Feasibility study of carbon black contaminated silica sand in the production of black blocks

Abstract

Present study attempted to verify the feasibility of producing cement blocks by partially replacing fine aggregates with carbon black contaminated silica sand (CBCSS), which is a by-product of the tyre manufacturing process. In the present study performance tests such as compressive testing and flexural testing were conducted. In addition resistance against rain drops was measured and the quality of water, in case of inundation was also checked. As experimental investigations, eight individual black blocks were cast and tested for compressive strength and nine sample panels were made and tested for flexural and compressive strengths. In addition, pressurized drizzle test was conducted for individual blocks to study the erosion resistance characteristics against rain. Moreover, particularly in lower lands, during floods there is a room for these panels containing CBCSS being immersed under water for certain days. The present study accommodated the above through water quality test and the results were verified with drinking water specifications. Compressive strength of individual black blocks was 4.74 N/mm2, which is well above to that of the minimum requirement of 1.2 N/mm2 as per the SLS 855: Part 1: 1989. These blocks, according to the Sri Lankan Standard, could be used for both load bearing walls for up to two storeys and in any non-load bearing walls. The flexural strength parallel to the bed joint was 0.113 N/mm2, which is just below the recommended characteristic flexural strength of 0.2 N/mm2 as per the BS 5628. The flexural strength perpendicular to the bed joint was 0.61 N/mm2, which is higher than the recommended characteristic flexural strength of 0.4 N/mm2 as per the BS 5628. The pressure drizzle test being done to the black blocks was shown smaller indentation after one hour to that of a normal brick at 50 kPa pressure, which revealed a fact that black blocks are rather resistive in terms of indentation to rain to that of normal bricks. Water, in which the black blocks were immersed for three days, satisfied the standard levels for drinkable water, recommended by the SLS 614-1983, which implies the fact that black blocks would not release any additional pollutants to the existing water/flood. Hence, it shall be concluded that the black blocks could be used in constructing masonry walls.