Cement, Energy & Environment

, small-sized uniform clusters of C-S-H and lead to denser microstructure c) Nano-particles improve the structure of the aggregates' contact zone, resulting in a better bond between aggregates and cement paste d) Nano-particles fill the voids between the cement grains, resulting in the immobilization of "free water'' (filler effect) e) Well dispersed nano-particles improve the segregation resistance and workability of the system with toughness, shear, tensile and flexural strength of cement based materials Use of nano-particles for reinforcement of cementitious matrix and Cement based nano– composite materials The cementitious materials, though quite strong in compression, are relatively weak in Figure 2 Carbon nanotubes flexure and have low bending strengths and fracture toughness . Fibre reinforcement of cementitious matrices improves their flexural strength as well as toughness by impeding crack formation and growth. Reinforcement of cementitious binders with high strength nanodiameter fibres is now being investigated to achieve high performance cement based composites. Carbon nanotubes (CNTs) are cylindrical in shape with diameter of just a few nanometers but they can be several millimeters in length (Figure 2) . Further Research Requirements The R&D efforts for nanoscale investigations of cements and concrete and developing nanotechnology based new products needs to be further accelerated to achieve the various expected benefits outli ned above. In particular the investigations on the role of nanoparticles of different sizes and different materials in modifying the properties of cementitious binders and concrete and on the safe handling of nanoparticles may provide useful results in the form of improved cements and special concretes with enhanced durability. The present high cost of nanoparticles needs to be brought down for favorable economics of their utilization, and R&D efforts are therefore also required for developing economical processes for production of nanoparticles including carbon nanotubes. Presently there is not much reported work on nano catalysts for low temperature clinkerization but the available information indicates that further work in this direction may be fruitful. Biomass Co-Firing Process and Technology, Efficiency, Potential and Impact Biomass co-firing reduces greenhouse gas (GHG) emissions from coal-fired power and enables high efficiency power generation from biomass in modern, large-size coal fired plants-much higher than the efficiency of hundred per cent dedicated biomass power plants. Biomass co-firing consists of combusting biomass and fossil fuels , mostly coal but also natural gas, in the same power plant. In most cases , biomass co-firing in coal power plants takes place by mixing biomass with coal before burning, but biomass can also be gasified and burned in separate burners , after which the gaseous fuel or steam is mixed with the boiler streams of the coal– fired power plant. The advantage of biomass co firing is that it reduces greenhouse gas (GHG) emissions from coal-fired power and enables power generation from biomass with the high efficiency achieved in modern, large size coal-fired power plants, which is much higher than the efficiency of dedicated, 100 per cent biomass 7