Physical and mechanical properties of seven ancient clay brick samples of Kathmandu valley consisting of quartz, feldspars, spinel, margarite, muscovite type of mica mineral and hematite were studied using ASTM standards. All the brick samples used in this study have the water absorption, apparent porosity and bulk density in the range of 10-28 percent, 17-33 percent and 1.2-1.8 g/cm3, respectively, while the compressive strength of all the brick samples is found to be in the range of 5-23 MPa. The bulk density of the tile samples is found to be increased with decreasing the water absorption and apparent porosity. The compressive strength of all the clay brick samples can be correlated with their physical properties. Consequently, durability of the ancient bricks is directly influenced by their physical properties of water absorption, apparent porosity and bulk density.

The total eight clay brick samples including five archaeologically importance samples from different historical sites and three samples from more than a century old buildings of Kathmandu valley were collected and their mineralogical phases were characterized using X-ray diffraction and Fourier transform infrared spectroscopic methods in this study. Mineralogical phases existed in these archaeological and ancient clay bricks are identified as quartz, feldspars, spinel, muscovite, margarite and hematite in accordance with the powder diffraction standard files. The degree of the disappearance of feldspars phase and appearance of the spinel phase in all the brick samples is found to be different indicating that the firing temperature applied to produce these brick specimens should not be same. The firing temperature applied for the production of the eight clay brick samples should be in the range of 900°-1000° C. Most of the archaeological clay brick samples used in this study should be produced by firing at the high-temperature comparison with those brick samples used in old buildings of Kathmandu valley.

Present research work was focused to investigate the firing temperature effects on mineralogical phase composition of nine clay bricks collected from the brick factory of Kathmandu valley using X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra analyses. Main mineralogical phases of quartz, feldspars, spinel, mullite and hematite in the brick specimens fired at different firing temperatures including muscovite type of mica mineral in the sun-dried brick specimen are identified from XRD and FTIR analyses. Disappearance of the muscovite type of mica clay mineral with feldspars enhanced to form alumina rich spinel phase at firing 900° to 1000° C, and finally the primary mullite phase in the fired clay brick samples is clearly observed at 1100° C firing temperature.BIBECHANA 16 (2019) 122-130

Uses of clay brick have practiced since ancient times in the Kathmandu valley of Nepal as structural materials for the construction of historical monuments, temples, and even modern buildings so on. However, their durability and sustainability properties are less studied scientifically in Nepal. Taking into consideration, analysis of mineralogical phases and physico-mechanical properties of modern clay bricks of Nepal was carried out using X-ray powder diffraction as well as Fourier transform infra-red techniques, and American Standards for Testing Materials standards, respectively. Quartz, feldspars, alumina-rich spinel, muscovite, primary mullite, and hematite are constituent in the bricks. Appearance of the spinel and primary mullite phases in burnt brick samples with diminishing feldspar peaks were to be different, indicating that the temperature applied for the making of these clay bricks presumed to be between 900 and 1050 °C. All the commercially used contemporary brick samples analyzed herein could be of II and III classes based on the estimated physical and mechanical properties. They showed the water absorption capacity (W AC ), apparent porosity (P A ), bulk density (D B ), and compressive strength (S C ) in the range of 5-30%, 10-40%, 1.1-2.15 g/cm 3 , and 3.35-10.53 MPa, respectively, and these properties have a reasonable correlation. The S C is to be decreased exponentially with increasing both the W AC and P A and increased exponentially with D B .