Similarities and differences of pumping conventional and self-compacting concrete

In Practice, Self-Compacting Concrete (SCC) is Considered as a Simple Extension of Conventional Vibrated Concrete (CVC) When Pumping is Concerned. the Same Equipment, Materials, Pumping Procedures and Guidelines Used for CVC Are Applied When Pumping SCC. on the Other Hand, It Has Been Clearly Shown that the Rheological Properties and the Mix Design of SCC Are Different Than CVC. Can the Same Pumping Principles Employed for CVC Be Applied for SCC? This Paper Compares the Some Published Results of Pumping of CVC with Those for SCC. a First Striking Difference between Pumping of CVC and SCC is the Flow Behaviour in the Pipes. the Flow of CVC is a Plug, Surrounded by a Lubricating Layer, While during the Flow of SCC, Part of the Concrete Volume itself is Sheared Inside the Pipe. as a Result, the Importance of Viscosity Increases in Case of SCC. Due to the Low Yield Stress of SCC, the Behaviour in Bends is Different, But Quite Complex to Study. Due to the Lower Content of Aggregate and Better Stability of SCC, as It is Less Prone to Internal Water Migration, Blocking is Estimated to Occur at Lower Frequency in Case of SCC. © RILEM 2010

Extension of the Reiner-Riwlin Equation to Determine Modified Bingham Parameters Measured in Coaxial Cylinders Rheometers

The Determination of the Exact Rheological Properties, in Fundamental Units, of Cementitious Materials Has Become Gradually a Necessary Step in the Domain of Concrete Science. Several Types of Rheometers and their Corresponding Transformation Equations Are Described in the Literature. in This Paper, the Reiner-Riwlin Transformation Equation, Valid for Coaxial Cylinders Rheometers, is Developed for the Modified Bingham Model, which is an Extension of the Bingham Model with a Second Order Term in the Shear Rate. the Established Transformation is Shown to Be Compatible with the Reiner-Riwlin Equation for the Bingham and Herschel-Bulkley Models. its Validation is Further Proven by Means of Numerical Simulations Applied on Experimental Data. the Yield Stress Values for the Three Rheological Models (Applied on the Same Experimental Data) Are Compared with the Yield Stress Calculated by Means of Slump Flow Values. Results Showed that the Modified Bingham Model Results in the Most Stable Yield Stress Values, Which Are Independent of the Non-Linear Behavior. © 2012 RILEM

Concrete mixing truck as a rheometer

Publisher's version (útgefin grein)An increasing interest has emerged in correlating the output of the concrete mixing truck to values obtained by rotational rheometers. The output of the former has usually been the hydraulic pressure needed to turn the drum. In such research, experimental errors can be higher than usual, which makes it harder to obtain confident relationships. To better understand the physical characteristics of the truck's Theological values, the above analysis is made by a series of computer simulations (i.e. with CFD). From this, it is evident that the slope H of the truck's pressure values depends both on the plastic viscosity mu as well as on the yield stress tau(0). However, for the intercept G of the truck's values, it is mostly dependent on the yield stress tau(0). In addition to this, both values H and G depend on volume of concrete in the truck as well as on density.The Icelandic Research Fund -RANNIS (grant numbers 163382-051,163382-052,163382-053) and Norcem AS (Heidelberg Cement Group)."Peer Reviewed

Analysis of shear rate inside a concrete truck mixer

In addition to the mixing energy applied to the fresh concrete (i.e. shearing during mixing), the shear history after mixing is also important. This applies especially to binder rich concretes like the different types of high performance concrete (HPC). With this in mind, the shear rate is analyzed inside a drum of a concrete truck mixer. The objective is to better understand the effect of transport of fresh concrete, from the ready mix plant to the building site. The analysis reveals the effect of different drum charge volume and drum rotational speed. Also, the effect of yield stress and plastic viscosity is investigated. The work shows that the shear rate decreases in an exponential manner with increasing drum charge volume. It is also shown that for a given drum speed, the shear rate decreases both with increasing plastic viscosity and yield stress.This work has been funded by the Icelandic Centre for Research - RANNIS [grant numbers 163382-051, 1006100202], Norcem AS (Heidelberg Cement Group) and ReadyMix Abu Dhabi."Peer Reviewed

Analysis of Norwegian Offshore Wind Power Production : Ranking wind farm locations using a composite index method

This thesis studies wind power production within the Norwegian Economic Zone, and analyzes the potential production of wind power farm locations outlined by the Norwegian Water Resource and Energy Directorate. Offshore wind farms have great potential as an energy source, but have high initial investment and maintenance costs, and finding the optimal locations for production is therefore essential. We use estimation data on offshore wind production, Norwegian energy consumption, and the filling degree of Norwegian hydropower plants. We perform a descriptive analysis, exploring how seasonal variations in wind power production relate to Norwegian electricity consumption, and how offshore wind can benefit Norwegian hydropower reservoirs. We find that in an average year, wind power production and electricity consumption will follow a similar seasonal cycle. The output potential of offshore wind power peaks during months with high electricity demand, which suggests that offshore wind is suited to Norwegian energy needs. Additionally, we find that wind power production and water levels in Norwegian reservoirs do not follow the same pattern. Water levels are at their lowest point during the spring, a period when the wind power output is still substantial. Therefore, we argue that offshore wind is a good complementary energy source for hydropower. To analyze the potential of the suggested locations we use three indicators that reflect the capability of the locations in a composite index. The index ranks the locations based on power output, stability, and correlation with Norway's electricity consumption. The three locations scoring the highest are "Sørlige Nordsjø 2", "Sørlige Nordsjø l " , and "Nordøyan - Ytre Vikna", all located in the southern half of Norway.nhhma

Localizing Global Solidarity: Humanitarian Aid in Lesvos

publishedVersio

The Norwegian maritime sector

The four papers in this thesis investigate corporate governance in family firms from different angles, with emphasis on industry and industry networks. I divide the industry networks into social and commercial networks, where social networks are measured by interlocking boards and commercial networks by investments in other firms in the same industry. Focus is on the governance structures in family firms, how industry and networks may be determinants of family ownership, and the effect of family ownership and strong industry networks on financial performance in certain industries (such as the maritime industry). Two of the papers are theoretical papers and two are empirical papers. The empirical papers are based on the same hand-collected dataset comprising 167 Norwegian listed companies from 1996-2005. The first paper - “Corporate Governance in Family firms” comprises a survey of the corporate governance literature on family firms, paying attention to the unique issues in the governance of these firms. I discuss different forms of ownership and how different agency contexts and business environments may suit family ownership better than other ownership structures. I also discuss how firms can reap the benefits of family ownership, by using a relational governance model, if there is an atmosphere of positive relationships, trust and shared visions. A relational governance model focuses on the social capital embedded in personal relations between owners, managers and board members. A contractual governance model, however, focuses on finding the optimal incentives in the relations between owners and managers, in addition to having greater focus on the monitoring role of the board. These two models may complement and supplement each other in a governance structure. The question is how these different governance models affect firms’ operations, decision-making, and competitiveness. The second paper - “The Effect of Industry Networks on Family Ownership” deals with possible effects of industry networks on the prevalence of family firms in different industries. I discuss how various networks can be determinants of family ownership, in addition to elements like incentives, monitoring, and altruism, as well as firm, industry and nation specific factors. I also discuss whether family firms can gain more from these industry networks than other firms due to a higher degree of ”thick trust”, strong owner-manager relations and the use of a relational governance structure. This paper proposes that strong social and commercial networks affect the number of family firms in an industry, as a result of the social capital embedded in these relations. Paper three - “Social and Commercial Networks as Determinants of Family Ownership - The Norwegian Shipping Industry” is an empirical paper testing whether industry networks are among the determinants of family ownership in the Norwegian shipping industry. The overall question is why family ownership is more prevalent in some industries, and which elements that influence this ownership structure. I focus on industry effects such as the number of firms in an industry and the social and commercial industry networks between firms. These are potential determinants of family ownership. I find that both industry and various industry networks have a significant and positive effect on family ownership in the shipping industry. The fourth paper - “Family Ownership, Networks and Financial Performance” takes up the question whether family ownership and various networks affect financial performance, measured by Tobin’s q and ROA lagged, or not. Earlier studies come to different conclusions regarding the relationship between family ownership and firm performance, which may be due to differences in the agency context of the studies. I add industry and industry networks as central variables to disentangle some of the contextual factors in this relationship. This paper argues that it is not necessarily the family ownership that affects performance, but how this ownership is used in a strategic manner. Establishing and using networks are seemingly a means of operation in some industries, sometimes with a positive effect on performance

Low Carbon Concrete Possibilities: EPD and Regulations in Northern Periphery and Arctic

Concrete is one of the most common building materials in the Northern Periphery and Arctic, and therefore we should pay attention to its quality while reducing its carbon footprint. The concrete industry has established many measures to limit greenhouse gas emissions from concrete, as stated in the environmental product declaration (EPD). The most significant contributor is cement (common dose between 250 and 600 kg per 1 m3 of concrete) in a concrete binder. Aside from the use of alternative fuels for cement production, new alternative materials for cement replacement are being sought. Those materials are called supplementary cementitious materials and mainly originate from industrial waste streams. Some of the materials are already standard and limited by the maximum allowed replacement, and some are new and still under investigation. The benefits and limitations of low-carbon concrete regulations in Norway, Sweden, Iceland, and Finland are demonstrated on three different concrete mixes in this article. The sorting of a reference mix and two low-carbon concrete mixes according to 4 different systems showed the informative character of the Icelandic system and the underestimation of possibilities for the carbon footprint of concrete in the Swedish classification system