NCB being a premier R&D organization for cement and construction sector in Inida has executed a number of R&D and consultancy projects related to waste utilization and energy conservation. Outcomes of these project is helping to Indian cement industry for contributing towards the circular economy and sustainable manufacturing. Some of them are highlighted below.
Production of Synthetic Slag from Low Grade Limestone
A Study were carried out at NCB laboratory for development of Synthetic Slag using low-grade limestone. Laboratory slag samples prepared with low-grade limestones and other additive materials, which found to be conforming the IS: 12089-1987. These laboratories made synthetic slag samples as shown in Fig. 18.2 were also investigated by optical microscopy as shown in Fig. 18.3 and found to have maximum 92% glass content, which is greater than 85% as specified in IS-12089. PSC samples were prepared with 40 and 60% synthetic slag replacing equal quantity of clinker. The performance of PSC blends prepared using synthetic slag sample were found as per requirements of Indian Standard Specification, IS: 455-1989 for PSC. As the limestone, which is getting depleted and has reached to an alarming level where the availability of cement grade limestone in India has reduced to 8949 million tones only, Synthetic Slag may play a vital role to replace clinker or indirectly cement grade limestone. However, main challenge would be to produce this slag at industrial scale.
Alternative Fuels Utilization
NCB has vast experience of analytical studies, trial runs and system design for Alternative Fuels (AFs) utilization. NCB has carried out various studies, which covers the impact assessment of AFs on overall process. Recently, number of studies have been carried out for cement plants. One study for utilization of Tyre Derived Fuel (TDF) as alternative fuel for co-processing. TDF ash sample was tested at NCB laboratory, and Zinc content was found to be around 4.06%, which is equivalent to 0.03% by weight in clinker. Several investigations have already revealed that zinc concentration above 500 ppm in clinker impact the workability of cement. Considering the impact of addition of Zinc in clinker, plant can achieve around 21% Thermal Substitution Rate (TSR) however, TSR beyond 21% may not be feasible due to higher zinc content in TDF. Another study was done for a cement plant (located in North Karnataka, India) to handle more than 25 types of alternative fuels, plant was commissioned a year back and now utilizing waste as a fuel with more than 10% TSR. NCB is also doing projects for system design to handle five different types of alternative fuels for a cement plant located in South & Central part of India.
Dolomitic Limestone Utilization
NCB in one of its recent projects has successfully utilized of up to 15% dolomite as an additive replacing equal quantity of clinker. The cement performance was found to be similar to that of control cement prepared without dolomite.
Performance Improvers in Cement Manufacturing
Based on studies on number of industrial wastes by NCB, the Bureau of Indian Standards (BIS) has permitted the use of copper slag, LD slag, lead-zinc slag and catalytic waste from petroleum refinery as performance improvers in manufacture of OPC.
Bottom Ash Utilization
In a recent R & D work, NCB has developed tiles and bricks by utilization of ~30% bottom ash along with fly ash. Cementitious binders with consistent strength property were prepared using rationalized formulations and curing conditions. The pre-cast bodies like tiles (150 × 75 × 25 mm) were meeting test limits of IS 2690 (Part 2):1992 and bricks having dimensions of 190 × 90 × 40 mm were meeting the requirement of strength and water absorption of Class 15 of IS 1077 (Part 2):1992. In another research activity at NCB, Bottom Ash is also successfully utilized as 50% replacement of fine aggregate in concrete.
Composite Cement Production
NCB has carried out several studies on composite cement wherein combinations of fly ash and granulated blast furnace slag were used for preparing composite cement blends. BIS has brought out standard specification IS: 16415-2015 for composite cement on recommendations of NCB.
Alternative Raw Materials Utilization
NCB has done an investigative study to utilize 15 inorganic industrial wastes including limes sludge, Wolstanite, leather sludge, Jarosite, LD slag, red mud and marble slurry in cement manufacture and as aggregate in concrete.