APPLICATION OF PERVIOUS CONCRETE IN ROAD CONSTRUCTION
This paper presents an overview of the properties of porous concrete, and the advantages of its use in pavement structures. Two mixtures of pervious concrete and a reference concrete mixture commonly used for concrete pavements are prepared and their properties compared: consistency, compressive and flexural strength, porosity and density, dynamic modulus of elasticity, as well as permeability. The possibility of their application in concrete pavements is estimated in accordance with the requirements given in General technical conditions for roadworks. Mixture with a small amount of cement and addition of superplasticizer did not meet minimum porosity and permeability required for pervious concrete. In contrast, a mixture with a higher amount of cement and without the addition of superplasticizer was evaluated as pervious one, but does not have a compressive strength required for road construction. Therefore, it is necessary to direct further research towards improving the compressive strength of mixtures of pervious concrete.
Acoustic absorption modeling of porous concrete considering the gradation and shape of aggregates and void ratio
The results of acoustic absorption modeling of porous concrete considering the gradation and shape of aggregates and void ratio are presented. To model the void texture of porous concrete, the multi-layered micro-perforated rigid panel model considering air gaps [1,2] is adopted. The parameters used in this acoustic absorption modeling are determined by a geometrical and experimental approach considering the gradation and shape of aggregates and void ratio. The predicted acoustic absorption spectra are compared with experimental results to verify the proposed acoustic absorption modeling approach. Finally, a parametric study is conducted to investigate the influence of design factors on the acoustic absorption properties of porous concrete.
Design of concrete mixes
The article describes a method of mix design which recently has been introduced in Sweden. The method has wide applicability as it can be used for both concrete and mortar, with great variations in constituents and properties. The method is based on an extensive investigation in which a new relationship is put forward between the percentage by volume of aggregate and the water/cement ratio, given constant consistence and grading.Guidance is given how local materials and standards can be taken into consideration, if the method is used outside Sweden.There has been a computer programme made for the mix disign method.RésuméOn décrit une méthode de calcul du dosage récemment introduite en Suède, qui peut s’appliquer aussi bein au béton qu’au mortier, même avec de grandes variations dans les constituants et dans les propriétś. La méthode repose sur une étude étendue qui a permis d’établir une nouvelle relation entre le pourcentage en volume de l’agrégat et le rapport eau/ciment, la consistance et la granulométrie étant constantes.La méthode comprend 5 étapes, 1. Une relation entre le rapport eau-air/ciment et la résistance sert à choisir le rapport eau-air/ciment approprié. 2. On choisit la consistance de façon à satisfaire aux conditions de mise en place. 3. La teneur en air est soit estimée, soit choisie (lorsqu’on se sert d’agents entraîneurs d’air). 4. En ce qui concerne les agrégats, on choisit d’abord deux points sur la courbe granulométrique élaborée pour plusieurs types d’agrégat, à savoir la dimension maximale des gros agrégats, dmax, et le pourcentage de tamisat de 4 mm, Y0. On choisit alors le gravier et le gros agrégat et leurs proportions mutuelles sont calculées de telle sorte qu’on obtienne Y0% de la combinaison des agrégats à 4 mm. On calcule ensuite le module de finesse de la combinaison d’agrégat. 5. On se sert de la relation entre le pourcentage en volume de l’agrégat et le rapport eau/ciment pour déterminer la composition du mélange de telle sorte qu’on obtienne la consistance et le rapport eau-air/ciment souhaité. Enfin, on indique comment on peut tenir compte des matériaux locaux et des normes lorsque la méthode est utilisée hors de Suède.Un programme de calculateur électronique a été établi pour l’emploi de cette méthode.