FWD) tests were conducted on three pavement sections with RAP, RCA, and Class 5 as the unbound base course. Laboratory test results showed that temperature rise increased plastic strain and reduced MR of RAP under cyclic loads but had a negligible effect on plastic strain and MR of RCA. Freeze–thaw cycles steadily reduced the MR of RAP; however, long-term freeze–thaw cycles increased the MR of RCA. Thermal preloading reduced the plastic strain and increased the MR of the compacted RAP. Construction of a pavement system made with RAP is thus recommended during warm seasons to induce thermal preloading. The elastic modulus back-calculated from the FWD tests did not show a consistent trend with respect to temperature change. No significant change on elastic modulus of RAP, RCA, and Class 5 aggregates due to freeze–thaw cycles was observed over five years.

Compressibility of Recycled Materials for Use As Highway Embankment Fill

AbstractCompressibility of recycled materials including bottom ash (BA), foundry slag (FSG), foundry sand (FSD), recycled asphalt pavement (RAP), recycled pavement material (RPM), recycled concrete aggregate (RCA), and recycled asphalt shingle (RAS) mixed with glacial outwash sand (GOS) was evaluated using one-dimensional (1D) compression tests. Results showed that except RCA, compressibility of all the compacted recycled materials is higher than that of the compacted GOS. Different compression mechanisms were attributed to each recycled material depending on the type, composition, and morphological characteristics of the particles. Bituminous recycled materials including RAP, RPM, and RAS-GOS mixtures exhibited relatively higher compressibility compared with nonbituminous recycled materials. At a constant vertical effective stress (σv′), compression of the recycled materials increased over time with strain rates that are higher for bituminous recycled materials compared to nonbituminous recycled material...

Effect of Temperature on Geotechnical Properties of Recycled Asphalt Shingle Mixtures

Abstract Shear strength, compressibility, and hydraulic conductivity of recycled asphalt shingles (RASs) mixed with bottom ash (BA) or stabilized with self-cementing fly ash (FA) were evaluated in a systematic manner at temperatures ranging from 5 to 35°C, representing seasonal field temperature variation. Increasing temperature reduced the shear strength and increased the compressibility and hydraulic conductivity of compacted RAS-BA and RAS-FA mixtures. When the temperature increased from 5 to 35°C, the effective friction angle ( ϕ ′ ) of the compacted RAS-BA mixture containing 25% RAS decreased from 41 to 35°. The mixture containing 50% RASs decreased from 41 to 29°. The ϕ ′ of the compacted RAS-FA mixture containing 20% FA decreased from 46 to 26°; however, the effective cohesion ( c ′ ) increased from 45 to 70 kPa, and the compressive strength remained higher than that of compacted sand. In contrast, the secondary compression ratio ( C α e ) increased with temperature. The C α e of the RAS-BA mixture...

EFFECT OF TEMPERATURE ON SHEAR STRENGTH OF RECYCLED ASPHALT SHINGLES

The effect of seasonal variations in field temperature on the shear strength of recycled asphalt shingles (RAS) improved by mixing with bottom ash (BA) was evaluated for their use as structural fill material in highway embankments. Typical field temperatures ranging from 5°C to 35°C were induced to compacted mixtures of RAS:BA. An increase in temperature reduced the shear strength of compacted mixtures of RAS:BA, and therefore temperature effects should be taken into consideration in design. The friction angle of compacted RAS:BA mixtures, however, remained within the range suitable for stability of embankment fills. Thermal cycling induced thermal preloading to the mixtures containing RAS; this preloading in turn increased shear strength. From these results, to achieve optimum engineering behavior, construction of highway embankments made with granular materials containing RAS is recommended during warm seasons. The use of RAS in high-volume structural fill applications can contribute to more sustainable roadway infrastructure.

Thermal Conditioning to Improve Geotechnical Properties of Recycled Asphalt Pavements

A procedure for thermal conditioning was introduced to accelerate the compression and improve geotechnical properties of recycled asphalt pavements (RAP) including resilient modulus, compressibility, shear strength, and creep response. Temperature-controlled resilient modulus, one-dimensional compression, and triaxial compression tests were conducted to evaluate the use of RAP as base course or embankment fill. For base course application, increasing temperature increased the plastic strain and reduced the resilient modulus of the RAP specimens that were compacted at room temperature. However, when the specimens were compacted at elevated temperatures and tested at room temperature, significant reduction in plastic strain and increase in resilient modulus were attained. For embankment fill applications, compaction and compression at elevated temperatures increased the shear strength and reduced the compressibility and creep strain of the RAP specimens tested at room temperature. Compaction and compression of the RAP specimens at elevated temperatures induced thermal conditioning and improved geotechnical properties. To improve performance of structural fills containing RAP, construction is recommended during warmest months of the year.

Effects of Curing Time and Fly Ash Content on Properties of Stabilized Dredged Material

AbstractProperties of raw dredged material (RDM) stabilized with self-cementing Class C fly ash (FA) were evaluated for beneficial use in geotechnical construction applications. Emphasis was placed...

Geotechnical and Leaching Properties of Municipal Solid Waste Incineration Fly Ash for Use as Embankment Fill Material

The beneficial use of municipal solid waste incineration (MSWI) fly ash promotes sustainability in highway construction. This study investigated the geotechnical and chemical leaching characteristics of fresh and aged MSWI fly ash samples for use of the material in highway construction applications. The results show that the geotechnical properties of MSWI fly ash resemble those of silty sands with poor drainage capacity. Compared with fresh ash (<10 days since placement), aged ash (3 to 6 months) has a higher California bearing ratio, higher unconfined compressive strength, and greater freeze–thaw durability. The concentrations of cadmium, chromium, selenium, silver, and sulfate from water leach tests are below the limits stipulated in Wisconsin NR 538. The concentrations of heavy metals in leachate from Synthetic Precipitation Leaching Procedure tests are below the U.S. Environmental Protection Agency’s standard maximum contaminant level, with the exception of arsenic. Cumulative mass release from column leach tests indicates that fresh ash will release more heavy metals than aged ash during long-term leaching processes. According to the geotechnical and environmental test results in this investigation, aged MSWI fly ash is identified as a viable material for potential use in roadway construction.

Effects of Temperature on Creep Behavior of Compacted Recycled Asphalt Pavement

AbstractRecycled asphalt pavement (RAP) can be beneficially used as alternative construction material in geotechnical applications, but characterizing its creep response is important to account for...

Compression Behavior of Foundry Sands

Beneficial use and recycling of industrial byproducts promotes sustainability in roadway construction. An estimated 15 million tons of waste sands are produced from foundry operations (e.g., casting) in the US annually, out of which less than 28% is recycled and the remainder is landfilled. High-volume structural fill applications such as highway embankments can possibly use the majority of the foundry sands. One of the primary impediments to beneficial reuse of foundry sand in large volumes, however, is uncertainty with respect to its material and engineering properties, including compressibility and volume change. Foundry sand with bentonite binder may exhibit excessive permanent deformations under long-term loading. Compressibility of foundry sands from five different sources in Wisconsin were evaluated in a systematic suite of one-dimensional (1D) and three-dimensional (3D) compression tests. Compacted foundry sands are more compressible than compacted natural sands. Compressibility of foundry sand increases with bentonite fraction and the rate of secondary compression ratio increases with time. Compressibility parameters for foundry were quantified based on bentonite content. Recommended parameters can be used in numerical analyses to estimate creep deformations of embankments constructed with foundry sands at different stress levels, bentonite content, and time