weight. Both mortars had a moisture content of
nol performed even more poorly. However, the
16%. Figure 13 presents the setting times as de-
methanol protected the mortar from permanent
fined in the referenced ASTM standard.
frost damage, allowing full recovery of strength
at 56 days. Since methanol retarded strength gain,
The effect of KC1 on initial and final set of mor-
calcium chloride, a well-known strength-acceler-
tar held at room temperature was insignificant.
At 5C (41F) the KC1 worked better than the
ator, was added to see if the results would
dramatically improve. They did not. The 2% dos-
control mortar where both initial and final set
times were shortened by 4.5 hr. At 5C (23F) the
age of calcium chloride produced strengths that
were somewhat less than those achieved with the
initial and final set times for the KC1 mortar were
methanol alone, and the 4% dosage produced
increased by 10 and 18 hr, respectively, compared
70
Cont+20
60
Cont+5
KC+20
50
KC+5
KC5
40
30
Final
20
10
Initial
0
0
12
24
36
48
Time (hr)
Figure 13. Setting times of admixture-free mortar and mortar containing the ad-
mixture KC1.
with the normal mortar held at 5C. Normal mor-
even lower strengths. Isopropyl alcohol pro-
tar at 5C froze and could not be measured for
duced results similar to methanol. The strength
development of the KC1 mix outperformed the
set time.
other chemicals. It did not retard strength gain,
and it promoted significant strength gain at 5C
Effect of KC1 on freezethaw resistance
and 10C. None of the chemicals evaluated out-
Beam specimens made with type M masonry
cement mortar were freezethaw tested accord-
performed the admixture KC1. Therefore, KC1
was used in the subsequent tests to demonstrate
were tested: a conventional, admixture-free mor-
the feasibility of using in masonry mortars anti-
tar and one that contained 6% KC1 based on
freeze admixtures that were originally developed
cement weight. Both mortars had a moisture con-
for concrete.
tent of 16%. (Though an air-entraining admixture
was not used, a quick examination of the hard-
Setting times
ened mortar with a microscope showed that both
Low temperatures delay the setting times of
mortars contained entrained air bubbles.) The
mortar. This section evaluated the effect of tem-
mechanical condition of each beam prior to and
perature and KC1 on the setting time of mortar.
at intervals during the test was monitored by
The experiment was conducted on a type M
measuring its relative dynamic modulus of elas-
masonry cement mortar according to ASTM C
403, "Test Method for Time of Setting of Concrete
ticity (RDME) according to ASTM C 215. ASTM C
Mixtures by Penetration Resistance." Two mor-
666 considers concrete to be durable if it main-
tars were tested: a normal, admixture-free mortar
tains an RDME above 60% through 300 cycles of
and one that contained 6% KC1 based on cement
freezing and thawing. Since mortar is quite simi-
15
Previous Page
