LABORATORY ASSESSMENT OF CAPILLARY RISE IN STABILISED PAVEMENT MATERIALS

This paper presented the results of standard capillary rise tests, which were carried out on two road building materials (crushed basaltic rocks and scoria) that were stabilized with up to 6% of a number of cementitious additives (GP Cement, GB cement and Alkali Activated Slag). Test results indicated that capillary rise up to the entire specimen height (100%) occurred for both materials, except for the crushed basaltic rocks stabilized with 6% binder content. The rate of rise and the water absorption reduced as the binder content was increased and a similar trend was indicative from 7 days cured to 28 days cured specimens. On the basis of the test performed, it is difficult to draw firm conclusions in relation to the comparative performance of the three binders used. The theoretical basis for the capillary rise was explained using the simple capillary tube model. It was argued that saturated hydraulic conductivity of the stabilized material decreased with increasing binder content, which led to a reduction of the rate and, eventually, the amount of capillary rise. The potential problems associated with the use of capillary rise test results to assess field performance were briefly discussed. On the basis of the theoretical basis presented, it was argued that the test is directly relevant to the field scenario where free water is available at the base (or higher than the base) of the pavement.