Evaluation of Strengths and Permeability of Pervious Concrete

Abstract

Our cities are being covered with building and road which is made up of air proof concrete. Because of the lack of water permeability of the concrete pavement, the rainwater is not feltered underground. In addition to that normal concrete absorb a heat so that temperature in the large cities increases. For that pervious concrete is a system which provides a solution for these. In pervious concrete we intentionally allow water to pass through it by creating open structure. To improve the acceptance of pervious concrete, it is necessary to improve the strength of pervious concrete. Due to the low strength and bigger void content, it may be difficult for pervious concrete for wide acceptance by construction industry. The im- portance of void content in pervious concrete cannot be overstated. Too much void content leads to low strength while not enough void and permeability sufers and the concrete can hardly be called pervious. Proper design of pervious concrete is therefore largely dependent on finding the balance between strength and water permeability. The large interconnected voids in the material is achieved by using a near single sized aggregate of relatively large grains. The packing of this coarse aggregate leads to large voids due to the similar sizes of the grains. In the present context, research on pervious concrete has started in last 20 years mainly in Europe, US and Australia. In India only few projects have been taken up and suficient literature details are not available in the form of published information in this area in journals/conference proceedings. It is imperative to study properties and feasibility to use this new and emerging area of concrete and find suitability of pervious concrete and other material and also help in laying down procedures and guidelines according to our codes and material specification and practices. The main objective of this investigation is to increase the strength of pervious concrete by producing various mix design. In pervious concrete fine aggregate is not normally used but our aim is to use some percentage of sand to improve the strength of pervious concrete. To further improve the strength of pervious concrete addition of cementatious material such as y ash and silica fume is done. The main properties studied are compressive strength, density, permeability, exural strength and split tensile strength. For the measurement of permeability test set up is developed. The falling head test method was used to find out permeability coefficient. Pervious concrete is produced with different size of aggregate. After various com- bination of aggregate size pervious concrete produced with mix size aggregate having more compressive strength than single size of aggregate. For pervious concrete as the density increases compressive strength increases while permeability decreases. Dur- ing experimental investigation results shows that pervious concrete having density around 1800 kg/m3 to 2250 kg/m3, compressive strength between 8 to 14 MPa and permeability between 11 to 21 mm/sec. Pervious concrete having sand content improved its compressive strength but reduce its permeability in large extent. Pervious concrete having sand content 5% and 15%, increase its compressive strength around 25% and 50% respectively and decrease it's permeability around 75%. Pervious concrete with y ash and silica fume improved the properties of it. Fly ash and silica fume increase compressive strength up to 15% and 20% respectively. For further improvement in compressive strength 20% y ash and 10% silica fume are added in percentage of cement. Because addition in cementitious content improves the cement paste bond which improves compressive strength. Fly ash and silica fume increase compressive strength up to 15% and 20% respectively. Fly ash and silica fume also improves the exural and split tensile strength of pervious concrete. Max- imum exural strength is 3.93 MPa for silica fume mix. And maximum split tensile strength is 1.89 MPa for silica fume mix. Chapter 1 includes introduction of pervious concrete, objective and scope of the investigation. Chapter 2 includes a literature survey for pervious concrete. Chapter 3 provides experimental details of investigation. Chapter 4 shows the results of ex- perimental investigation and their discussion. And chapter 5 provides conclusion of the experimental investigation followed by references.