The continued retreat of non-profit housing providers in the Netherlands

After the abolishment of object subsidies for housing construction and renovation in the mid 1990s, Dutch housing associations, the main non-profit housing providers in the country, heavily relied on market activities, such as selling homes to owner occupiers, to generate income for their social activities and to contribute to urban development policies. This worked well, which was one of the main reasons that these housing providers could adopt a wide field of operations, including not only the management and development of affordable housing for low-income groups, but also housing in other market segments, plus activities regarding care, welfare, local economy, employment and education. Recent economic and political developments, however, have caused housing associations to return on this path. Central in this paper is a research among Dutch housing associations about their values, strategic positioning and strategies. The research was executed in two waves (conducted in 2010/2011 and in 2013/2014, respectively), each consisting of a panel survey and interviews with selected panellists. This paper presents the results of the second wave. It is expected that after the first wave of the research, new regulations, such as the national implementation of European rules on state support and the introduction of a new property tax, have resulted in a further retreat from non-social housing activities. The analysis shows that this is indeed the case, but that the main shifts in priorities have not taken place directly after the credit crunch, but in later years.     

Analysis of cross-country variations in the depth of European mortgage markets

To date, quantitative analysis on the depth of mortgage markets across a broad set of countries has been very limited. This paper uses a rich and balanced data set on 31 European countries to investigate the cross-country variations in the depth of mortgage markets during the period 2005–2012. The present paper might be accepted as the updated and enriched version of existing research for the European region in terms of the coverage of countries, historical data and the empirical analyses. Our empirical findings reveal that developed countries have sizeable residential mortgage markets and this is mainly associated with higher urbanization rates and stronger legal rights. One of the most notable results of this study is that, statistical significance of explanatory variables in modeling the depth of the mortgage markets depends heavily on both the variables, countries (regions) included in the models and the regression methodology used. Hence, we argue that strong conclusions based on such analyses should be avoided and the findings of previous research on the variations of the depth of mortgage markets should be carefully evaluated.     

Effect of a commercial dispersion of multi walled carbon nanotubes on the hydration of an oil well cementing paste

This work studies the influence of a commercial dispersion of multi wall carbon nanotubes (MWCNT) on the hydration of a class G cement paste, at room and elevated down-hole temperatures. The MWCNT dispersion was produced with a solids concentration of 3.0 % by mass and an anionic surfactant as dispersing agent. Cement pastes with water-to-cement ratio of 0.45 and additions of solid MWCNT by mass of cement up to 0.50 % were studied. Isothermal calorimetry results showed a clear retardation of the hydration of cement caused by the surfactant contained in the MWCNT dispersion. Nevertheless, thermogravimetric evaluations showed that once the hydration reaction resumed, the retardation effect of the surfactant did not have a negative impact on the amount of hydration products precipitated. It was concluded that the commercial MWCNT dispersion presents a good potential to be applied in oil well cement pastes.     

A simplified method for the determination of vertically loaded pile-soil interface parameters in layered soil based on FLAC<Superscript>3D</Superscript>

The numerical analysis of pile-soil interaction commonly requires a lot of trial works to determine the interface parameters and the accuracy cannot be ensured normally. Considering this, this paper first conducts a sensitivity analysis to figure out the influence of interface parameters on the bearing behavior of a single pile in sand. Then, a simplified method for the determination of pile-soil interface parameters in layered soil is proposed based on the parameter studies. Finally, a filed loading test is used for the validation of the simplified method, and the calculated results agree well with the monitoring data. In general, the simplified method proposed in this paper works with higher accuracy and consumes less time compared with the traditional trial works, especially on the determinations of interfacial cohesive and interfacial friction angle.     

Design and analyses of open-ended pipe piles in cohesionless soils

Large open-ended pipe pile has been found to be advantageous for use in transportation projects. The current design method, however, is not adequately developed. To close this practice gap, this paper first summarized different design methods for open-ended pipe piles in sandy soils. A major factor for all the design codes is to properly account for the formation and effects of soil plug. The comparison indicates that there is a large variation in the base capacity evaluation among different methods due to the complex behaviors of soil plug. To close the knowledge gap, discrete element method (DEM) was used to simulate the soil plugging process and provide insight on the plugging mechanism. The simulation results show that the arching effect significantly increases the internal unit shear resistance along pipe piles. The porosity distribution and particle contact force distribution from DEM model indicate a large stress concentration occurs at the bottom of the soil plug. Besides, nearly 90% of the plug resistance is provided by the bottom half portion of the soil column. The soil-pile friction coefficient has a significant effect on the magnitude of plug resistance, with the major transition occurred for friction coefficient between 0.3 and 0.4.     

Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste

In this experimental study, carbon nanotubes (CNTs) and carbon nanofibers (CNFs) were dispersed by intensive sonication in water in the presence of superplasticizer and subsequently mixed with Portland cement with water/ cement ratios varying between 0.3 and 0.4. The autogenous shrinkage in the fresh stage was investigated. The CNTs and CNFs were characterized by high resolution scanning electron microscopy (SEM) and the hydrated pastes were studied by X-ray diffraction and SEM. The results showed a reduction of the autogenous shrinkage by 50% for pastes containing small amounts (0.01 wt%) of nanomaterials. Higher additions appeared to be less effective. The highest reduction of shrinkage was observed for carbon nanofibers which were long, rather straight and had diameters of around 200 nm. The result showed that the addition of nanomaterials accelerated the hydration processes especially in the early stages of hydration. The effect was the most pronounced in the case of functionalized nanotubes. The proposed mechanism resulting in the reduction of the autogenous shrinkage was a combination of nano-reinforcing effects, alterations of hydration and microstructure of the hydrated matrix.     

Spluma,Zoning and Effective Land Use Management in South Africa

For the first time, South Africa has a single national piece of legislation, the Spatial Planning and Land Use Management Act, 2013, that creates an overarching framework for spatial planning, policy and land use management for the entire country, including rural and informal settlements. Spatial plans linked to zoning schemes are at the heart of this planning system. However, zoning as a land use management tool has been intensely criticised as being exclusionary and socially, economically and environmentally unsustainable. Given that the purpose of the new legislation is to create equitable and sustainable development, this paper questions whether zoning is indeed the most suitable land use management tool in South Africa. The paper briefly outlines the requirements of the new act and then evaluates the usefulness of various forms of land use management such as land use zoning, performance zoning, form-based control and discretionary systems in the South African context. Drawing on the strengths of some of the alternative land use management systems, proposals are made for a more suitable land use management system for South Africa that could have applicability in other countries with a similar colonial history.     

A Spatial Perspective of the Patterns and Characteristics of Main- and Substream Migration to the Western Cape,South Africa

This article provides a contemporary spatial perspective of patterns and trends in migration to the Western Cape during the period 2001 to 2011 and contributes an important new perspective on one of the dominant migration streams in South Africa. It applies the concepts of mainstream and substream migration from the differential urbanisation model to analyse characteristics and patterns normally hidden by aggregated migration data. The findings confirm the continuation of strong primary migration streams between the Eastern Cape and municipalities in the Western Cape driven mainly by productionism. These migrants are mostly unmarried, young (25–29 years), mostly unemployed or not economically active, with low incomes. A significant proportion (31.3 %) end up living in informal dwellings in backyards or informal settlements largely concentrated in the provincial primary city, Cape Town. A smaller but prominent substream of migrants to the province consists of affluent, highly skilled, mostly married migrants from other metropolitan cities in South Africa, many from Gauteng. These migrants are driven by environmentalism, and favour Cape Town and adjacent municipalities as their destination—particularly those areas along the south coast of the province containing intermediate-size cities. These identified migration patterns and characteristics hold important development implications at both provincial and municipal levels.