NISCAIR Online Periodicals Repository Collection: IJEMS Vol.19(5) [October 2012]

Sulphuric acid resistant ecofriendly concrete from geopolymerisation of blast furnace slag

Fri, 28 Sep 2012 22:58:59 GMT

Title: Sulphuric acid resistant ecofriendly concrete from geopolymerisation of blast furnace slag

Authors: Rajamane, N P; Nataraja, M C; Lakshmanan, N; Dattatreya, J K; Sabitha, D

Abstract: In this study, geopolymer is prepared from ‘ground granulated blast furnace slag’ (GGBS)–a powder from grinding the by-product of slag waste from blast furnace of steel plants. For comparison, conventional cement, Portland pozzolana cement (PPC) containing fly ash was considered. To achieve simultaneous acidic and sulphate attack, sulphuric acid is used for durability studies. The test data indicate that on exposure to 2% and 10% sulphuric acids, the losses in weight, thickness and strength of geopolymer concrete (GPC) are significantly much less than those for Portland pozzolana cement concrete (PPCC). The GPCs have inorganic polymers of alumino-silicates as binder, generally without any free lime. Therefore, GPCs resist acid attack better than free lime containing conventional concretes containing Portland cement. The binding action in GPC is through geopolymerisation of GGBS using alkaline activator solution (AAS) made of sodium hydroxide and sodium silicate solutions. The geopolymer eliminates use of Portland cement in structural concretes by utilizing the industrial by-product GGBS, thereby reducing considerably the carbon footprint measured by ‘embodied energy’ and ‘embodied carbon’, i.e., ‘CO₂e emission’ of concrete.

Page(s): 357-367

Effect of environments on the thermal properties of epoxy adhesives modified with nano- and micro-particles for in-situ timber bonding

Fri, 28 Sep 2012 22:58:59 GMT

Title: Effect of environments on the thermal properties of epoxy adhesives modified with nano- and micro-particles for in-situ timber bonding

Authors: Ahmad, Z; Ansell, M P; Smedley, D; Tahir, P Md

Abstract: This paper reports the investigation made on the effect of nano- and micro-particles additions on the thermal properties of epoxy based adhesives when exposed to different environmental conditions. The thermal behaviors of the adhesives are measured using dynamic mechanical thermal analysis (DMTA) following exposure to different temperatures and humidities which include temperatures of 20, 30 and 50°C, relative humidities of 65, 75 and 95% RH and soaking in water at 20°C and placed in the oven at 50°C. The dynamic thermal properties reported include storage modulus and loss modulus, the loss tangent and the glass transition temperature, T_g. For nano- and micro-particles filled adhesives, the glass transition temperature increases with increase in temperature even though the adhesives are subjected to high humidity and this is due to further cross-linking. The results show that room temperature cured epoxies are only partially cured at room temperature.

Page(s): 343-356

Composition study of FePt nanoparticles synthesized from modified polyol process

Fri, 28 Sep 2012 22:58:59 GMT

Title: Composition study of FePt nanoparticles synthesized from modified polyol process

Authors: Chokprasombat, K; Harding, P; Sirisathitkul, C; Muthitamongkol, P; Pinitsoontorn, S

Abstract: Five different conditions for modified polyol processes using iron(III) acetylacetonate and platinum(II) acetylacetonate as starting materials reveal significantly different products in terms of composition. The initial Fe:Pt molar ratio is not retained in the final products and Pt-rich nanoparticles are obtained from 1:1 molar ratio of Fe:Pt sources. The imbalance between Fe and Pt indicate that the nanoparticles formation can be explained by the heterocoagulation mechanism rather than the binary nucleation model. The increase in refluxing time and initial Fe:Pt molar ratio improved the amount of Fe in nanoparticles. However, the highest molar ratio of 3:1 apparently affected the uniformity of particles. The co-existence of iron oxide and Pt-rich nanoparticles is clearly evident in the case of 3:1 molar ratio combined with 1,2 hexadecanediol as a reducing agent.

Page(s): 338-342

Polyelectrolyte hydrogels of chitosan and polyacrylamide: A comparison of electroactive characteristics

Fri, 28 Sep 2012 22:58:59 GMT

Title: Polyelectrolyte hydrogels of chitosan and polyacrylamide: A comparison of electroactive characteristics

Authors: Shamsudeen, Rahna K; Jayakumari, V G; Rajeswari, R; Mukundan, T

Abstract: In this paper, studies on polyelectrolyte hydrogels of both anionic and cationic type are reported. Partially hydrolysed polyacrylamide-polyvinyl alcohol interpenetrating polymer (IPN) has been synthesized as the anionic hydrogel and chitosan-polyvinyl alcohol interpenetrating polymers have been synthesized as the cationic one, both through a simultaneous IPN method. In both cases, the crosslink densities are varied and investigated for their swelling behaviour and rheological properties. The stimulus sensitivity of the hydrogels is determined by subjecting them to applied electric fields. The responses of the various hydrogels are correlated with the shear moduli, the crosslink densities and the swelling behaviour. An interesting observation of simultaneous bending of multiple gel slabs in different directions upon the application of the electric field is also reported.

Page(s): 331-337