Title:
An Improved Strength Activity Index Test
Author(s):
Prannoy Suraneni
Publication:
Web Session
Volume:
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
4/1/2021
Abstract:
The ASTM C311 strength activity index test is problematic, with inert materials known to pass this test. The early age of testing, low fly ash replacement levels, variable water-to-cementitious materials ratio, and low strength limit all contribute to the inability of the test to successfully distinguish inert and reactive materials. We hypothesize that increasing age of testing, replacement level, and temperature will all aid in better distinguishing inert and reactive materials because they enhance fly ash contribution to strength. Three fly ashes (including a reclaimed ash) and two inert materials (limestone and basaltic fines) were tested to evaluate their performance in several modified strength activity index tests. The results confirm our hypothesis – using 28-day testing age, 50% fly ash replacement level, and 50 °C testing temperature all result in improved variants of the strength activity test, which can clearly distinguish between inert and reactive materials. Results show that bulk resistivity is also able to distinguish between inert and reactive materials with increasing age of testing, replacement level, and temperature. Consideration of an improved strength activity index test or “resistivity index” test in ASTM C618 as a replacement for the current strength activity index test is warranted.