HoughtonlakeBoard.org

TIPS & EXPERT ADVICE ON ESSAYS, PAPERS & COLLEGE APPLICATIONS

2.1. Materials

Portland
cement clinker and gypsum are used as the main components of the cement in the
study. All cement shown in Table 1 are produced from the same batch of clinker
and gypsum in the study. As a grinding aid, triethanolamine (TEA) and
triisopropanolamine (TIPA) are used. In addition, BA and AHBA were used as
boron compounds in which the effects on the performance of grinding aid were
searched. For experiments, precision scales Precisa XB6200D. 5-6200 gr. ±0.1 g
ve Kern BJ-220-4NM. 0-220 g ±0.0001 g, laboratory crusher, laboratory mill,
mortar mixer, Vicat test equipment and mold manual and automatic Atom Teknik ,
deiosined water, lithium tetraborat (66%) for fuse beads of XRF analysis,Fluxana
fusion machine, platinum crucible, mould, and XRF Panalytical Zetium were
used.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

2.2.
Preparation and Experimental Method

The
size of the clinker was reduced (3 mm or less) by passing it through the
laboratory type crusher before the experiments to ensure homogeneity and then
mixed. Portland CEM I type cement was produced in the experiments. In the
experiments, grinding aids were used in all the cement produced except the
reference cement. For each experiment, 3000 g of clinker was weighed and then
the grinding aid + boron compound were added to give a total weight of 0.1% and
the mixture was thoroughly mixed. This mixture was run for 40 min after the
laboratory-type ball mill was loaded. Samples were taken from the stopped mill
and the SO3 level was checked and the gypsum was added to the mill
3.05 ± 0.05% according to the target final level and the mill was run again
for 40 min. Cement samples ground for a total of 80 mins were taken separately
for each experimental set by XRF elemental analysis.

For
the Vicat tests of cement samples, they were subjected to the consistency test
according to TS EN 196-3:2017 23. The cement samples with consistency water
were prepared for the Vicat test according to TS EN 196-3:2017 standard and the
beginning and the final setting times were determined in automatic Vicat
device.

 

3.
Results and Discussion

Setting
time tests with varying grinding aid contents were performed under the constant
laboratory conditions (T:20oC and Relative Humidity>50 %). An
average of three test readings was taken as the final reading. To compare the
changes occurred in setting times by addition of grinding aids, the setting
time of cement paste without grinding aid content was used as a reference. The
setting times were recorded in minutes.

All
of the cement samples produced by using TEA  mixtures are more than 75 minutes which are suitable
for initial setting values as specified in TS EN 197-1: 2012 24. A total of 3
g of material (0.1 wt% cement) is used as grinding aid in each experiment. According
to the cement sample referred in Table 1 and Graph 1, the beginning and final
setting times are higher for the cement sample ground with 100% triethanolamine
according to the reference cement. This demonstrates the a mild retarding
effect of the TEA in hydration reactions which is compatible with Dodson’s 1
and Allahverdi’s studies 15 .

When
the TEA content in the total cement is reduced by the addition of boric acid
instead of 25% TEA, the settings begining and final are very similar to 100%
TEA study (Table 1, Graph 1). By increasing boric acid ratio to 33% where TEA
was used at 67% as grinding aid, initial setting time was faster than
experiments with 100% TEA and 75% TEA + 25% boric acid. The final setting of
this sample was also earlier than the the final setting of samples of 100% TEA
and 75% TEA + boric acid (Table 1, Graph 1). Addition of boric acid showed a
mid accelaration in setting points acording to %100 TEA results which is
contradictory
 to the mentioned results in previous
studies 2,3,9,10,13,15. The mechanism of this
contradictory could be because of a reaction between TEA and boric acid as it is
discussed in Sonoda 21 study. Up to pH level of 10.9 and at low temperatures
these two compound consume each other and make a new complex triethanolamine
borate. So during the pre-induction and dormant period of cement hydration
reactions by adding the boric acid to the system, the TEA-B complexes formed which
reduce the concentration of TEA and boron compounds in the liquid phase. So the
retardation effect of TEA reduced and it is seen in 75% TEA + 25% boric acid
and 66 % TEA + 33% boric acid samples as a reducing retarding effect.

The
typical B2O3 content of boric acid and anhydrous Borax
are 56.5 % and 68.5% respectively. For 25 % boric acid mixture this means
14.13% B2O3 and for 33 % boric acid mixture it means
18.65% B2O3. The B2O3 content of
25% and 33% anhydrous borax are 17.25% and 22.61% respectively. It is
understood from setting points of 75% TEA and 25% anhydrous borax sample that
there occurred a reaction between the TEA and anhydrous borax molecules in an aqueous
solution of cement paste also. Like the mechanism of boric acid the anhydrous
borax molecules and TEA balanced each other and only the remaining grinding aid
mixture which is mostly TEA slightly retard the cement set points (Graph 1).
The initial and final setting points of 66% TEA+ 33% boric acid mixture and 75%
TEA+ 25% anhydrous borax are very similar because the total B2O3
content in the mixtures is also proximate 18.65% and 17.25% respectively. The
mixture of 67% TEA and 33% anhydrous borax has nearly the same setting points
with 25% anhydrous borax containing mixture. 5 minutes retardation may because
of more SO3 content (0,06% more) which can react with C3A.

All
of the cement samples produced using TIPA are compatible with the initial
settings values specified in TS EN 197-1: 2012. A total of 3 g of material (0.1
% weight of cement) was used as grinding aid in each experiment. It is seen in
Table 1 and Graph 2 that the cement sample ground with 100% TIPA has 10 minutes
retarded initial setting and similar final setting according to the reference cement.
Although in literature TIPA behaves as a setting accelerator, it is not seen a
significant change in settings for 100% TIPA used cement sample. For both boric
acid and anhydrous borax mixture experiments no significant change found in
setting points for two different  25% and
33%  mixing ratios. This mainly because
of calcelation of their setting effects.

Post Author: admin

x

Hi!
I'm Irvin!

Would you like to get a custom essay? How about receiving a customized one?

Check it out