X-Ray Microtomography Studies of Air-Void Instability and Growth During Drying of Tile Adhesive Mortars.
X-Ray Microtomography Studies of Air-Void Instability
and Growth During Drying of Tile Adhesive Mortars.
Bentz, D. P.; Haecker, C. J.
NISTIR 7532; 40 p. November 2008.
mortar; adhesives; drying; tile; x ray microtomography;
cements; equations; viscosity; voids; experiments;
A previous X-ray absorption study of tile adhesive
mortars identified a new phenomenon during drying,
namely the movement of small cement particles from the
interior of the specimen to its surface. An analysis
based on Stokes equation indicated that this particle
movement is consistent with the very high viscosity of
these tile adhesive mortars. In addition to this
particle movement, the concurrent formation/growth of
large scale flaws (voids) within the specimens was
observed. The goal of the present study was to observe
this void instability and growth in real time by using
three-dimensional X-ray microtomography. Mitigation
strategies for avoiding the formation of these flaws
were also investigated. Successful mitigation strategies
included the utilization of a coarser cement (larger
particles that do not move during drying), the addition
of an accelerator (to achieve set before flaw formation
can occur), and the addition of a co-thickener (to form
a polymer network to prevent particle movement).
Conversely, the addition of an air entrainer in an
attempt to stabilize the existing air voids was not
successful as a mitigation strategy.