Development of pervious concrete
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In many developed countries, the use of pervious concrete for the construction of pavements, car parks and driveways is becoming popular. In order to develop material specification for pervious concrete, it is necessary to conduct testing to evaluate the performance of this new type of high-performance concrete. In addition, carbon dioxide emission from Portland cement production is significant and contributes to global warming which leads to undesirable climate change. Therefore, it is necessary minimise the use of Portland cement in pervious concrete mixes by partially replacing the cement with industrial by-product, such as fly ash and slag which have been used successfully as supplementary cementitious materials in structural concrete mixes. The pervious concrete is produced by using conventional cementitious materials, aggregates, and water. This concrete is tested for its properties, such as density, porosity, compressive strength, water permeability and drying shrinkage. The most important property of pervious concrete is its water permeability. Currently, there is no standard experimental procedure to determine to this property. A method was therefore developed to determine the water permeability. Fly ash is used as a supplementary cementitious material to partially replace Portland cement in pervious concrete mixes up to 50% by weight. To improve the acceptance of pervious concrete, it is necessary to improve the surface texture. Due to the rough surface texture and bigger void content, it may be difficult for pervious concrete for wide acceptance by the construction industry. Therefore, fine textured pervious mortar is produced using cementitious materials, aggregate and water, and its properties are investigated. New type of pervious pavement, a combination of pervious concrete and pervious mortar, is developed and its properties are studied. Pervious concrete having density around 1800 kg/m3 shows the following properties, porosity 0.32 to 0.36, 28-day compressive strength between 5.7 MPa and 10.1 MPa, water permeability between 9.2 mm/s and 17.3 mm/s, and 56-day drying shrinkage between 470 and 600 microstrain. The properties of pervious mortar having 0.35 water/cement ratio with hand compaction are as follows; density of 1690 kg/m3, porosity of 0.34, 28-day compressive strength of 5.8 MPa, water permeability 2.6 mm/s, and 56-day drying shrinkage of 490 microstrain. Combination of pervious concrete and pervious mortar is tested in density and water permeability. The density is around 1750 kg/m3, while the water permeability between 2.3 mm/s and 3.0 mm/s. Further investigation on the development of this system to have adequate water permeability, strength and durability is recommended.
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