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.
Laboratory evaluation of permeability and strength of polymer-modified pervious concrete
Abstract Pervious concrete has been increasingly used to reduce the amount of runoff water and improve the water quality near pavements and parking lots. However, due to the significantly reduced strength associated with the high porosity, pervious concrete mixtures currently cannot be used in highway pavement structures. A laboratory experiment was conducted in this study to improve the strength properties of pervious concrete through the incorporation of latex polymer. This study focused on the balance between permeability and strength properties of polymer-modified pervious concrete (PMPC). In addition to latex, natural sand and fiber were included to enhance the strength properties of pervious concrete. The test results indicate that it was possible to produce pervious concrete mixture with acceptable permeability and strength through the combination of latex and sand.
PREDICTING THE ABSORPTION OF OPEN WEAVE TEXTILES AND MICRO-PERFORATED MEMBRANES BACKED BY AN AIR SPACE
Abstract Although theories for both membrane absorbers and micro-perforated plate absorbers have been well developed, it appears that no theory has been given for their combination, such as a glass-fibre textile or a micro-perforated membrane mounted over an airtight cavity. This paper presents a theoretical method for predicting the absorption of such a structure. The basic idea of the theory is to regard an open weave textile or a micro-perforated membrane as a parallel connection of the membrane and apertures. The predictions for both normal and random incidence have shown very good agreement with measurements. It has also been demonstrated that the absorption performance of such structures can be very high. Typically, with appropriate parameters the absorption coefficient of a glass-fibre textile or a micro-perforated membrane mounted at 100 mm from a rigid wall can exceed 0·4 over 3–4 octaves. With two layers of the material over the same total air space of 100 mm this range can extend to 4–5 octaves.