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Quality and trueness of results received from measurements are very important for all involved parties, producers and consumers as well; for instance, if the results were used for acceptance of a product within a labeling procedure. Based on an inter-laboratory study with many German, European and US-American laboratories an extemal quality assurance System for the analysis of VOC emitting from products or the measurement in indoor air should be implemented (financed by the German Federal Environmental Agency).
A focus was set on the emission test chamber experiments and the connected analytical procedure. VOC have a dominating influence when applying the German AgBB scheme for health evaluation of building products.
Therefore it is necessary to ensure that the results between the testing laboratories are comparable. The successful participation to such round robin tests is offen essential for the acceptance of results given by an analytical laboratory.
The labelling of construction products or building materials as “low-emitting” is based on measurements using third-party emission test chambers. Unfortunately there is no method to validate the performance of such test chamber measurements. This might give a Variation of results when testing one material at different laboratories. Therefore it is necessary to hold round robin tests as part of the quality management System to ensure comparable results.
A research project financed by the Federal Environmental Agency focused on the development of an external quality management System for the detection of relevant Chemical compounds from products and in ambient air. The project was structured in four phases (Horn et al., 2009 and 2011; Wilke et al., 2009a) This paper shows results of the fourth phase of the project, which was an inter-laboratory study for VOC-emission testing by means of emission test chambers.
Wood and wood products are often used as construction material for buildings and even more for furniture and indoor decoration. Therefore Chemical emissions from wood have an influence on the indoor air quality. A research project financed by the Federal Environmental Agency focused on VOC emissions from oriented Strand boards (OSB) and also from plywood made from pine and spruce (Wilke et al., 2011a). This paper shows results of the plywood testing because only little information is available about plywood emission behaviour and its impact on indoor air quality.
The fire behaviour of composites clearly differs in comparison to polymers. Even though fibres and inorganic particles may be inert with respect to pyrolysis, they are clearly not with respect to fire behaviour. They change heat absorption and transfer within the Condensed phase, the melt flow/dripping behaviour of pyrolysing melts, the amount and properties of the fire residue and so on. Flame retardancy concepts tailored to composites are needed. Furthermore tasks that are specific for composites such as the structural integrity in fire get into the focus. Thus understanding of fire behaviour and flame retardancy mechanisms in composites is a key for target-oriented future development. The field is illuminated by Spotlights on different length scales. The examples are taken from different projects carried out in the group of the authors in the recent years. Flame retardancy mechanisms in nanocomposites are discussed, advanced halogen-free flame retardants for carbon and glass fibre composites presented as well as an approach to mechanical intermediate scale testing of carbon fibre composites under fire.
Wann ist es sinnvoll ein Biozid in ein synthetisches Material einzubringen? Wenn dadurch ein Problem gelöst wird. Deshalb sollte bei jeder Versuchsplanung die Frage stehen: Was ist das Problem, das man durch Biozieinsatz lösen will? Wie kann es im Laborversuch dargestellt werden? Konnte der Laborversuch zeigen, dass bei Biozideinsatz das Problem kleiner wird, beziehungsweise nicht mehr existiert? Je höher die Teststufe ist, umso mehr muss der Prüfablauf auf die Praxisbedingungen in der Gebrauchsphase des biozidhaltigen Erzeugnisses abgestimmt werden. Auf Stufe 1 werden in der Regel einzelne Wirkstoffe getestet. Ziel ist, die prinzipielle Wirksamkeit nachzuweisen, um die Ergebnisse für die Zulassung auf die Positivliste biozider Wirkstoffe der Biozidrichtlinie einzureichen. Während auf Stufe 1 bereits Normmethoden unter Einbeziehung einer relevanten Materialmatrix angewendet oder für die Fragestellung adaptiert werden können, ist dies für Stufe 2 oftmals nicht gegeben. Stufe 2 zeichnet sich durch Prüfmethodik mit praxisrelevanten Belastungen zur zeitraffenden Alterung des Biozids in seiner Materialmatrix aus. Hier stellt sich auch die Frage zur Langzeitwirksamkeit. Anstelle eines einzelnen Wirkstoffs wird oftmals ein Gemisch verschiedener Wirkstoffe und zusätzlichen Additiven, die wiederum Einfluss auf beispielsweise die Verteilbarkeit, Stabilität und Bioverfügbarkeit haben können. Es wird also kein Wirkstoff, sondern ein Biozidprodukt geprüft. In dem Biozidprodukt dürfen aber nur Wirkstoffe eingesetzt werden, die im Rahmen der Biozidrichtlinie bereits zugelassen sind und auf der Positivliste zu finden sind. Stufe 3 wird diskutiert im Zusammenhang mit Biozidprodukten mit Außeneffekt. Sie beschäftigt sich mit dem Nachweis von Vorteilen durch die Biozidnutzung. Hier gilt es den Verbraucher- und Umweltschutz gegen den Nutzen der möglichen Wertschöpfung oder auch den Gesundheitsschutz durch Biozideinsatz abzuwägen.
The cement and concrete market in East, Central and Southern Africa is highly fragmented. The concrete industry in this area consists of multiple parties, including producers and suppliers of construction materials, formal and informal contractors, engineers and architects, unions of trades persons and workmen, governmental bodies and formal institutions of research and education. All these institutions mostly do not interact adequately, which makes building with cementitious materials susceptible to damage and failures. Completely opposed to the situation in Europe or North America, cement in Africa is often unaffordable, while manpower is cheap, which results in a questionable economisation of cement. Typically, there is not sufficient awareness of methods to sensibly reducing the cement content in concrete or replace Ordinary Portland Cement by adequate alternative materials. Research activities in this field of technology are often missing completely. Only few countries in the area, such as South Africa, are exempted from these issues.
This paper presents the SPIN project, which is a joint project of a consortium of 8 African and 3 European partners within the ACP Science and Technology Programme. The project is funded by the EC and ACP Secretariat is the project body. The main objective of the current project is to strengthen the cement and concrete industry in the East and Central African regions. The project shall generate reasonable solution strategies to implement clean, safe and sustainable cement and concrete technology on the African continent, including general and specific guidelines for sensible application. Furthermore it shall be the kick-off for future projects, research activities and the world-wide expansion of a European-African network.
The paper addresses special problems the cement and concrete market in Eastern, Central and Southern African countries has to face. Several options are presented in detail, which shall help overcoming the current situation. Customized solutions for the African market include rational methods for reducing the amount of cement used and the replacement of Ordinary Portland Cement with cheaper alternatives. The use of recycled concrete through a new and economically effective method, as well as the opportunity of using locally available resources is also discussed.
Concrete technology was exposed to a rapid development during the last three decades. For the longest time in its history, concrete was considered as a three component System consisting of aggregates, which are bound by the hardened cement paste consisting of hydrated cement. Traditionally, the only way of adjusting the consistency of concrete was using well adjusted aggregates and grading curves and adding excess water to the concrete, accepting that the latter in return reduces strength and durability. During the last three decades, however, concrete has developed further from a three component System towards an (at least) five component system, since the use of mineral additions and Chemical admixtures has become state of the art. Both components are able to enhance the workability, the compactability, and the density of the microstructure with effects on strength, ductility and durability, while cement can be saved in parallel. Due to reasonable use of admixtures and additions, concrete can be designed to match mechanically high performance specifications. Traditionally, cement paste was considered the weakest component in concrete. Flowever, in modern concrete a good paste composition can yield highest performance, passing the role of the mechanical bottleneck towards the aggregates.
Today polycarboxylate ether based superplasticizer (PCE) is commonly used in concrete technology when high flow properties and water reduction are specified. The ionic strength of the polymers’ backbones determines the adsorption behaviour of polymers on clinker and early hydration products. The amount of required polymers for specified flow properties and the performance over the time of casting is thus determined by the molecular structure of the superplasticizer. The time depending consumption of polycarboxylate ether polymers strongly affects the reaction of aluminates and sulphate ions as well as the hydration process in general. Hence, the choice of polymers for particular flow properties greatly affects the very early properties of cementitious materials such as setting, heat evolution and autogenous deformations.
In order to better understand how PCEs influence the early properties, mixes from cement, limestone filler, viscosity modifying agent and water were varied with a high and a low charge density superplasticizer in differing amounts. Results are presented from measurements with an automatic Vicat device, an isothermal heat flow calorimeter, and shrinkage cones. Tests were conducted at 5, 20, and 30 °C.
It is shown that in presence of PCE the final set correlates well with the inflexion point of the heat flow curve, which emphasises the interrelation between C-S-H formation and setting. No such clear correlation can be found for the initial set, which is attributed to the fact that the initial set is rather a rheological than a structural phenomenon, so that other effects overlap with C-S-H formation. The results demonstrate that for a given polymer concentration low charge density polymers yield earlier setting than high charge polymers. However, this influence is overridden by the influence of the total amount of polymers in a cementitious system. Since PCE is typically added according to rheological specifications, and low charge PCE typically requires higher amounts of polymers than high charge PCE for comparable flow performance, low charge PCE retards setting more than high charge PCE.
The paper furthermore points out that there is no significant influence of the polymer type or amount on the early deformations. Since type and amount strongly affect the hydration, it is demonstrated that early setting causes higher strain after the final set. It is hence concluded that higher PCE solid contents reduce the risk of early cracks that occur at time of setting, when a solid structure has already been formed but without resistance against cracks yet.