Tímarit Verkfræðingafélags Íslands - 01.10.1959, Blaðsíða 23

TtMARIT VFl 1959
73
Table m
No. Andreasen Surface Area cm2/g Blalne Surface Area cmVg Density Undissolved in 6% HCl, % Absorj 7 days >tion of Dime g 90 days CaO/lOOg poz 180 days zolan 360 days
I 4200 4820 2.75 64.5 5.0 10.0 12.3 14.3
II 7000 7420 2.36 95.7 0.6 1.7 3.7 7.0
III 3580 4250 2.64 60.0 7.5 13.0 15.8 18.1
IV 4320 4420 2.65 93.0 0.6 1.6 . 3.0 5.0
V 2660 1830 2.82 34.6 0.6 1.7 3.0 5.4
VI 3000 3980 2.82 71.5 1.8 6.4 7.0 8.6
VII 3580 3030 2.49 61.0 6.9 10.4 10.4 18.8
VIII 6000 7390 2.42 54.0 7.7 12.0 16.0 20.7
IX 4140 2460 2.35 55.0 7.5 12.1 15.8 19.7
X 8500 9000 2.25 34.0 9.5 13.6 17.0 20.1
XI 2810 3630 2.54 27.5 7.7 11.8 14.2 16.7
XH 2040 1630 2.58 23.0 5.2 7.2 10.2 11.9
XIII 2130 1600 2.61 23.0 7.5 9.0 11.4 13.7
XIV 4030 4000 2.55 36.5 5.2 9.2 11.6 15.1
XV 4030 1990 3.31 38.5 1.2 3.2 4.5 7.8
XVI 99.5 0.1 2.0 2.8 4.9
XVII 99.6 0.3 1.2 2.0 3.9
Sement 3340
2. Surface area determinations are glven in table III.
It is felt that surface area greatly influences the pozzo-
lanic activity.
3. Reduction in alkalinity and silica dissolved is
given in gi-aph I. On this graph the limiting line
Rj + % Sj = 630 is drawn; where Rj = reduction in alka-
linity in mM/1, and Sj = silica dissolved in mM/1. Most
of the pozzolans undir investigation fall above the limiting
line. The moberg samples reveal only slight dissolution
of silica, but on the other hand a very great reduciton
in alkalinity. In the well known graph of Mielenz and
others (7), most of the móberg samples fall in the upper
left hand corner where they seem to have a region of their
own. Reduction in alkalinity exceeding 550 mM/1 is
rare (7), but in the case of most of the moberg samples
it is considerably higher.
4. The amount of lime absorbed or neutralized is
shown in table III. The removal of lime is relatively low
but is yet of the same magintude as for some pozzolans
given by Savage (8).
Graph II and III give the relations of lime depletion
to compressive strenght. These graphs indicate that some
relation may exist between compressive strenght and
depletion of lime.
Graphs IV shows the relation between neutralization
of lime and reductions in alkalinity.
5. Solubility in boiling 5% HCl is given in table III.
This test does not show any apparent relations to others
test methods.
6. Compressive and flexural strenght of the pozzolans
as pr. cent of 28 day strenghts of straight mortals is
shown in graph VII—X. Strength graphs indicate strong
pozzolanic activity for most of the materials and in parti-
cular for the pumice sample. The v/c ratio of the straight
portland cement mortar was 0.6, for 15% replacement
0,7, and for 30% replacement 0.85, except in the case of
pumice were the v/c ratio was slightly higher. This
increase in v/c ratio should lead to ca. 20% and 40%
reduction in strenght respectively, if nothing else was
taken into account.
A number of samples show the recognized retrogress-
ion in strenght (17, 18) at later ages when specimens
are stored in. water.
It is apparent, when comparing strength results for
different pozzolans to the reference samples, that both
flexural and compressive strengths are higher than
should be expected, if no pozzolanic actions were taking
place, particularly for 30% replacement.
7. Free lime determination is given in graph V. This
graph shows a definite removal of lime by the pozzolan
replacements. A correlation between strenght and free
lime is visible from graph VI.
8. The lime-mortar test for pozzolans revealed a
positive result only for sample No. 2. This seems to be
a contradiction to the majority of the other tests. It
should be borne in mind that this test is carried out
at 55 °C whereas the rest of the strenght test were
carried out at room temperature.
A pozzolan may have both physical and chemical