Experimental study on thermo-mechanical properties of polymer modified mortar
Materials and Design 52 (2013) 459–469
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Experimental study on thermo-mechanical properties of Polymer Modiﬁed Mortar Amel Aattache a,⇑, Abdelkader Mahi a, Rabah Soltani a, Mohamed Mouli b, Ahmed Souﬁane Benosman c a
Civil Engineering Department, Faculty of Architecture and Civil Engineering, USTO (Mohamed Boudiaf), BP. 1505, El Menaouar, 31000 Oran, Algeria 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 b
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 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. 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 material in the world and since the early 18th century, and the second after water . Cement is largely used in the preparation of concrete and the demand of this material is in continuous growth to meet the needs of society in terms of housing and buildings construction. 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 problem, plastic wastes such as High Density Poly-Ethylene (HDPE) can be used as partial substitutes to OPC and considered as sustainable building material. Incorporating polymers in mortar and concrete has contributed to propose new structural materials such as Polymer Modiﬁed Mortars (PMMs) and Polymer Modiﬁed Concrete (PMC) . 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 applications, contribute to this excessive demand. In the past, researchers used industrial or plastic wastes such as glass  or ﬁber  in the preparation of self-consolidating ⇑ Corresponding author. Tel.: +213 773886687; fax: +213 41423130. E-mail address: firstname.lastname@example.org (A. Aattache).
0261-3069/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.05.055
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  were largely undertaken. In line with this research, Albano et al.  and Benosman  studied the use of PET in composite polymers. In those studies, Albano investigated the mechanical behaviour of recycled concrete using PET and varying W/C ratio (W/C = 0.5 and 0.6). On his side, Benosman added several percentage of PET by partial substitution to Portland cement. H dration of CSH; (2) the dehydration of calcium hydroxide between 450 °C and 550 °C. It is shown in Fig. 11 that the effect of the added quantity 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 different temperatures, as shown in Fig. 12. At room-temperature, SEM photographs show that OM has a compact structure and depicts
A. Aattache et al. / Materials and Design 52 (2013) 459–469 OM
Temperature (°C) Fig. 10. DSC study of OM.
0.1 0 -0.1
-0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -0.9
Temperature (°C) Fig. 11. DSC study of MA/PE6.
the appearance of hydrated phases such as the portlandite in crystals 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 108 lm in size at 250 °C and of 162 lm at 350 °C. Cracks were also formed because of the absence of HDPE, letting the pores becoming the entry points for air. Anew, this conﬁrms the results obtained for thermal properties quoted in scientiﬁc 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 Â 4 Â 16 cm3 samples were tested. OM and MA mortars were also considered for a direct comparison. However, the experimental results presented are average values. All the samples of the different mortars were kept in the same conditions in terms of temperature and humidity. The evolution of the compressive strengths for the mortars is shown in Fig. 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 compressive 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 reduced 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 compressive 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.
A. Aattache et al. / Materials and Design 52 (2013) 459–469
Fig. 12. SEM photographs of OM and MA/PE6 at different temperatures.
Unlikely, 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
A. Aattache et al. / Materials and Design 52 (2013) 459–469
Compressive Resistance (MPa)
40 35 30 25 20 15
OM MA MA/PE2 MA/PE4 MA/PE6
10 5 0
Days Fig. 13. Compressive strength increase during time.
Tensile Resistance (MPa)
10 9 8 7 6 5 OM
MA MA/PE2 MA/PE4
Days Fig. 14. Tensile strength increase during time.
nano-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 in Fig. 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. 14 also reveals that MA has the highest tensile strength.
4. Conclusion In this study dealing with experimental study on thermomechanical properties of Polymer Modiﬁed Mortar, one may list the following ﬁndings:
Thermal property characterized by thermal conductivity, by caloriﬁc 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 conductivity is straightforwardly related to the density 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 appearance 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 formation 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.
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