A NEW EXPERIMENTAL METHOD AND DEVICE FOR MEASURING ALKALI SILICA GEL PRESSURE IN MORTAR

摘要

In this study, a new experimental device (Alkali Silica Gel Pressure Measuring Device, ASGPM-D) was designed and a new method (Alkali Silica Gel Pressure Measuring Test, ASGPM Test) was developed to measure the alkali-silica gel pressure and to estimate the damages it causes in the mortar. Experimental results indicated that the most suitable sample geometry to be used in this new experimental method is the one with the diameter of 35 mm and the length of 250 mm, which shows the least lateral expansion and bending. ASGPM tests were applied on cylindrical mortar specimens having different water/cement ratio in order to investigate effects of water/cement ratio on alkali silica gel pressure measurements. Mortar specimens having 35 mm diameter, 250 mm length and 2.25 aggregate/cement ratio and include opal nodules used in tests. At the end of these tests, ultimate alkali silica gel pressures were measured from specimens having 0.45-water/cement ratio and the lowest alkali silica gel pressures were measured from a specimens having 0.3-water/cement ratio. After test standardization studies, alkali silica gel pressures were determined in mortars including opal nodules", chert nodules, chalcedony nodules, basalt, andesite and tuff aggregates for examination of effects of reactive aggregate types on the pressure measurement. The highest alkali silica gel pressure was measured on cylindrical mortar including opal nodules (3.81MPa). On the other hand, the lowest alkali silica gel pressure was measured on mortar containing basalt as potentially reactive aggregate (0.53MPa). The velocity of development of alkali-silica gel pressure was calculated as dividing the pressure values by duration of the experiment. Using these velocity values, a 'chart' was prepared to be use to distinguish 'deleterious' and 'innocuous' aggregates.