Utilizing Fly Ash Cenosphere and Aerogel for Lightweight Thermal Insulating Cement-Based Composites
Thermal insulating composites help to reduce the total power consumption in a building by creating a barrier between external and internal environment. Such composites can be used in the roofing tiles or wall panels for exterior surfaces. This study purposes to develop lightweight cement-based composites for thermal insulating applications. Waste materials like silica fume (an industrial by-product) and fly ash cenosphere (FAC) (hollow micro-spherical shells obtained as a waste residue from coal fired power plants) were used as partial replacement of cement and lightweight filler, respectively. Moreover, aerogel, a nano-porous material made of silica, was also used in different dosages for improved thermal insulating behavior, while poly vinyl alcohol (PVA) fibers were added for enhanced toughness. The raw materials including binders and fillers were characterized by X-Ray Diffraction (XRD), X-Ray Fluorescence spectroscopy (XRF), and Brunauer–Emmett–Teller (BET) analysis techniques in which various physical and chemical properties of the raw materials were evaluated like specific surface area, chemical composition (oxide form), and pore size distribution (if any). Ultra-lightweight cementitious composites were developed by varying the amounts of FAC and aerogel with 28-day unit weight ranging from 1551.28 kg/m3 to 1027.85 kg/m3. Excellent mechanical and thermal insulating properties of the resulting composites were obtained ranging from 53.62 MPa to 8.66 MPa compressive strength, 9.77 MPa to 3.98 MPa flexural strength, and 0.3025 W/m-K to 0.2009 W/m-K as thermal conductivity coefficient (QTM-500). The composites were also tested for peak temperature difference between outer and inner surfaces when subjected to heating (in a specially designed experimental set-up) by a 275W infrared lamp. The temperature difference up to 16.78 oC was achieved, which indicated outstanding properties of the developed composites to act as a thermal barrier for building envelopes. Microstructural studies were carried out by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) for characterizing the inner structure of the composite specimen. Also, the hydration products were quantified using the surface area mapping and line scale technique in EDS. The microstructural analyses indicated excellent bonding of FAC and aerogel in the cementitious system. Also, selective reactivity of FAC was ascertained from the SEM imagery where the partially consumed FAC shells were observed. All in all, the lightweight fillers, FAC, and aerogel helped to produce the lightweight composites due to their physical characteristics, while exceptional mechanical properties, owing to FAC partial reactivity, were achieved.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1339802Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1577
 M. Khan, Factors affecting the thermal properties of concrete and applicability of its prediction models, Build. Environ. 37 (2002) 607–614. doi:10.1016/S0360-1323(01)00061-0.
 K.-H. Kim, S.-E. Jeon, J.-K. Kim, S. Yang, An experimental study on thermal conductivity of concrete, Cem. Concr. Res. 33 (2003) 363–371. doi:10.1016/S0008-8846(02)00965-1.
 R. Demirboǧa, R. Gül, Thermal conductivity and compressive strength of expanded perlite aggregate concrete with mineral admixtures, Energy Build. 35 (2003) 1155–1159. doi:10.1016/j.enbuild.2003.09.002.
 R. Demirboǧa, R. Gül, The effects of expanded perlite aggregate, silica fume and fly ash on the thermal conductivity of lightweight concrete, Cem. Concr. Res. 33 (2003) 723–727. doi:10.1016/S0008-8846(02)01032-3.
 L.H. Nguyen, a. L. Beaucour, S. Ortola, a. Noumowé, Influence of the volume fraction and the nature of fine lightweight aggregates on the thermal and mechanical properties of structural concrete, Constr. Build. Mater. 51 (2014) 121–132. doi:10.1016/j.conbuildmat.2013.11.019.
 H.K. Kim, J.H. Jeon, H.K. Lee, Workability, and mechanical, acoustic and thermal properties of lightweight aggregate concrete with a high volume of entrained air, Constr. Build. Mater. 29 (2012) 193–200. doi:10.1016/j.conbuildmat.2011.08.067.
 H. Uysal, R. Demirboǧa, R. Sahin, R. Gül, The effects of different cement dosages, slumps and pumice aggregate ratios on the thermal conductivity and density of concrete, Comput. Concr. 3 (2006) 163–175. doi:10.1016/j.cemconres.2003.09.018.
 T.Y. Lo, W.C. Tang, H.Z. Cui, The effects of aggregate properties on lightweight concrete, Build. Environ. 42 (2007) 3025–3029. doi:10.1016/j.buildenv.2005.06.031.
 V. Ducman, A. Mladenovic, Lightweight aggregate based on waste glass and its alkali – silica reactivity, 32 (2002) 223–226.
 J.Y. Wang, K.S. Chia, J.Y.R. Liew, M.H. Zhang, Flexural performance of fiber-reinforced ultra lightweight cement composites with low fiber content, Cem. Concr. Compos. 43 (2013) 39–47. doi:10.1016/j.cemconcomp.2013.06.006.
 M.R. Wang, D.C. Jia, P.G. He, Y. Zhou, Microstructural and mechanical characterization of fly ash cenosphere/metakaolin-based geopolymeric composites, Ceram. Int. 37 (2011) 1661–1666. doi:10.1016/j.ceramint.2011.02.010.
 X. Liu, K.S. Chia, M.-H. Zhang, Development of lightweight concrete with high resistance to water and chloride-ion penetration, Cem. Concr. Compos. 32 (2010) 757–766. doi:10.1016/j.cemconcomp.2010.08.005.
 L.N. Ngu, H. Wu, D.K. Zhang, Characterization of ash cenospheres in fly ash from Australian power stations, Energy and Fuels. 21 (2007) 3437–3445. doi:10.1021/ef700340k.
 X. Huang, R. Ranade, Q. Zhang, W. Ni, V.C. Li, Mechanical and thermal properties of green lightweight engineered cementitious composites, Constr. Build. Mater. 48 (2013) 954–960. doi:10.1016/j.conbuildmat.2013.07.104.
 J.Y. Wang, M.H. Zhang, W. Li, K.S. Chia, J.Y.R. Liew, Stability of cenospheres in lightweight cement composites in terms of alkali-silica reaction, Cem. Concr. Res. 42 (2012) 721–727. doi:10.1016/j.cemconres.2012.02.010.
 J.Y. Wang, Y. Yang, J.Y.R. Liew, M.H. Zhang, Method to determine mixture proportions of workable ultra lightweight cement composites to achieve target unit weights, Cem. Concr. Compos. 53 (2014) 178–186. doi:10.1016/j.cemconcomp.2014.07.006.
 A. Hanif, S. Diao, Z. Lu, T. Fan, Z. Li, Green lightweight cementitious composite incorporating aerogels and fly ash cenospheres – Mechanical and thermal insulating properties, Constr. Build. Mater. 116 (2016) 422–430. doi:10.1016/j.conbuildmat.2016.04.134.
 T. Gao, B.P. Jelle, A. Gustavsen, S. Jacobsen, Aerogel-incorporated concrete: An experimental study, Constr. Build. Mater. 52 (2014) 130–136. doi:10.1016/j.conbuildmat.2013.10.100.
 E. V. Fomenko, N.N. Anshits, M. V. Pankova, L.A. Solovyov, A.G. Anshits, Fly Ash Cenospheres: Composition, Morphology, Structure, and Helium Permeability, World Coal Ash Conf. - May 9-12, 2011, Denver, CO, USA. (2011) 2011.
 Y. Wu, J.Y. Wang, P.J.M. Monteiro, M.H. Zhang, Development of ultra-lightweight cement composites with low thermal conductivity and high specific strength for energy efficient buildings, Constr. Build. Mater. 87 (2015) 100–112. doi:10.1016/j.conbuildmat.2015.04.004.
 R. Demirboǧa, Thermal conductivity and compressive strength of concrete incorporation with mineral admixtures, Build. Environ. 42 (2007) 2467–2471. doi:10.1016/j.buildenv.2006.06.010.
 R. Demirboǧa, Influence of mineral admixtures on thermal conductivity and compressive strength of mortar, Energy Build. 35 (2003) 189–192. doi:10.1016/S0378-7788(02)00052-X.
 A.C. Pierre, G.M. Pajonk, Chemistry of aerogels and their applications, Chem. Rev. 102 (2002) 4243–65.
 T. Woignier, J. Phalippou, Mechanical strength of silica aerogels, J. Non. Cryst. Solids. 100 (1988) 404–408. doi:10.1016/0022-3093(88)90054-3.
 ASTM D790-10, Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials, Am. Soc. Test. Mater. (2010). doi:10.1520/D0790-10.
 ASTM C109, Standard Test Method for Compressive Strength of Hydraulic Cement Mortars, Am. Soc. Test. Mater. (2002).
 ACI Committee 318, Building Code Requirements for Structural Concrete (ACI 318M-08), 2007.
 S.W. Tang, E. Chen, H.Y. Shao, Z.J. Li, A fractal approach to determine thermal conductivity in cement pastes, Constr. Build. Mater. 74 (2015) 73–82. doi:10.1016/j.conbuildmat.2014.10.016.