This paper presents the results of an experimental program devoted to the study of Polymer Modified Mortars’ (PMM) thermal conductivity, thermal diffusivity and calorific capacity at different temperatures and compressive and flexural strengths at room-temperature. For this purpose, Ordinary Mortar (OM) and PMM samples with different contents and through partial substitution of Portland cement were prepared. A real improvement of the PMM thermal properties was observed in comparison with those of OM despite the decrease of mechanical strength. X-rays Diffract Meter (XDM), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscope (SEM) were also conducted to show the interaction of the polymer material considered.
Trang 1Experimental study on thermo-mechanical properties of Polymer
Modified Mortar
a
Civil Engineering Department, Faculty of Architecture and Civil Engineering, USTO (Mohamed Boudiaf), BP 1505, El Menaouar, 31000 Oran, Algeria
b
Department of Civil Engineering, Laboratory of Materials, ENSET, 31000 Oran, Algeria
c
Faculty of Science, Laboratory of Polymer Chemistry, University of Oran, 31000 Oran, Algeria
a r t i c l e i n f o
Article history:
Received 8 January 2013
Accepted 17 May 2013
Available online 29 May 2013
Keywords:
Poly-Ethylene
Thermal conductivity
Thermal diffusivity
Calorific capacity
Compressive strength
Tensile strength
a b s t r a c t
This paper presents the results of an experimental program devoted to the study of Polymer Modified Mortars’ (PMM) thermal conductivity, thermal diffusivity and calorific capacity at different temperatures and compressive and flexural strengths at room-temperature For this purpose, Ordinary Mortar (OM) and PMM samples with different contents and through partial substitution of Portland cement were pre-pared A real improvement of the PMM thermal properties was observed in comparison with those of OM despite the decrease of mechanical strength X-rays Diffract Meter (XDM), Differential Scanning Calorim-etry (DSC) and Scanning Electron Microscope (SEM) were also conducted to show the interaction of the polymer material considered
Ó 2013 Elsevier Ltd All rights reserved
1 Introduction
Amongst all the materials used in construction, concrete using
Ordinary Portland Cement (OPC) still the most largely used
mate-rial in the world and since the early 18th century, and the second
after water[1] Cement is largely used in the preparation of
con-crete and the demand of this material is in continuous growth to
meet the needs of society in terms of housing and buildings
con-struction The popularity of concrete using OPC can be attributed
to its simplicity in preparation and its easy availability However,
the cost of cement is in continuous growth despite the danger it
causes to public health and environment To cope with this
prob-lem, plastic wastes such as High Density Poly-Ethylene (HDPE)
can be used as partial substitutes to OPC and considered as
sustain-able building material Incorporating polymers in mortar and
con-crete has contributed to propose new structural materials such as
Polymer Modified Mortars (PMMs) and Polymer Modified Concrete
(PMC)[2] Several studies were conducted to describe the potential
of using polymers in the concrete technology The use of PMM and
PMC in specific applications such as damaged concrete, protecting
constructions can, to some extent and by their versatile
applica-tions, contribute to this excessive demand
In the past, researchers used industrial or plastic wastes such as
glass [3] or fiber [4] in the preparation of self-consolidating
concrete Nowadays, the re-use of PET wastes seems to be an appropriate solution in the development of new formulations of building materials such as concrete PET wastes were extensively used in laboratory programs During the last two decades, studies
on the use of PET wastes in concrete technology and construction materials[5]were largely undertaken In line with this research, Albano et al.[6]and Benosman[7]studied the use of PET in com-posite polymers In those studies, Albano investigated the mechan-ical behaviour of recycled concrete using PET and varying W/C ratio (W/C = 0.5 and 0.6) On his side, Benosman added several per-centage of PET by partial substitution to Portland cement He stud-ied the mechanical effects and the durability of modified mortars Many researchers were concerned with industrial products such as silica fume[8–10]and nano-silica[11–13]but others rather stud-ied thermal conductivity and mechanical strength[14–19] Among those researchers, Xing et al.[15]concluded that it is within the ce-ment paste that the main phenomena of dehydration and expul-sion of moisture took place and lead to concrete deterioration They reported that, at high temperatures, the behaviour of con-crete or cement is strongly dependent upon the properties of ce-ment paste
Many experimental programs were conducted on polymers in the world However, none of those studies (to the authors’ knowl-edge) were concerned with thermal conductivity, capacity and dif-fusivity effects on PMM and PMC Also, Algeria is one of the countries in the world in which the quantity of household wastes
is about 8.5 million tons per year (0.75 kg per inhabitant and per 0261-3069/$ - see front matter Ó 2013 Elsevier Ltd All rights reserved.
⇑ Corresponding author Tel.: +213 773886687; fax: +213 41423130.
E-mail address: amel.aattache@univ-usto.dz (A Aattache).
Contents lists available atSciVerse ScienceDirect
Materials and Design
j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / m a t d e s
Trang 2year) and is in continuous increase In the city of Algiers this
reaches 1 kg per inhabitant and per year In Algeria and all over
the world, the use of packed products has induced an increase in
dumped plastic wastes and a difficulty of their removal from
grounds In addition, in this country, polymer materials are hardly
used as construction materials and in both research and
applica-tions of PMM and PMC, Algeria is still far behind most countries
It was therefore an opportunity for the authors to initiate research
in the field of these types of polymer-based concretes
The study presented in this has a two-fold purpose: (i) to study
the thermal and mechanical properties of the different PMM
sam-ples under different temperatures; (ii) to show the interaction of
polymer matrix using X-rays Diffract Meter (XDM), Differential
Scanning Calorimetry (DSC) and Scanning Electron Microscope
(SEM) For both purposes, the Poly-Ethylene used was ground
and partially substituted to Portland cement The behaviour of
PMM samples at various temperatures and the evolution of
ther-mal properties under temperature increase were undertaken and
measurement of conductivity, calorific capacity and thermal
diffu-sivity were performed using the Quickline-30 equipment which is
described below For the mechanical properties of the PMM
sam-ples, compressive and flexural test were also performed at
room-temperature (20 °C)
2 Materials
2.1 Polyethylene
The HDPE used is a powder ground grains type provided by
EQUATE Petrochemical Company (5KSCC) of Koweit with a
diame-ter less than 0.5 mm, as shown inFig 1 It is used for fabrication of
plastic bags The main properties of this HDPE are reported in
Table 1and the Differential Scanning Calorimetry (DSC) is shown
inFig 2
In order to show the degradation of HDPE under the effect of
temperature, DSC analysis is considered DSC analysis is carried
out using a NETZSCH DSC-204F1 apparatus The HDPE sample is
placed in an aluminum crucible and is considered as a reference
to aluminum The values are recorded under a helium atmosphere
and a speed rate of 5 °C/min For this material, the melting point
occurred at 124.9 °C as shown by the endogenous peak onFig 2
One can also see that deterioration begins at 300 °C Also, to
eval-uate the conductivity, capacity and thermal diffusivity, under the
effect of temperature and according to HDPE thermogramme,
tem-peratures of 20 °C, 140 °C, 250 °C and 350 °C were considered
2.2 Adjuvant The blending agent used is AETERNUM-3 superplasticiser com-ing from a TECKNACHEM company in Sidi Belabbes (west of Alge-ria) This adjuvant is mainly made of carbon, silicate and new powder generations infused in active nano-micro silicates This type of adjuvant connects with a high pouzzolanic activity of the nano-micro silicates and assures rheology, fluidity with no segre-gation and permeability 3% of AETERNUM-3 is added to the ce-ment weight This addition allows the preparation of mortars and concretes with reduced W/C ratios The physical and chemical properties of this AETERNUM-3 superplasticiser are reported in Tables 2 and 3, respectively
2.3 Cement Portland cement type (CEM I/42.5) was used for the preparation
of samples This type of cement resists to sulfates and the chemical Fig 1 Photograph of an amount of HDPE passed through a 0.5 mm sieve.
0 50 100 150 200 250 300 350 400 450 500 -2.5
-2 -1.5 -1 -0.5 0 0.5 1
Temperature (°C)
Table 1 Chemical and physical properties of HDPE.
Density at 20 °C (g/cm 3
Thermal conductivity at 23 °C (W m 1
K 1
Trang 3properties of which are given inTable 3 It is provided by the
Fac-tory of Zahana (west of Algeria), according to the Algerian standard
NA442 The Blaine specific surface of cement is 3308 cm2/g
(S = 3308 cm2/g) and the absolute density of anhydrous cement is
3.16 cm3/g (q= 3.16 cm3/g)
2.4 Sand
The material comes from Sobha River (west of Algeria) It is a
standardized according to the EN 196-1 standard and provided
ANADOLU Company mixed to plastic bags of 1350 ± 5 g content
The chemical and physical properties of sand are reported in Tables 3 and 4, respectively
2.5 Polymer Modified Mortar samples Polymer Modified Mortar (PMM) samples, the composition of which is given inTable 5, are prismatic samples according to EN 196-1[21] Each sample is cut into two pieces to carry out analyses
of conductivity, calorific capacity and thermal diffusivity These samples were cast into moulds for 24 h and then kept into water
at 20 °C, up to 7, 14, 28, 90 and 120 days Average results of the samples were considered
2.6 Test equipment The Quickline-30 apparatus is a product of ANTAR CORPORA-TION PITTSBURG, PA (USA), seeFig 3 It is a multi-functional por-table equipment used for measuring surface temperatures, thermal conductivity, heat capacity and thermal diffusivity This equipment uses the principle of the transient heat line method that helps in reducing testing time compared to other methods involving stea-dy-state conditions The conductivity, calorific capacity and ther-mal diffusivity of the sample are measured using a probe which
is equipped with a heating-coil The Quickline-30 equipment uses the standard ASTM: D5930 method for finding thermal conductiv-ity of plastics by means of a transient line-source technique It also uses the ASTM: D5334 standard test method for determining the thermal conductivity of soil and soft rock by a thermal needle probe procedure, as described in Ref [17,20] The measurement time of the Quickline-30 apparatus lies between 16 and 20 min
3 Results and discussions
A total of 5 types of mortars reflecting different compositions were considered In the sequel, the mortars are labeled OM, MA for Ordinary Mortars, Mortar with adjuvant and MA/PE2, MA/PE4 and MA/PE6 for Mortars with Adjuvant using 2%, 4% and 6% of Poly-Ethylene, respectively Samples of 4 4 8 cm3 from each category were considered making a total of 300 samples Thermal conductivity, thermal capacity and thermal diffusivity were mea-sured with a Quickline-30 apparatus All the samples were tested
at room-temperature and at 140 °C, 250 °C and 350 °C with a heat-ing speed of 1 °C/min[15] The temperature of 140 °C corresponds
to the HDPE melting phase in the cement matrix The samples were taken out of the oven after temperature being stabilized After being cooled, the samples were put into a confined dry space to ab-sorb all form of humidity and tested using the Quickline-30 appa-ratus at room-temperature (20 °C)
Table 2
Physical properties of AETERNUM-3 superplasticiser.
Density (g/dm 3
Table 5
Composition of mortars.
Table 4
Physical properties of sand.
Table 3
Chemical properties of cement, sand and superplasticiser.
Chemical properties Cement (%) Sand (%) Superplasticiser (%)
Trang 43.1 Thermal conductivity
Fig 4illustrates the variation of the thermal conductivity of the
OM, MA, MA/PE2, MA/PE4 and MA/PE6 mortars samples and for
the different ages, namely 7, 14, 28, 90 and 120 days Thermal
con-ductivity is the ability of the samples material to conduct heat As
it was already reported in different studies including[22,23], one
can observe that the conductivity decreases when temperature
in-creases for the various ages considered It is worth noting that
vaporisation of free water starts at about 100 °C and is completely
drawn off at 120 °C and the loss of chemically related water took
place between 180 °C and 300 °C, as Calcium Silicate Hydrates
(CSH) start to decompose However, when the water vapor is
to-tally eliminated, thermal conductivity start to decrease with the
increase of temperature Also, when mortars are submitted to
tem-perature increase, the water in the pores is released and the pores
become the entry points for air Therefore, when pores are full of
air rather than water, the mortars are endowed with low
conduc-tivity, as air conductivity is 25 times less than that of water This phenomenon was previously reported by Hanichet[24]
For MA/PE2, MA/PE4 and MA/PE6 samples, thermal conductiv-ity decreased with the HDPE content which evaporates when the temperature increases Anew, this is due to the presence of pores during the elimination of HDPE (seeFig 4).Fig 4a shows that, at room temperature, MA/PE6 samples have the lowest thermal con-ductivity for the different ages when compared with PMM sam-ples Indeed, HDPE has a low thermal conductivity (0.33 W m1K1) The thermal conductivity of MA/PE6 is 6.66% less than that of Ordinary Mortar (OM), MA and PMM mortars (1.51–1.52 W m1K1) The thermal conductivity of OM, MA and PMM mortars stabilises from day 28 to day 120 On the other hand,
MA samples which contain only superplasticiser have a higher con-ductivity in comparison with OM mortar since day 28, as the pores are well distributed within the material and because nano-silicates reduce pores appearance and as nano-particles behave as a filling agent[13]
Fig 3 ISOMET apparatus and its surface lead.
7 14 28 90 120 0
0.5 1 1.5 2
Days
(a)-Temperature 20°C
7 14 28 90 120 0
0.5 1 1.5
Days
(b)-Temperature 140°C
7 14 28 90 120 0
0.2 0.4 0.6 0.8
1
1.2 1.4
Days
(c)-Temperature 250°C
7 14 28 90 120 0
0.2 0.4 0.6 0.8 1
Days
(d)-Temperature 350°C
OM MA MA/PE2 MA/PE4 MA/PE6
Fig 4 Variation of thermal conductivity of mortars with temperature.
Trang 53.2 Calorific capacity
The variation of calorific capacity (qCp) with temperature is
shown inFig 5 Calorific capacity – expressed by the product of
mass heat (J/kg K) and by density (kg/m3) – is defined as the heat
quantity that a material is able to store for a given volume It is also
defined as the necessary heat quantity that increases by 1 °C the
temperature of one cubic meter of material.Fig 5shows that the
calorific capacity decreases with the increase of temperature Yet,
a raise or peak of capacity for MA/PE4 was observed at 140 °C
(seeFig 5b) in comparison with that at 20 °C (see Fig 5a) and
which corresponds to the fusion phase for HDPE material After
cooling, HDPE material recovers its initial state and the calorific
capacity is increased For this material, a very high quantity of
en-ergy is necessary to raise temperature by 1 °C Therefore, the
mor-tar has either stored or received energy in order to have HDPE
melted Unlikely, at room-temperature, the increase of HDPE
con-tent engendered a decrease of thermal conductivity for PMM
sam-ples and a low variation of the calorific capacity The effect of the
calorific capacity was small because of the low HDPE capacity
(0.011106 J/m3K) is counterbalanced by the capacity of water
(4.18106 J/m3K) therefore saturating the pores of the mortar
Mounanga et al.[25]also observed this low variation with
polyure-thane foam However, MA/PE6 mortar has a calorific capacity of
5.55% and 10.52% less than that of OM and MA mortars,
respectively
3.3 Thermal diffusivity
Fig 6shows the thermal diffusivity at different temperatures
Thermal diffusivity represents the speed at which heat spreads
out within the material It is proportional to the specific heat and
density according to the following relation:
where a is the thermal diffusivity in m2/s, k is the thermal conduc-tivity in W/m K,qis density of material in kg/m3and C is the mass heat in J/kg K1
Under the effect of temperature (seeFig 6b–d), thermal diffu-sivity decreases in general As thermal diffudiffu-sivity is proportional
to conductivity, it follows the same decay phenomenon MA/PE6 mortar is endowed with a thermal diffusivity of 3.75%, 14.29% and 7.69% less than that of OM and at 140, 250 and 350 °C, respec-tively MA/PE6 thermal diffusivity is also 9.4%, 11.76% and 4% less than that of MA mortars and for the same temperatures At 20 °C,
OM and PMM mortars depict almost the same behaviour MA/PE6 has a diffusivity of 0.8 106to 0.82 106m2/s One may con-clude that diffusivity is largely dependent on water content in the mortar Therefore, the lower the diffusivity, the longer time is needed for the heat front-line to cross the sample thickness and
to reach the opposite side of the sample
3.4 Thermal conductivity-density relationship There is a straightforward correlation between conductivity and density This explains why porous materials (low density materials) have a low thermal conductivity and why they are often recom-mended for buildings as they insure a good thermal insulation However, they are not very good conductors of heat (cellular con-crete, for example)[26] Therefore, density, thermal capacity and diffusivity are three main heat transfer factors by conduction:
Fig 7shows that thermal conductivity decreases with the de-crease of density For instance, MA/PE6 has the least density in comparison with other mortars due to the incorporation of HDPE
0 0.5 1 1.5 2
Days
(a)-Temperature 20°C
0 0.5 1 1.5 2
Days
(b)-Temperature 140°C
0 0.5 1 1.5 2
Days
(c)-Temperature 250°C
0 0.5 1 1.5 2
Days
(d)-Temperature 350°C
OM MA MA/PE2 MA/PE4 MA/PE6
Fig 5 Variation of calorific capacity of mortars with temperature.
Trang 6(0.94–0.97 g/cm3) Uysal et al.[27]have carried out a comparison
study to explain the influence of cement content on density and
conductivity They reported that density of concrete increases with
the increase of cement content, and when this latter increases
con-ductivity increases Blanco et al.[28]also pointed out that
conduc-tivity decreases because with the decrease of concrete density
3.5 X-rays Diffract Meter
To shed light on the chemical interaction between the cement
material and the HDPE, XDM spectra analysis of OM and MA/PE6
was conducted Both mortars were kept in water for 120 days for
a direct comparison.Fig 8 shows the XDM spectrum of OM For this material, the analysis permitted to conclude that there is no chemical interaction between the cement and the HDPE and no formation of a new product.Fig 8also permitted to observe that CSH possesses high crystallized hydrates, namely the ettringite and the portlandite Moreover, the spectrum shows a high hydra-tion In details, the ettringite reaches its highest peaks at about 18.09°2h, 34.09°2h and 47.12°2h and calcite CaCO3 reaches its highest peak at 29.41°2h Peak of about 23.02°2h corresponds to gypsum formation A rearrangement of the crystalline structure
1.25 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 2
2.05 2.1 2.15 2.2 2.25 2.3
Thermal Conductivity (W/m.K)
OM MA MA/PE2
MA/PE6
7 14 28 90 120 0
0.2 0.4 0.6 0.8 1
Days
(a)-Temperature 20°C
7 14 28 90 120 0
0.2 0.4 0.6 0.8 1
Days
(b)-Temperature 140°C
7 14 28 90 120 0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Days
(c)-Temperature 250°C
7 14 28 90 120 0
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Days
(d)-Temperature 350°C
Fig 6 Variation of thermal diffusivity of mortars with temperature.
Trang 7occurred therefore during cement hydration, as absorption bands
characterizing anhydrous clinker, are replaced by the hydration
particles
Fig 9shows the XDM spectrum of MA/PE6 One can observe
that the spectrum does not indicate significant difference in terms
of crystalline structures concerning the binding materials In
gen-eral, the spectrum shows the presence of identical materials such
as portlandite, ettringite, calcite and gypsum However, the
spec-trum highlights the presence of high and intensive peaks of quartz,
characterizing the presence of silica due to the adjuvant
incorpo-rated Similarly, the portlandite peak of OM (18.09°2h) is slightly
greater than that of MA/PE6 because of the high rate of silica
(90%) relative to portlandite and partly of the incorporation of
HDPE (6%) in the cement causing therefore a progressive decrease
of portlandite in the PMM relative to OM
Even for this PMM, the spectrum does not exhibit any other
phases than those observed for the OM However, portlandite
crys-tals Ca(OH)2may possibly produce a sharper reflection in the plane
of diffraction in the presence of HDPE because of any change in the
arrangement of the crystals This sharper reflection resulted from
the effect acquired by the lower quantity of Ca(OH)2 Therefore,
the peak intensity for a 6% addition of polymer in the HDPE is
admitted as high portion as suggested by Benosman et al.[29]
3.6 Differential Calorimetry Scanning For Differential Calorimetry Scanning (DCS) analysis, tests on PMM and OM samples were conducted under a linear heating starting from room-temperature (20 °C) up to 550 °C and a heating speed of 10 °C/min.Fig 10shows the DSC curve of OM Two high endo-thermal reactivations took place during the heating of the sample, namely (1) the evaporation of a part of the adsorbed water
at about 100–200 °C and at different steps of the dehydration of CSH; (2) the dehydration of calcium hydroxide between 450 °C and 550 °C It is shown inFig 11that the effect of the added quan-tity of HDPE in the polyphase material highly affects the DSC curve implying a fall in the intensity of endo-thermal peak (119.9 °C), a widening of exothermal effect between 200 °C and 400 °C and a loss of weight on the dehydration of portlandite at 472 °C 3.7 Scanning Electron Microscope observations
Scanning Electron Microscope (SEM) tests are performed using HITACHI TM-1000 the apparatus This part of the study focuses upon visualising the cement and HDPE morphologies under differ-ent temperatures, as shown inFig 12 At room-temperature, SEM photographs show that OM has a compact structure and depicts
0 200 400 600 800 1000 1200 1400 1600
E
2 Theta
OM-20°C
P
Q G
Q C
P Q
G CaO
E:Ettringite P:Portlandite C:Calcite Q:Quartz G:Gypsum
Fig 8 XRD spectrum of reference mortar.
0 200 400 600 800 1000 1200 1400
E
P Q Q
P Q
C
E:Ettringite P:Portlandite C:Calcite Q:Quartz G:Gypsum
2 Theta
MA/PE6-20°C
Fig 9 XRD spectrum of MA/PE6.
Trang 8the appearance of hydrated phases such as the portlandite in
crys-tals shapes and frost of CSH in granular heap Similarly, MA/PE6 is
characterized by the appearance of a particle of HDPE surrounded
by cement With the increase of temperature, MA/PE6 becomes
less compact and deteriorates This phenomenon is clearly marked
by the existence of pores of 108lm in size at 250 °C and of 162lm
at 350 °C Cracks were also formed because of the absence of HDPE,
letting the pores becoming the entry points for air Anew, this
con-firms the results obtained for thermal properties quoted in
scien-tific literature
3.8 Compressive strength
In order to acquire knowledge of the effect of HDPE upon the
mechanical properties of MA/PE2, MA/PE4 and MA/PE6 mortars,
4 4 16 cm3 samples were tested OM and MA mortars were
also considered for a direct comparison However, the
experimen-tal results presented are average values All the samples of the
dif-ferent mortars were kept in the same conditions in terms of
temperature and humidity
The evolution of the compressive strengths for the mortars is
shown inFig 13 The measurements were for the period lying
be-tween day 7 and day 120 One can observe that the compressive strength of all the mortars regularly increases with the different ages of the samples One can also observe that the increase of HDPE content caused a significant decrease in the compressive strengths
of the PMM For instance, if one examines MA/PE2 and MA/PE6 at day 7, the corresponding compressive strengths are 12.58 MPa and 8.46 MPa So, a decrease of 32.74% is observed Similarly, the com-pressive strengths of MA/PE4 and MA/PE6 at day 14 are 16.79 MPa and 12.24 MPa, respectively, which gives a decrease of 27.10% This means that although the compressive strength of cement normally increases during the first month because of hydration and filling of pores by hydrates, the presence of HDPE within mortars slowed down the speed of kinetic hydration during all the curing period (120 days) In addition, the compressive strength of MA/PE6 is re-duced of about 12.52%, after day 28 when compared to OM The progression of the various compressive strengths is similar for all mortars and a rapid increase for the period lying between day 7 and day 28 However after day 28, the evolution of the com-pressive strength becomes very slower In details, after day 28 and
up to day 120, the evolution of the PMM (MA/PE2, MA/PE4 and MA/PE6) compressive strengths are increased by 15.89%, 20.60% and 18.68%, respectively
-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1
Temperature (°C)
MA/PE6
Fig 11 DSC study of MA/PE6.
-120 -100 -80 -60 -40 -20 0 20
Temperature (°C)
OM
Fig 10 DSC study of OM.
Trang 9Unlikely, MA performed better results and the compressive
strength progressed regularly and an increase of 50.08% was
ob-served when compared to OM at day 28 For this mortar, the 3%
of adjuvant was substituted to cement permitted the infusion of Fig 12 SEM photographs of OM and MA/PE6 at different temperatures.
Trang 10nano-silicates Nano-silicates therefore highly enhanced the
pouzzolanic activity and consequently increased the compressive
strength despite the low W/C ratio of 0.45 for MA in comparison
to that of OM (W/C = 0.6)
3.9 Tensile strength
Measured tensile strengths of all mortars are shown inFig 14
One can observe that the tensile strengths of the different PMM
are higher to that of OM, including MA/PE6 Insofar as the tensile
strength for PMM is concerned, one can notice that no correlation
can be established between the tensile strength and the content of
HDPE within the samples.Fig 14also reveals that MA has the
high-est tensile strength
4 Conclusion
In this study dealing with experimental study on
thermo-mechanical properties of Polymer Modified Mortar, one may list
the following findings:
Thermal property characterized by thermal conductivity, by cal-orific capacity and by diffusivity is improved when HDPE is added by substitution of cement The increase of polymer grade reduces the thermal properties of mortars Thermal conductiv-ity is straightforwardly related to the densconductiv-ity of mortars; the lower the conductivity: the lower the density of mortars, the lower the conductivity
XDM study shows that there is no generation of new material
by introducing HDPE There is only a physical reaction between cement and polymer
Differential Scanning Calorimetry (DSC) has the same appear-ance for both reference and composite mortars This latter is characterized by a decrease of the endothermal peak and by a loss of weight on portlandite dehydration which shows off the HDPE substitution
SEM observations permitted to investigate the state of the cement matrix after increase of temperature which caused for-mation of pores and therefore the decrease of the thermal characteristics
Mechanical properties decrease with the increase of polymer grades but they remain above that of reference OM A certain level of HDPE substitution has therefore to be respected
2 3 4 5 6 7 8 9 10 11 12
Days
OM MA MA/PE2 MA/PE4
Fig 14 Tensile strength increase during time.
5 10 15 20 25 30 35 40 45
Days
OM MA MA/PE2 MA/PE4
Fig 13 Compressive strength increase during time.