ISSN: 1945-7545
CODEN: GTJODJ
Published Online: 7 April 2011
Page Count: 10

Performance of a Dynamic Dew Point Method for Moisture Isotherms of Clays

Likos, William J.
Dept. of Civil and Environmental Engineering, Univ. of Missouri, Columbia, MO

Lu, Ning
Engineering Division, Colorado School of Mines, Golden, CO

Wenszel, Wentz
Engineering Division, Colorado School of Mines, Golden, CO

(Received 3 December 2009; accepted 18 February 2011)

Abstract

Laboratory tests were conducted to assess the performance of a dynamic equilibrium method for rapidly measuring water vapor sorption isotherms of clays and clayey soils. Emphasis was placed on quantifying temperature stability, measurement reproducibility, establishing a recommended testing protocol, and comparing dynamically generated isotherms with those obtained using a conventional equilibrium method. Adsorption-desorption loops for water activity (a_w) or relative humidity ranging from 0.03 to 0.95 and containing as many as 140 discrete measurements were obtained using the dynamic method in 12–24 h. Far less intensive sorption isotherms using the equilibrium method required ∼600 h (25 days). Measurement reproducibility was within 6 % of the full-scale range. Water contents measured using the dynamic method at a_w less than 0.60 compared excellently with values measured using the equilibrium system and are within 10 to 15 % of the full-scale range at higher activity. Comparisons between total suction characteristic curves obtained using the dynamic system and the equilibrium system suggest a practical total suction measurement range from about 100 000 to 400 000 kPa for a wide range of clay types.

Keywords:
water vapor, sorption, isotherms, surface area, clay, total suction

Paper ID: GTJ102901
DOI: 10.1520/GTJ102901
ASTM International is a member of CrossRef.