Study High Performance Thermal Properties of Natural Pumice-Based Bricks

Abstract

Aims: Characterization of the thermal properties of natural pumice-based lightened bricks under ASTM standards, analyzing thermal conductivity to promote thermal comfort inside buildings. Study Design: The project had four stages. The first was getting the base material (pumice). The second was developing of lightened test specimens. The third was focused on the characterization and fourth intended for the interpretation and analysis of the test results and conclusions of the project. Place and Duration of Study: Universidad Autónoma de Querétaro, from January to December, 2012. Methodology: XRD by powders with a diffractometer Bruker D-8 Advance, Cu anode at 30 KV and 30 mA, Cu Ka radiation λ = 1.54 A, from 10 to 90º on the 2θ scale at 2º /min. Mechanical tests according to ASTM C109/C109M-08, minimum compressive strength at 28 days of 7.8 N/mm2. X-Ray Fluorescence with Spectrometer SIEMENS fluorescence X-ray SRS 3000. Thermal conductivity using ASTM C177: Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded Hot-Plate Apparatus. Results: Pumice was identified as pozzolanic material with crystalline phases of significant silica-aluminate content by X-Ray diffraction. X-Ray Fluorescence analysis confirmed the elements of the pumice, therefore this analysis confirmed the presence of Si dominant, followed by Al. Lightened bricks were developed meeting the specifications of resistance of the ASTM standards, and the properties of thermal conductivity are better than traditional sand-cement bricks; density and porosity could create a zone of thermal comfort within buildings. Apparent thermal conductivity of pumice specimens was 0.336W m-1K-1, thermal resistance 0.234W-1m2K and Expanded Uncertainty (k=2) 5%. Conclusion: Due to porosity together with worthy mechanical comportment, the natural pumice-based bricks have advantages in lighter weight-effort, tensile strength and higher thermal insulation characteristics. The analyzed pumice reduces the thermal conductivity coefficient of lightened bricks. Thermal conductivity of lightweight bricks elaborated in this work implies a superior insulation material, comparable to the highest quality insulation materials.