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Around three billion tons of cement are produced around the world each year (Guillaume, 2014), of which the majority is consumed in developing countries due to ceaselessly growing demand, attributed to their emerging economies.
In addition to the construction activities, natural disasters such as earthquakes and wars lead to the destruction of many infrastructures, increasing the constant demand for cement and cement-based materials such as mortar and concrete.
Mortar is cement mixed with fine sand, water and lime to improve the durability of the product. It is generally used as a paste that holds together other common materials of masonry construction, including bricks, concrete blocks and stone.
Although mortar has many advantages, it is less resistant to earthquakes, brittle, and has low tensile strength. These drawbacks have led scientists to investigate multiple alternative solutions, including the use of nanoparticles.
Nanoparticles to Enhance the Properties of Cement Mortar
Since the famous lecture of Richard Feynman on “There’s Plenty of Room at the Bottom” to the American Physical Society meeting in 1959, nanotechnology has evolved as the “bottom-up” approach for controlling matter at 1 and 100 nanometers.
With their distinctive favorable properties of large surface area, high functional density, extraordinary surface effect, and high strain resistance (Mohajerani, et al., 2019), nanoparticles have taken a vital role in various applications. They are thought to enhance the material properties and transform unique phenomena into innovative applications.
Over the last decade, many researchers have explored the use of nanoparticles in the construction industry to produce cement-based materials with superior properties.
Adding metal oxide nanoparticles to cement reduces its permeability to ions, increasing its strength and durability (Al-Rifaie & Ahmed, 2016).
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Some of the investigated nanoparticles are nano-SiO2, TiO2, Al2O3, Fe2O3 carbon nanotubes, carbon nanofibers, graphene, and graphite oxide (Ramakrishna & Sundararajan, 2019). However, nano-SiO2 is considered to be the most frequently used nanoparticle due to its nanosize and pozzolanic reaction (Wang, Zhang , & Gao, 2018).
The mechanical strength of cement mortar is mainly associated with the homogeneous distribution and density of the hydrated product, such as calcium silicate hydrate (C-S-H) gels, from the hydration of the tricalcium silicate (C3S) and dicalcium silicate (C2S).
Nanoparticles improve the strength and the durability of concrete by stimulating the hydration reaction and filling the micropores in the cement paste structure. This decreases the porosity of concrete, which improves the strength and mechanical properties of cement mortar (Ramakrishna & Sundararajan, 2019).
Characteristics of Cement Mortar with Nanoparticles
Cavazos et.al (Cavazos, et al., 2017) investigated the mechanical properties of cement mortar with the use of multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs).
In comparison with the plain cement mortar, the addition of 0.1% concentration of MWCNTs increased the compression strength by 56%, whereas concentrations of 0.1% of HNTs increased by 31%.
The agglomeration of the nanoparticles was also observed in MWCNTs, which led to the concept of using lower concentration. A 15% improvement in compression strength and 36% in tensile strength at concentrations of 0.5% were achieved when using MWCNTs nanoparticles (Kumar, Kolay, Malla, & Mishra, 2015).
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The use of HNTs was also approved by another group (Farzadnia, Ali, Demirboga, & Anwar, 2013) to enhance the compressive strength by 24% at concentrations of 3%.
The physical and mechanical properties of the effect of TiO2 nanoparticles on cement mortar under different temperatures of 0°C, 5°C, and 10°C were analyzed and compared with the ambient temperature of 20 °C (Wang, Zhang , & Gao, 2018). The result indicated that 2 wt.% TiO2 nanoparticles is the optimum concentration that could accelerate the hydration of cement mortar in general, although low temperatures had an undesirable impact on the setting time of cement mortar.
The hydration rate decreases at low temperaturse, which ultimately slows down the production of hydration products (Wang, Zhang , & Gao, 2018). This generates the unfilled pores in the matrix, requiring additional time to produce a dense microstructure. The presence of nanoparticles with a large surface area to volume ratio allows an appropriate environment for the production of more hydration products (Wang, Zhang , & Gao, 2018).
Reducing Environmental Impacts using Nanoparticles in Cement
The use of nanoparticles is an effective solution to reduce the environmental impact associated with concrete production.
Sadeghi-Nik et.el (Sadeghi-Nik, Berenjian, Bahari, Safaei, & Dehestani, 2017) experimented with the combined possible solution to enhance the mechanical strength and reduce the environmental impact by replacing 1, 2 and 3 wt% of cement with nano-montmorillonite and nano-Titanium (nano-MT) particles in cement mortar.
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The result demonstrated that cement with nano-MT particles up to 1 wt% as an optimum percentage enhances the microstructure and mechanical properties, and reduces greenhouse gas emissions.
From the research above, it has been significantly suggested that the implementation of nanoparticles enhances the overall characteristics of cement mortar and improves its strength for constructional applications.
References and Further Reading
Al-Rifaie, W. N., & Ahmed, W. K. (2016) Effect of Nanomaterials in Cement Mortar Characteristics. Journal of Engineering Science and Technology, 11(9), 1321-1332.
Cavazos, J. S., González, G., Kharissova, O. V., Ortega, B., Peña, L., Osorio, M., & Garza-Castañón, M. (2017) Effect of Nanoparticles on Mechanical Properties of Cement-Sand Mortar Applications. Advances in Chemical Engineering and Science, 7(3). doi:10.4236/aces.2017.73020
Farzadnia, N., Ali, A. A., Demirboga, R., & Anwar, M. P. (2013) Effect of halloysite nanoclay on mechanical properties, thermal behavior and microstructure of cement mortars. Cement and Concrete Research, 48, 97-104. doi:10.1016/j.cemconres.2013.03.005
Guillaume, H. (2014) Assessing the environmental impact of conventional and ‘green’ cement production. In Eco-efficient Construction and Building Materials (pp. 199-238). Woodhead Publishing. doi:10.1533/9780857097729.2.199
Kumar, S., Kolay, P., Malla, S., & Mishra, S. (2015) Effect of Multiwalled Carbon Nanotube in Cement Composite on Mechanical Strength and Freeze-Thaw Susceptibility. Advances in Civil Engineering Materials, 4(1), 257-274. doi:10.1520/ACEM20150006
Mohajerani, A., Burnett , L., Smith, J. V., Kurmus, H., Milas , J., Arulrajah , A., . . . Kadir , A. A. (2019) Nanoparticles in Construction Materials and Other Applications, and Implications of Nanoparticle Use. Materials, 12(19). doi:10.3390/ma12193052
Ramakrishna, G., & Sundararajan, T. (2019) A novel approach to rheological and impact strength of fibre-reinforced cement/cementitious composites for durability evaluation. Durability and Life Prediction in Biocomposites, Fibre-Reinforced Composites and Hybrid Composites, 389-406. doi:10.1016/B978-0-08-102290-0.00017-9
Sadeghi-Nik, A., Berenjian, J., Bahari, A., Safaei, A. S., & Dehestani, M. (2017) Modification of microstructure and mechanical properties of cement bynanoparticles through a sustainable development approach. Construction and Building Materials, 155, 880-891. doi:10.1016/j.conbuildmat.2017.08.107
Wang, L., Zhang , H., & Gao, Y. (2018) Effect of TiO2 Nanoparticles on Physical and Mechanical Properties of Cement at Low Temperatures. Advances in Materials Science and Engineering. doi:10.1155/2018/8934689