1University of Trinidad and Tobago, O'Meara Industrial Estate, O'Meara, Arima, Trinidad & Tobago, W. I.
2Department of Chemistry, University of the West Indies, St. Augustine, Trinidad & Tobago, W. I.
Asphalt readily deposits on silica gravel aggregate, Tapana aggregate, and the strong interactions have been suggested to create a stable and durable asphalt/aggregate composite. An FTIR single- component analysis was done of the adsorption of oxygen containing model components (ketones, carboxylic acids, dicarboxylic acid anhydrides, 2- quinolone types and sulphoxide) in asphalt (TLA) and bitumen (TPB) on Tapana aggregate and desorption of the same components by bulk water. The thermodynamic parameters derived for adsorption were found to be relatively large; ranging from K = 806 to K = 32468 indicating strong affinity of functional groups for Tapana gravel aggregate. Desorption studies showed that the components with the greatest affinity to the aggregate were the most susceptible to desorption by the added bulk water. The carboxylic acids and sulphoxides moieties demonstrated the highest degree of susceptibility whereas phenolic and the nitrogen based models were least susceptible. The functional group-aggregate interactions were almost invariant to pH changes, however post heat treatment after the initial adsorption is found to partial reduced the per cent of desorbed components. The thermodynamic trends in adsorption or desorption process(es) for the series of functional groups in TLA or TPB provide no definitive reason for the superior durability of TLA over TPB. It is proposed that it is the suspended inorganic kaolinite clay particles in TLA that stabilize the system rather than any specific binding interaction between model components in TLA or TPB.
Trinidad Lake Asphalt, Trinidad Petroleum Bitumen, equilibrium binding constant, functional groups, kaolinite, desorption
