THE EFFECT OF STRESS-RELAXATION, SELF-DESICCATION, AND WATER-ABSORPTION ON THE ALKALI-SILICA REACTION IN LOW WATER CEMENT RATIO MORTARS/

A device has been designed and tested for measuring the stress caused by the alkali-silica reaction (ASR) in mortars. Specimens were placed in a frame equipped with a load cell, allowing us to approximately fix the strain at zero and measure the total stress generated over time. The specimens and the frame were immersed in a 1-N NaOH solution at 50 degrees C. Even without ASR, the specimens expanded due to water abso rption that relieves the shrinkage caused by self-desiccation. In addi tion, applied stresses, as well as stresses that were set up in the sa mple by expansion caused by ASR and/or water absorption, were subject to stress relaxation. By using companion samples having nonreactive ag gregates, we were able to distinguish the stress caused by ASR from th at caused by water absorption-driven expansion. The effects of stress relaxation could not be removed without further experimentation and th eoretical analysis. (C) 1997 Elsevier Science Ltd.