Investigation of mixing ratio and restraint condition effects on alkali-silica gel pressure in mortar by using a uniaxial alkali-silica gel pressure measuring device (ASGPM-D)

Binal A.

CONSTRUCTION AND BUILDING MATERIALS, vol.21, no.6, pp.1218-1228, 2007 (SCI-Expanded) identifier identifier


Alkali-silica reaction occurs when reactive silica in aggregates chemically reacts with alkaline components of cement, forming alkalisilica gel that has harmful effects on concrete because of high swelling capacity and internal pressure. In this study, alkali-silica gel pressure measuring (ASGPM) tests were carried out on specimens comprising opal, chert, chalcedony, andesite, greywacke, basalt, ignimbrite, granodiorite and quartzite aggregates obtained from field or open quarries of Turkey for examination of effects of reactive aggregate types on pressure measurements. The highest alkali-silica gel pressure was measured on cylindrical mortar that included opal (2.81 MPa), the lowest on mortar containing quartzite (0.26 MPa). The rate of alkali-silica gel pressure development was calculated by dividing the pressure values by duration of the experiment. By using these rate values, a new deleterious–innocuous aggregate decision chart was suggested. Furthermore, this decision chart’s classification was compared with ASTM C 289 chemical method, ASTM C 227 mortar bar test, and ASTM C 1260 accelerated mortar bar test method.

A pressure of alkali silica gel which is the product of alkali-silica reaction causes pattern crack development and ultimately failure in cement based materials. This paper examines the measurement of alkali-silica gel pressure in cylindrical mortar specimen by a new test device (alkali-silica gel pressure measuring device, ASGPM-D) and investigates also the effects of the test medium on test results. Specimens of various sizes and geometries were tested to develop standard specimen size for ASGPM test method. The most suitable specimen with diameter of 35 turn and 250 turn in length was selected by optimizing the experimental results. Furthermore, the highest alkali-silica pressure value was recorded on a specimen which has 0.45 w/c and 74-150 mu m grain size in an 80 degrees C 1 N NaOH solution. Also, swelling pressures of four reactive aggregates (opal, chert, basalt and chalcedony) were determined under two distinct restraint stages (1.5 kN and 3 kN). (c) 2006 Elsevier Ltd. All rights reserved.