http://nopr.niscair.res.in/handle/123456789/12462 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/12472 Title: Compatibility of coarse aggregates with different cements for key characteristics of self-compacting concrete <br/> <br/>Authors: Şahin, Remzi; Akarsu, Meşkure <br/> <br/>Abstract: This paper presents the key characteristics of fresh self-compacting concrete (SCC) made of five types of cements and coarse aggregates with different physical properties. The characteristics of SCC are evaluated in terms of viscosity, flowability, passing ability and segregation resistance of fresh concrete as per the European Guidelines for SCC. It is concluded that all key characteristics displayed changes depending on both the type of coarse aggregate and cement. Shape and morphological characteristics of the coarse aggregates like surface texture played significant role on the performance of fresh SCC. Mixes composed of gravel with smooth surface and spherical shape exhibited improved levels of the viscosity, flowability and passing ability of fresh SCC in comparison to crushed coarse aggregates with rough surfaces. Although the relative specific gravity and fineness of the cement influenced the characteristics some other factors can be responsible for the behavior of the SCC as well. Mixes composed of CEM V cements are appropriate for high flowability, passing ability and segregation resistance of SCC. The following mixes could be employed for achieving the associated qualities respectively; sulfate resistance cement+gravel mixes for applications that necessitate lower viscosity levels, CEM V+grey limestone mixes for the largest flowability, CEM V+gravel mixes for the best passing ability, and lastly CEM V+white limestone mixes for the best segregation resistance. <br/> <br/>Page(s): 239-247 Sun, 29 May 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/12471 Title: Mitigation of rutting in bituminous roads by use of waste polymeric packaging materials <br/> <br/>Authors: Jain, P K; Kumar, Shanta; Sengupta, J B <br/> <br/>Abstract: Rutting is caused by accumulation of permanent deformations caused by repeated applications of traffic loads and it is a stress controlled cyclic loading phenomenon. The process of deformation of bituminous surfacing is accelerated by increase of pavement temperature, reduction in stiffness of mix and increase in traffic loads. The aim of this paper is to report findings of study on increase in stiffness modulus of bituminous mixes by incorporation of waste polymeric packaging material (WPPM) to enhance pavement performance as well as to protect environment. This work presents studies on use of WPPM in road construction. Polymeric poly packs are used for packaging of milk for distribution to consumers and such bags after consumption of milk are thrown away. These used milk bags and other high density polyethylene (HDPE) based carry bags are used as additives in bituminous mixes. The optimum dose of these two types of WPPM for modification of bitumen and bitumen mix is investigated. Results reveal that optimum dose of WPPM is 0.3 to 0.4% by weight of bituminous mix. Higher dose lead to undesirably higher stiffness of mix. Rutting of bituminous mix can be reduced to 3.6 mm from a value of 16.2 mm after application of 20,000 cycles, by adding optimum quantity of WPPM in bituminous mix for road construction. Indirect tensile strength ratio further confirm potential of these mixes in prevention of moisture damage also, ultimately improvement of pavement performance, besides alleviating disposal problems of WPPM for clean and safe environment. <br/> <br/>Page(s): 233-238 Sun, 29 May 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/12470 Title: Production and characterisation of Cr-Si-Ni-Mo steel foams <br/> <br/>Authors: Mutlu, Ilven; Oktay, Enver <br/> <br/>Abstract: In this study, production of Cr-Si-Ni-Mo steel foams by space holder-water leaching technique in powder metallurgy is investigated. Cr-Si-Ni-Mo steel powders are mixed with different amounts of carbamide and then compacted at 180 MPa. Polyvinyl alcohol is used as a binder. The carbamide in the green compacts is removed by water leaching at room temperature. The foams having porosities ranging from 39 to 72 % are produced after sintering at temperatures between 1150 and 1250ºC and times of 30 and 60 min in H₂ atmosphere. Young’s modulus and compressive yield strength values of the steel foams are in the range of 0.20-5.21 GPa and 24-290 MPa, respectively. Increasing sintering temperature and sintering time enhanced the Young’s modulus and compressive yield strength of the foams. The relationship between the Young’s modulus and compressive yield strength with the relative density of the foams is found to obey a power law relation. <br/> <br/>Page(s): 227-232 Sun, 29 May 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/12469 Title: Preparation and characterization of cordierite powders by water-based sol-gel method <br/> <br/>Authors: Tang, Bin; Fang, YouWei; Zhang, ShuRen; Ning, HaiYan; Jing, ChunYu <br/> <br/>Abstract: Cordierite gel is synthesized by water-based sol-gel route, starting from basic magnesium carbonate and Al(NO₃)₃ inorganic solution dissolved in silica-ethanol sol. Crystallizing process of xerogels is confirmed by TG-DSC and X-ray diffraction. The μ-cordierite is formed firstly, then small amount of β-SiO₂ and Mg-Al spinel are identified, at the same time the sapphirine is formed through the chemical reactions from β-SiO₂ and Mg-Al spinel, and finally transformed to α-cordierite entirely. The obtained powders are analyzed by SEM and granularity analysis. The results show that more pure, fine and uniformly dispersed cordierite powders can be manufactured by water-based sol-gel method. The cordierite ceramics shown low dielectric constant (ε<5), low dielectric loss (tanδ<0.004) and low thermal expansion coefficient (α<1.85×10^-6/^oC). <br/> <br/>Page(s): 221-226 Sun, 29 May 2011 22:58:59 GMT