Use of Polyurethane Foam in Pervious Concrete

Abstract

In recent times, paver blocks made of pervious concrete are being replaced with the concrete paver blocks because of its nature of ground water recharge. It presents a severe long-term problem of flooding in areas with heavy rainfall. Cement, water, coarse aggregate (mainly grit), and a small amount of fine aggregates are used to create Pervious Concrete, a type of concrete with a higher void ratio. Sometimes, fine aggregates can be completely neglected. A porous medium is created by pervious concrete, enabling water to reach the soil beneath.

Use of pervious concrete paver blocks are very useful in avoiding water clogging problems and beneficiary ground water recharge but in the voids of pervious concrete, there are chances of clogging because of finer (than voids) sand particles or other finer solid particles which won’t let pass water to the ground freely. To avoid this problem, pieces of PUR foam can be incorporated in the pervious concrete paver blocks where the foam particles will set in the voids of paver blocks and it will also let water pass through them. The properties like pH, DO, TDS and electrical conductivity of the water passing through PUR foam were determined and it was concluded that it will have no impurities.

In order to get the properties of pervious concrete such as density, void ratio and compressive strength, several trials were performed. For preparing pervious concrete, several mix proportions were taken into count where cement content was 375 kg/m3. Proportion of coarse aggregate with respect to cement was taken 1:4 and 1:3 in several trials. As for the type of coarse aggregates, all 3 possible variations were done i.e., 100% grit, 100% kapchi, combination of 60% kapchi and 40% grit. Water-cement ratio was also taken as 0.4 initially and after several observations it was reduced to 0.35. Cementitious materials like fly ash and silica fume were also used as several percentage of replacement of cement where replacement of cement with silica fume gave better properties of pervious concrete. From the optimum mix having cement content of 375 kg/m3, C:A is 1:3 and having water-cement ratio of 0.4 Pervious Concrete Paver Blocks were prepared and tested their physical properties like compression strength, abrasion resistance, flexural strength and split tensile strength as per standards.

To determine the variation in properties of pervious concrete after incorporating PUR foam, all the various types of foam were incorporated in pervious concrete about 0.1% of coarse aggregates. The particular foam (having minimum density) containing mix giving best results, is to be further incorporated in pervious concrete paver blocks. After comparing properties of pervious concrete paver blocks with and without PUR foam it was found out that there is slight decrement in compressive strength and abrasion resistance of pervious concrete incorporated with PUR foam than normal pervious concrete. All other properties like density, void ratio, flexural strength and split tensile strength were not that affected by incorporation of PUR foam.

The upper surface of pervious concrete paver blocks with and without PUR foam were analysed using image analysis technique where the number of voids and void ratio of surface can be found out from the high resolution picture of the surface of specimen.

Further a stretch of paver blocks incorporated with PUR foam having dimensions of 48 cm × 62 cm having only bedding layer of coarse sand was prepared which resulted into leakage of water from below surface of boundaries. Hence another stretch having dimensions of 80 cm × 80 cm with proper percolation system was prepared and it found out that a proper percolation system is to be adapted in order to utilize the paver blocks properly.