Naji Khoury

This study focused on the durability characteristics and moisture susceptibility of a porous plastic-based cementitious material (P-PBC) that is manufactured from plastic waste (PET), soil and aggregates. Use of this material will reduce storm water runoff and provide a pavement structure suitable for walkways, parking lots, recreational courts and other applications. It will also play a crucial role in current recycling programs by diverting large quantities of plastic from landfills and incinerators. P-PBC specimens were prepared in a two step procedure: (1) melting the PET flakes and mixing them with the soil at the melting temperature of plastic until a uniform mixture was attained and (2) thoroughly mixing the PET-soil mixture with the aggregates until uniformity was obtained. Specimens had a plastic to soil ratio (PSR), by weight of 0.75 and a plastic to aggregate ratio (PAR), by weight of 0.175. After compaction, prismatic specimens were cured for 24 hours and tested for freezethaw durability in accordance with the ASTM C666 test method. Results showed that the dynamic modulus of elasticity and modulus of rupture of the specimens decreased as the number of freeze-thaw cycles increased; in addition, moisture susceptibility tests were run according to the AASHTO T-283-89 test method. Results showed that the average tensile strength ratio of P-PBC specimens was greater than 70%, which indicated that P-PBC specimens were not susceptible to moisture.

This study assessed the unclogged hydraulic conductivity, clogged hydraulic conductivity, and contaminant removal potential of a porous plastic based cementitious material (P-PBC). P-PBC was prepared by melting plastic flakes and mixing them with soil and aggregates. Unclogged and clogged hydraulic conductivity were determined utilizing the falling-head approach. Bentonite clay was used as the clogging mechanism. Contaminant removal tests were conducted by passing simulated stormwater runoff containing dissolved cadmium, copper, lead, and zinc through the specimens. An Atomic Absorption Spectrophotometer (AAS) was used to determine the influent and effluent contaminant concentrations. The mix designs utilized a constant plastic to soil mass ratio (PSR) of 0.75 and plastic to aggregate mass ratios (PAR) of 0.10, 0.15, and 0.175. A pervious concrete mix with a water to cement ratio of 0.37; an aggregate to cement ratio of 4:1 was used as a control benchmark. More than forty specimens were prepared, tested, and analyzed. The data showed an inverse relationship between hydraulic conductivity and PAR. Contaminant removal occurred primarily by adsorption, where effluent contaminant concentration typically was decreased. P-PBC pavement not only has the potential to improve water quality and provide an excellent solution to the economic and environmental issues caused by urban stormwater runoff, it also utilizes recyclables that would otherwise end up in landfills.

This study focused on the manufacture, hydraulic and mechanical properties of a porous plastic-based cementitious (P-PBC) material. P-PBC, produced from plastic waste, soil and aggregates, will offer an effective technique for reducing stormwater runoff, improving water quality and providing a structural pavement suitable for pedestrian and vehicular loadings. It will also help divert a large amount of plastic from landfills and incinerators thus playing a crucial role in the recycling efforts currently underway. P-PBC specimens with different plastic to soil/aggregate ratios were prepared and then tested for hydraulic conductivity (k) and indirect tensile strength (ITS). Results showed that k and ITS values of specimens were within the expected values found in the literature for porous pavements. It was also found that the k values decreased with the increase of percentage of plastic waste. ITS, on the other hand, increased with the amount of plastic waste. The study findings indicated that P-PBC could be an effective Stormwater Best Management Practice with significant positive economic and ecological implications.

This study focused on the consolidation characteristics of two soils stabilized with class C fly ash (CFA), lime and plastic waste. Three groups of specimens were prepared: the first group consisted of specimens prepared with 10% class C fly ash and 6% lime and then cured for 28 days; the second set of specimens was prepared with recycled plastic waste with a plastic to soil ratio (PSR) of one; and the last group consisted of specimens prepared with raw soils and compacted at near optimum moisture content and maximum dry unit weight. The last group was considered a baseline to assess the effect of CFA, lime and plastic waste on the consolidation characteristics. Results showed that CFA, lime and plastic waste stabilization reduced the compressibility of soil. In addition, both the compression index (C_c) and swelling index (C_s) decreased due to CFA, lime and plastic waste stabilization. The percentage changes in C_c and C_s varied with the type of stabilizing agents.

SUMMARY: Durability is a notion that is integrated with the performance of stabilized pavement materials. Also, because it can be quantified and measured, it carries significant influence on the design of pavements. This study focuses on using support vector machine, a machine learning algorithm, in assessing the performance of stabilized aggregate bases subject to wet–dry cycles. Support Vector Regression (SVR) is a statistical learning algorithm that is applied to regression problems and is gaining popularity in pavement and geotechnical engineering. In our study, SVR was shown to be superior to the least‐squares (LS) method. Results of this study show that SVR significantly reduces the mean‐squared error (MSE) and improves the coefficient of determination (R²) compared to the widely used LS method. Copyright © 2011 John Wiley & Sons, Ltd.

A laboratory study was undertaken to evaluate the effectiveness of different percentages of hydrated lime, class C fly ash (CFA), and cement kiln dust (CKD) as soil stabilizers. Cylindrical specimens were compacted and cured for 28 days in a humidity room having a constant temperature and controlled humidity. At the end of the curing period, specimens were tested for resilient modulus ( Mr ) , modulus of elasticity ( ME ) , and moisture susceptibility using tube suction test. The study revealed that the values of Mr , ME , and unconfined compressive strength (UCS) for the stabilized specimens increased with the increase in the amount of the stabilizing agent. It was also found that the increase in Mr , ME , and UCS values varies with the type of stabilizing agents. The CKD-stabilized specimens exhibited a higher increase in Mr , ME , and UCS values than the corresponding values of lime- and CFA-stabilized specimens. Additionally, CKD-stabilized specimens exhibited the least moisture susceptibility in term...

A laboratory study was undertaken to investigate the effect of wet-dry (W-D) cycles on aggregate bases, namely, Meridian (M), Richard Spur (RS), and Sawyer (S), stabilized with cement kiln dust (CKD), class C fly ash (CFA), and fluidized bed ash (FBA). Cylindrical specimens were molded, cured, and subjected to W-D cycles prior to testing for resilient modulus (M_r). It was found that the M_r values for most of specimens decreased as W-D cycles increased. Sawyer aggregates stabilized with CKD, however, exhibited an increase with W-D cycles up to 8, beyond which a decrease in M_r occurred. It is believed that such a decrease/increase in M_r values may be attributed to the deceleration/acceleration of pozzolanic reactions. Laboratory observations revealed visual degradation of only Sawyer specimens stabilized with fluidized bed ash after 16 W-D cycles; no M_r tests were performed on the degraded specimens.