Capillary absorption in concrete and the Lucas-Washbum equation

Capillary absorption kinetics of concrete-ethylene glycol system was studied with respect to concrete matrix porosity and liquid viscosity. Porosity of specimens was altered by air-entraining agents and superplasticizers. Liquid which doesn't react with cement gel was chosen for the experiment in order to study the reasons for deviation from Lucas-Washburn equation observed in concrete-water system. Viscosity of ethylene glycol changes from similar to 23 to 2 mPa s in the temperature range from 20 to 100 degrees C. The values of the capillary coefficient were determined at 20, 60 and 100 degrees C using Neutron Radiography and were found to be in the range from similar to 1.5 to 4.9 MM h(-1/2). The results show that the Lucas-Washburn equation in concrete-ethylene glycol system is valid only for similar to 25 h, which indicates that swelling and rehydration of cement gel are not the main reasons for deviation observed in concrete-water system. (C) 2009 Elsevier Ltd. All rights reserved