Strength prediction and durability performance of concrete containing coal bottom ash as supplementary cementitious material under aggressive environment

Strength prediction and durability of concrete under aggressive environment requires serious attention for all kind of significant concrete structures. However, concrete built with Ordinary Portland Cement (OPC), when exposed to the aggressive environment tends to deteriorate much faster than their projected service life. Therefore, Supplementary Cementitious Material (SCM) need to be introduced to improve the strength and durability performance of concrete. Besides that, prediction of concrete compressive strength is also an important aspect for the safety and quality control of concrete structures. Thus, this study aims to evaluate strength and durability performance of concrete containing Coal Bottom Ash (CBA) as a SCM and to develop empirical equation to predict compressive strength of concrete under normal as well as in aggressive environment. CBA was considered as SCM because it is a huge waste that produced by a coal-based power plants, which creates environmental problems for the global society. Initially, raw CBA was grinded for various periods, to get different particle fineness, then CBA was incorporated as replacement of OPC in concrete at various percentages 10%, 20% and 30% by weight of cement. The optimum percentage replacement and suitable grinding period were determined based on concrete strength performances and it was found that 10% proportion of CBA gives the optimum results at the age of 28 days. Next, the performance of concrete containing 10% CBA was further evaluated in terms of compressive strength, change in weight and degree of damage under aggressive environment such as 5% sodium sulphate (Na2SO4), 5% sodium chloride (NaCl), combination of both (5%Na2SO4+5%NaCl) and seawater at the exposure period of 28, 56, 90 and 180 days. Additionally, microstructural changes in concrete due to aggressive environment were also assessed through Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) techniques. Besides that, the durability performance of concrete containing CBA were also evaluated using Rapid Chloride Permeability Test (RCPT). Moreover, influence of CBA on the drying shrinkage of concrete was also evaluated up to age of 180 days. The experimental results reveal that Control Mix (CM) delivers worst performance when exposed to seawater. However, the incorporation of 10% CBA in concrete enhances its strength performance under seawater exposure. Strength performance of concrete containing 10% CBA exhibits satisfactory in all aggressive environment conditions except 5% NaCl. It was also evaluated that concrete containing 10% CBA exhibits around 45.4% reduction in chloride penetration as compared to CM at 180 days, which indicated its potentiality as durable SCM. Besides that, it was experimentally and theoretically verified that the proposed Bolomey’s Modified Equation (BME) can be used for the prediction of compressive strength of concrete containing ground CBA exposed to normal as well as aggressive environment that particularly represents the marine environment. Hence, this study declared 10% ground CBA as optimum that can be used for future research

Explaining Manipur’s breakdown and Mizoram’s peace: the state and identities in north east India

Material from North East India provides clues to explain both state breakdown as well as its avoidance. They point to the particular historical trajectory of interaction of state-making leaders and other social forces, and the divergent authority structure that took shape, as underpinning this difference. In Manipur, where social forces retained their authority, the state’s autonomy was compromised. This affected its capacity, including that to resolve group conflicts. Here powerful social forces politicized their narrow identities to capture state power, leading to competitive mobilisation and conflicts. State’s poor capacity has facilitated frequent breakdown in Manipur. In Mizoram, where state-making leaders managed to incorporate other social forces within their authority structure, state autonomy was enhanced. This has helped enhance state capacity and its ability to resolve conflicts. Crucial to this dynamic in Mizoram was the role of state-making leaders inventing and mobilising an overarching and inclusive identity to counter entrenched social forces. This has helped with social cohesion

Computationally synthesised inorganic and organometallic complexes : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Albany, New Zealand

Catalytic aromatic ring C–H bond functionalisations by transition metal cyclometallation reactions are important for organic transformation reactions. The cyclometallated product, which contains a new metal–carbon bond is formed as a consequence of different types of carbon–hydrogen····metal (C–H····M) interactions. These C–H···M interactions have been known as anagostic, preagostic and agostic interactions. By nature, the anagostic interaction has mainly electrostatic components, the preagostic interaction has electrostatic components with some back-bonding from metal to C–H antibonding orbital involved and the agostic interaction has mainly covalent components when the C–H bond donates electron density to the partially occupied metal centre. Prior to the current thesis work, an in-depth study that addresses the influence of steric and electronic factors on the anagostic, preagostic and agostic carbon–hydrogen····metal interaction was missing. In this thesis, the influence of both the steric and electronic factors on the anagostic, preagostic and agostic C–H···M interactions has been studied. It is seen that the electronic and steric influences play differently for different ligand systems as with the flexible tetralone ligand, a maximum of steric and electronic influence results into another type of anagostic interaction named as the 'C-anagostic' interaction. It is also seen that a stronger steric and electronic effect can trigger agostic covalency at the anagostic stage of the reaction. The inflexible ligand ensures the short anagostic approach, which has some back-bonding character and the nature of the interaction lies into the preagostic category. Finally, the aromatic ring agostic interactions have more complexity as new donations named as 'syndetic' from C–C pi bond to metal antibonding orbitals were recognised which shares the same antibonding acceptor orbitals as the agostic donation does. The recognition of new bonding situations in C–H····M interactions can have significant implications for C–H bond functionalisation reactions

Is There Seasonality in Pakistan’s Merchandise Exports and Imports? The Univariate Modelling Approach

This paper investigates the existence of seasonal patterns in the quarterly merchandise export and import data of Pakistan from 1982: 1 to 2002: 1. Unit root tests are applied to determine whether the seasonal component in each variable exhibits stochastic non-stationarity. Deterministic and stochastic effects are isolated and quantified. Few alternate DGP specifications are identified, fitted and tested for their outof- sample forecasting performance. A tentative finding is that deterministic effects are relatively more important than stochastic ones. However, integrated models, i.e., ARIMA, mixed ARIMA, and ARIMA-GARCH, outperform deterministic models with respect to forecasting