Porous Concrete

To make high strength normal concrete we use coarse aggregates; fine aggregates; cement and water. But for making concrete porous it is advisable to use minimum fine aggregate content or even avoid its use because they are used as void filling materials and they make concrete denser and compact, but in porous concrete we need interconnecting voids for water to percolate through it easily. This paper aims at experimentally studying the effect of maximum nominal size of aggregate on the properties of porous concrete and subsequent change in its strength. Concrete test specimens are prepared for different gradation and test for permeability, compressive strength, density, tensile and flexural strength, and workability is carried out on these blocks. Various properties of fresh and hardened concrete is recorded and studied with the help of graphs. The strength of porous concrete is lower than the normal conventional concrete and as the porosity characteristic is enhanced its strength is reduced and this behavior is showed with the help of graphs. Keywords: Porous concrete as road pavement, density, workability, compressive, water permeability test and tensile/flexural strength, maximum nominal size of aggregate. I. INTRODUCTION Porous concrete are being used in many parts of the world as a green solution to overcome various environmental problems like decreasing ground water level and subsequent flooding due to lack of absorbing surface in the city. These porous concrete pavements can be useful in managing quality and quantity of urban storm water. Ordinary concrete pavement consists mainly of conventional cementitious materials (organic inorganic and organic-inorganic combination), granular aggregate, water, chemical admixtures and mineral admixtures. This type of concretes are impervious and surface flow is hard to penetrate, causing flooding in cities, moreover the air permeability of normal concrete is poor, which is not convenient for heat exchange. When sun irradiates the ground, the temperature of the earth increases, this will lead to urban heat island effect and urban environment deterioration. As compared to conventional concrete the porous concrete reduces or avoids the use of fine aggregates which forms interconnecting voids or porous microstructure. The intercommunicating pores in theses porous concrete makes the pavements have good permeable performance. And these would guide to the promotion of sponge city in future. Experiments and researches on porous concrete as pavement materials is essential in order to use it more frequently in place of conventional pavement materials to reduce the bad environmental effects caused by normal pavements like drainage problems, ground water depletion and flood problems during excessive rain in urban areas where larger area of roads and pavements are covered with impervious non absorbing conventional pavements. Pavements made with impervious conventional concrete offers greater strength and durability as they are compact in structure with void filling fine aggregates and are more resistant to wear, tear and impact loadings but they are incapable of providing proper drainage of water through them and thus don't help in flood problem in urban area caused due to excessive rain and poor drainage and don't help in reducing the load of water treatment plants Though the strength of permeable concrete pavements is not as high as conventional concretes initially this porous concrete pavements were being used only for light traffic of foot and for house yard surfacing but with experiments on porous concrete and wide awareness about its advantages over conventional concrete on environment its use is made possible for further using it as traffic pavement materials and further experiments are going on to increase its strength. The advantages of this type of porous concrete are lower density, lower cost due to lower cement content and very low or no sand content, lower thermal conductivity (intrinsic gaps in these concrete provide reduced thermal conductivity as compared to the dense conventional concrete.) relatively low drying shrinkage, less or no capillary movement of water, better insulating characteristics than conventional concrete because of the presence of large voids according to Fulton's concrete technology (1994) and Neville (1981).

Portland cement pervious concrete (PCPC) is increasingly being used in the United States in sidewalks and parking lots due to its benefits in reducing the amount of runoff water and improving water quality. In the United States, PCPC typically has high porosity and low strength, which has resulted in limited use of pervious concrete in hard wet freeze environments (i.e.,

In this study, the relationship between porosity and compressive strength for porous concrete (PC) was
investigated. The effect of mixture design parameters particularly, water-to-cement ratio (W/C) and size of aggregate on
the porosity and compressive strength of PC was evaluated. To investigate the role of W/C and aggregate size on this
testing procedure, the experiments were performed on specimens of two aggregates size and four range of W/C. The
PC mixtures were made with W/C in the range of 0.28-0.34, 350kg/m3 cement content and 19.5mm and 9.5 maximum
size of aggregate. PC mixes were made from each aggregate and were tested. The results showed that the W/C and
aggregate size are key parameters which significantly affect the porosity of PC. Investigation of compressive strength
and porosity for the various mix designs showed a clear dependence on these parameters. The measured values fall
within the expected range obtained from a review of the literature. Compressive strength of coarse porous concrete
(CPC) is smaller than compressive strength of fine porous concrete (FPC) and the porosity of CPC are bigger than
porosity of FPC. In general, increased W/C yields a smaller porosity and higher compressive strength. This approach
can reduce the number of trial batches needs for target performance of PC samples

Porous concrete or pervious concrete consists of no-fines, open-graded Portland concrete mixture usually with 15–25% voids, which enables water to be drained quickly. In the literature, porous concrete is cited as a material typically used in low-traffic areas such as residential streets, parking lots, sidewalks, recreation trails, plazas, and other paved areas. However, it has been reported that a porous concrete layer over a conventional concrete base is an efficient means of reducing tyre spray and hydroplaning. The desirable properties are: significant noise reduction and drainage; acceptable strength and stiffness; adequate surface properties with respect to traffic safety such as skid resistance and sufficient service life; bonding with underlying dense concrete; and costs comparable to those of conventional pavements. Porous concrete had been reportedly used on airport runways. The aim of this study was to verify the drainage properties of porous concrete for reducing hydropl...