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An experimental investigation was carried out to study the effects of various percentages of fi ne/coarse tire waste and microsilica at various temperatures on the compressive strength of concrete. The compressive strength of concrete mixtures made with tire rubber was assessed statistically with those of concrete containing microsilica and conventional concretes in order to evaluate the usefulness of recycling rubber waste as a component of concrete.Results confi rmed that the recipe and processing temperature of concrete cubes infl uence the compressive strength values. Generally, the use of microsilica or fi ne rubber mixed with microsilica as aggregate replacement of 5% by volume improved the compressive strength of concrete processed at a temperature of 150°C. The addition of coarse rubber did not achieve any increase in strength when used as an aggregate replacement at any percentage. Moreover, the reductions in the compressive strength of concrete mixes at higher temperatures were much smaller for the fi ne rubber with 5 vol% microsilica than those for control and coarse rubber mixes. The specimens made with fi ne rubber and 5 vol% microsilica at elevated temperatures above 400°C appeared to show very similar compressive strength values. The use of fi ne rubber in building construction could help save energy and reduce costs and solve the solid waste disposal problem posed by this type of waste.

Much of the oil spilled into the Kuwait desert during the conflict of 1991 still survives as "oil lakes." Oil spills are usually rapidly degraded by a combination of biodegradation, water washing, evaporation, and oxidation, but because of the low rainfall and lack of near-surface water in the Kuwaiti desert, the first two of these processes cannot operate. Evaporation appears to be the dominant degradation mechanism. We have simulated evaporation of a Kuwait crude oil (from Burgan field) and a Venezuelan crude oil at temperatures of 25, 30, 40, and 50 Њ C and at various air flow rates from 25 to 100 mL/min. Weight loss is initially rapid but subsequently decreases through time. After 30% weight loss the API gravity of the Burgan crude decreased to 22 Њ from an initial value of 30 Њ , and viscosity increased from 65.3 to 300.5 centipoise. Evaporative reduction of oil lake volume and reduced surface area lead to shoreline movement. Applying a cone-shaped model that relates volume loss to distance moved by the shoreline showed that the retreat is much smaller than predicted, implying that the lakes have lost considerably less volume by evaporation than expected. It seems likely that a devolatilized, high-viscosity, high-density, near-surface layer develops, protecting the underlying oil and decreasing the overall rate of evaporation.

The oil lakes in southern Kuwait have accumulated oil that was spilled during the 1991 hostilities and have been exposed to processes of surface degradation for the last decade. Long‐chain normal alkanes are abundant in these oils, showing that biodegradation has not been a major factor, whereas the absence of most compounds with less than 10 carbon atoms suggests a significant role for evaporation. Evaporation has been simulated in laboratory experiments at 25, 30, 40, and 50°C and compositional changes monitored by taking samples periodically for gas chromatographic analysis. Evaporation is initially rapid but slows through time, and ultimately, most compounds with less than 10 carbon atoms are lost. For a given carbon number, loss proceeds in the sequence: normal alkanes> branched chains> aromatics (which is the opposite of water washing). GCMS data for hopane and sterane biomarkers confirm that oil in the lakes is derived from the giant Burgan oilfield and also show that these biomarkers are not affected by evaporation in either nature or the laboratory. Analysis of sulfur compounds using GC‐FPD showed that oils exposed in the lakes were photo‐oxidized and had reduced concentrations of benzothiophenes and increased volatile sulfur compounds. A loss of volatile hydrocarbons from the free surface leads to compositional layering unless the oil is well mixed by convection or diffusion. In experiments to monitor the development of layering, low molecular weight compounds were rapidly lost from the surface, and a steep compositional gradient developed. The formation of a devolatilized, viscous surface “skin” tends to make evaporation a self‐limiting process and also has significance for the design of sampling protocols in environmental forensics.

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