Evaluation of the effect of sodium silicate addition to mine backfill, Gelfill − Part 1

In this paper, the mechanical properties of sodium silicate-fortified backfill, called Gelfill, were investigated by conducting a series of laboratory experiments. Two configurations were tested, i.e. Gelfill and cemented hydraulic fill (CHF). The Gelfill has an alkali activator such as sodium silicate in its materials in addition to primary materials of mine backfill which are tailings, water and binders. Large numbers of samples of Gelfill and CHF with various mixture designs were cast and cured for over 28 d. The mechanical properties of samples were investigated using uniaxial compression test, and the results were compared with those of reference samples made without sodium silicate. The test results indicated that the addition of an appropriate amount of an alkali activator such as sodium silicate can enhance the mechanical (uniaxial compressive strength) and physical (water retention) properties of backfill. The microstructure analysis conducted by mercury intrusion porosimetry (MIP) revealed that the addition of sodium silicate can modify the pore size distribution and total porosity of Gelfill, which can contribute to the better mechanical properties of Gelfill. It was also shown that the time and rate of drainage in the Gelfill specimens are less than those in CHF specimens made without sodium silicate. Finally, the study showed that the addition of sodium silicate can reduce the required setting time of mine backfill, which can contribute to increase mine production in accordance with the mine safety

Evaluation of the effect of sodium silicate addition to mine backfill, Gelfill – Part 2: Effects of mixing time and curing temperature

The effects of mixing time and curing temperature on the uniaxial compressive strength (UCS) and microstructure of cemented hydraulic fill (CHF) and sodium silicate-fortified backfill (Gelfill) were investigated in the laboratory. A series of CHF and Gelfill samples was mixed for time periods ranging from 5 min to 60 min and cured at temperatures ranging from 5 �Cto 50 �C for 7 d, 14 d or 28 d. Increasing the mixing time negatively influenced the UCS of Gelfill samples, but did not have a detectable effect on CHF samples. The curing temperature had a strong positive impact on the UCSs of both Gelfill and CHF. An elevated temperature caused rapid UCS development over the first 14 d of curing. Mercury intrusion porosimetry (MIP) indicated that the pore size distribution and total porosity of Gelfill were altered by curing temperature

Sometimes You Cannot Have It All: Party Switching and Affiliation Motivations as Substitutes

Existing research on when legislators switch parties reports inconsistent results about motivations for switching (e.g., office, ideology, and votes). I treat the motivations for party switching as substitutes and argue that many of the inconsistencies that persist can be explained by modelling the interactive effects between these motivations. For example, scholars differ in terms of whether they find that electoral considerations are an important determinant of party switching. The conflicting findings on the independent effects of electoral considerations are explained here by demonstrating that these effects are conditional on the level of office benefits a legislators enjoys, as well as the ideological distance between the legislator and party. More generally, the empirical analysis provides strong support for the substitution effect hypothesis. Thus, modelling interactive effects increases our understanding of party switching

Analysing constitutional reform in Britain: Insights from economic approaches

Over the last decade, the British state has been profoundly restructured. These changes challenge scholars to develop accounts capable of providing a unified analysis of the various reforms and of enabling their effects to be identified. While there is now a large literature on constitutional change in Britain, most of these studies focus on individual institutions and neglect the reforms’ collective nature and effects. To develop a more unified analysis of the reforms and their consequences, we need an account of what institutions are and of how they work. Economic analyses of institutions provide such an account, helping us to identify the common operating logics that underpin different institutions along with their effects. Insights from the economic approach to institutions are drawn on to explore how the constitutional reforms in Britain affect the distribution of decision-making authority and the nature of political accountability