Objectives: Bricks being the most frequently used product in the local construction industry. However, there has been very little or no relevant information about the manufacturing standards and quality of locally-made bricks as compared to that in developed countries. It is the aim of this study to provide some information about the local raw brick-materials as well as of the bricks manufactured from these. Materials and Methods: Samples of soil and bricks were collected from two representative kilns of district Peshawar (Pakistan). Fine powders of both of these were obtained by manual triturating in a pestle and mortar system. XRD was performed for phase analysis using powder X Ray Diffractometry (JEOL, JDX 3500) system. SEM studies for micro-structural analysis of brick samples (4x4x4 mm3) were also carried out using a JSM-5910 JEOL SEM. For SEM, samples were fine polished with a twin prep 3TM grinding polishing machine. The smooth polished surfaces were chemically etched with 5% HF solution for one minute. Finally, the samples were mounted onto stubs with silver paint and gold coated in order to avoid charging in the SEM.

Results: X-ray diffraction revealed that raw brick soils in use by the local brick-industry comprised predominantly of quartz, albite and chlorite along-with illite, melilite, calcite and orthoclase. In the processed brick-samples, mullite and cristobalite were not observed in SEM indicating the use of a lowfiring temperature (~ 1000oC) and absence of kaolinite in raw materials. Consequently, the local brick specimens were expected to be more porous and mechanically weak as compared to those from advanced countries. The direct naked eye examination of the sample brick had non-uniform colour and the presence of pebbles a further indication of non-professional processing of initial raw ingredients. Cracks seen in the fired brick samples were seen as further indication of improper heat-treatment and processing. SEM EDS of brick-samples showing the presence of iron was seen as the cause of red colour in the brick.

Conclusions: The use of low-temperature firing cycle, rapid cooling, and absence of kaolinite in raw materials were seen as the main factors leading to bricks with compromised quality.