Physico -mechanical Properties of High strength Portland cement under the
Influence of different Additives
Noor-ul-Amin
noorulamin_xyz@yahoo.com
Department of Chemistry, Abdul Wali Khan University Mardan, Pakistan
Abstract
In this investigation physico-mechanical properties of high strength Portland
cement have been studied with two additives namely methylmethacrylate and
ethylenediamine, which includes bulk density, cold crushing strength and hydration
behavior. Different doses (1, 2, 3, 4 and 5%) of methylmethacrylate C5H9O2 and
ethylenediamine (C2N2H8) were added to high strength Portland cement. The results
indicated that methylmethacrylate has a negative effect on bulk density, cold crushing
strength and hydration properties, however when present in limited content (not more
than 2 %) its negative effect is relatively slight. On the other hand ethylenediamine up to
3% shows a remarkable increase in the above properties.
Key words: cement, additives, hydration, consistency.
________________________________________________________________________
Address of the corresponding author: Dr. Noor-ul-Amin Assistant professor of chemistry.
PO Box No. 23570. Contact +92-3459493163, E.mail: noorulamin_xyz@yahoo.com,
noorulamin_xyz@live.com
Introduction
Different types of additives have been reported by different authors [Elert et. al
(2008), Saccani and Motori (2006), Zofia et al (2007), Hewlett et al (1998)], which
include lignosulphonates, carboxylic acids, hydroxyl carboxylic acids, hydroxides of
alkali or alkaline earth metals, different types of ammines, polymers etc. All of the
mentioned additives have different functions the most common include grinding aids,
water-reducing
admixtures,
set-retarding
admixtures,
setting
and/or
hardening
accelerators, air entraining admixtures, corrosion inhibitors, plasticizer and super
plasticizer admixtures [Ohama (1997), Ohama (1998), Saki and Sugita (1995), Schultz
(1999), Sakai and Sugita (1995)]. Out of all the known additives, the use of organic
additives is more common in cement chemistry with keeping or improving its strength,
adherence, thermal and acoustical insulation, ductility, fire performance and viscous
damping
For improving the mechanical properties of concrete, resistance to welds
environment deterioration, chemical attack and moistures, polymeric concrete admixture
are usually used, the impact of which depends on the nature and concentration of the used
additives [Larbi and Bijin (1990), Xuli and Chung (1996), Niazi and Jalili (2008)]. The
examples of some of the polymeric compounds are polymer latex, redispersible polymer
powder, water-soluble polymer or liquid polymer. The change in the physical state of
cement paste containing any of the above mentioned additives is accompanied by a
change in water content value and ionic concentration within the paste; this is reflected
on a change of all other properties of the hardened cement paste.
The objective of this work is to study different physico-mechanical properties of
high
strength
Portland
cement
under
the
influence
of
different
doses
of
methylmethacrylate (CH2CHCH3COOCH3) and ethylenediamine (NH2CH2CH2NH2) as
additives to get improved properties.
Materials and methods
High strength Portland cement meeting Pakistan standard specification PS-232
was used in this investigation. Different dosages of additive (1, 2, 3, 4 and 5 % of the dry
cement
weight)
of
two
organic
polymers
namely;
methylmethacrylate
and
ethylenediamine were used.
Several cement batches were used separately to prepare different cement pastes
containing 0 % (blank), 1, 2, 3, 4, and 5 % of methylmethacrylate and ethylenediamine.
In each time the water of consistency was tested. The pastes were separately molded in a
cylindrical plastic moulds, each was 5 cm in diameter and 15cm in length. The molded
cement pastes were kept for 24 hours in a humidity cupboard and were then demolded
and kept in water tank until time of investigations. Three representative samples were
taken from each hardened cement batch for each test at different curing times (3, 7 and 28
days) and tested for their bulk density according to the International standard
specifications. After testing the same samples were subjected to cold crushing strength
test using a machine of maximum load 20000 kg. The obtained load readings were
divided on the surface area of the mould to obtain the cold crushing strength per each
square centimeter. The 28-days hydrated samples were investigated using IR spectra
technique.
Results and Discussion
Bulk density
Fig (1 and 2) shows the results of bulk density at different curing time, using
methylmethacrylate and ethylenediamine respectively. Fig 1 shows that the bulk density
decreases on using methylmethacrylate, the decrease is relatively limited with doses of up
to 2 %, beyond which a great decrease in bulk density is observed. On using
ethylenediamine a noticeable increase in bulk density is observed, this is more obvious
with doses up to 3 %, beyond which (4 and 5 %) the increase in bulk density becomes
less pronounced. On increasing the hydration with ethylenediamine additives, the formed
hydrated products of cements, according to the following equations, fill the pores and
results in higher densities. With methylmethacrylate the relatively lower densities are
correlated with the higher content of mixing water, on hardening this water evaporates
leaving large contents of pores which decrease the density [Niazi and Jalili (2008)].
C2S+xH2O→ C2S.xH2O
C3S + xH2O→ C2S. (X-1)H2O+ Ca (OH)2
C4AF + x H2O→ C3A.6H2O+ CF.(x-6)H2O
Cold Crushing Strength
The cold crushing strength results of 28-days cured cement pastes with
methylmethacrylate and ethylenediamine is shown in Fig (3 and 4) respectively. Fig 1
shows a slight decrease in cold crushing strength values with using up to 2 %
methylmethacrylate, above which a great deterioration in strength is observed. In contrast
to methylmethacrylate, the addition of ethylenediamine results in a remarkable
improvement in cold crushing strength up to 3 %, above which the improvement in
strength is less pronounced (Fig 4). The cold crushing strength behavior is reflected from
the hydration behavior (combined water), i.e., The progress in hydration behavior while
using ethylenediamine results in a considerable increase in mechanical properties while
the slow hydration in case of ethylenediamine addition results in relatively lower cold
crushing strength values.
IR spectra of hydrated cement
Fig 5 (a, b and c) shows IR spectrum patterns of the 28-days hydrated cements in
the absence as well as in the presence of methylmethacrylate and ethylenediamine
additives respectively. The figure shows that the transmittance of IR spectrum patterns of
the hydrated cement in the presence of either methylmethacrylate and ethylenediamine
additives have been decreased to about half of their quantity in absence of additives, This
means that the active sinters (functional groups) of the cement are affected by the
additives, which results in the retardation of hydration in case of methylmethacrylate. In
case of ethylenediamine additives, the better hydration behavior may be due to the
presence of lone pairs of free electrons on the two nitrogen atoms of the molecule that
activate these sinters and hence hydration is promoted.
Conclusion
Based
on
the
above
mentioned
evaluations
it
is
concluded
that
methylmethacrylate has a negative effect on bulk density and mechanical strength.
However it can be used with a dose up to 2 % without a great negative effect. In contrast,
ethylenediamine with a dose up to 3 % results in a noticeable improvement of hydration,
bulk density and mechanical strength. `
References
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London.
Larbi, J.A., Bijin J.M. 1990. Interaction of polymer with Portland cement during
hydration, Cement and Concrete Research, 20:139-147.
Niazi, Y., Jalili, M. 2008. Effect of Portland cement and lime additives on properties of
cold
in-place
recycled
mixtures
with
asphalt
emulsion
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3 days
7days
28days
1.8
1.7
Bulk density
1.6
1.5
1.4
1.3
1.2
1.1
1
Blank
1%
2%
3%
4%
5%
Additive
Figure 1. Effect of Additives on Bulk Density of high strength Portland
cement with Methylmethacrylate
3 days
7days
28days
2
1.95
1.9
Bulk density
1.85
1.8
1.75
1.7
1.65
1.6
1.55
1.5
Blank
1%
2%
3%
4%
5%
Additive
Figure 2. Effect of Additives on Bulk Density of high strength Portland
cement with ethylenediamine
65
Cold crushing (kg/cm2)
60
55
50
45
40
35
30
Blank
1%
2%
3%
Additive
4%
5%
Figure 3. Cold crushing strength of 28 days hydrated cement with
methylmethacrylate
Cold crushing (kg/cm2)
80
75
70
65
60
55
50
Blank
1%
2%
3%
Additive
4%
5%
Figure 4. Cold crushing strength of 28 days hydrated cement with
Ethylenediamine
(a)
(b)
(c)
Figure 5. Infra Red spectra of the 28-days hydrated sample (a). Free cement (b) in
the presence of methylmethacrylate (c) Ethylenediamine additive.