Contribution of Porous Concrete to Control Flooding and Urban Drainage Systems (PAP014912)
Paulo Cezar Dias de Alencar, Oscar de Moraes Cordeiro Netto
The scenario of climate changes and urban development have caused changes on the runoff, being necessary to implement actions in order to restore the initial conditions, or at least, mitigate the impacts. To solve this question, were developed sustainable urban drainage techniques that adopt delaying runoff, favoring evaporation or infiltration. Among these, the pavement of porous concrete has been studied and applied in different situations. This paper aims to present an assessment of the direct relationship between the voids of a porous concrete and characteristic compression resistance (fck), relating them to the draining capacity. For that, it was built in Brasilia, DF, an experimental area of 37.5 m² aimed at three parking spaces in a suitable place to clogging of the porous concrete location. Each place of 12.5 m² was built with 15 cm thick of concrete on a draining bed of 30 cm thick, adopting different techniques for paving each parking place. The evaluation of the hydraulic performance occurred through runoff generated by artificially simulated rain. The rain simulations were first performed with the new pavement, when it was found superior absorbency to simulated rainfall of 2.35mm/min. The experimental rain simulation apparatus was then demobilized and the parking area released for a regular vehicle use. At the end of the rain season in Brasilia, the rain simulator was installed again for other experiments when it was found total clogging of the pavement. Subsequently it was proceeded the floor cleaning and the final measurements of the permeability of the pavement, in that time, the maximum infiltration rate observed was 1.75 mm/min. After the simulated rains, the extraction of 30 testimonies of the pavement was performed. Divided into two groups, half of them followed for determining the void content, while others, for determining the fck. The next step of the work dealt to correlate these properties. At that time, it was determined that in places where the consolidation of fresh concrete was held void ratio was 15.4% and fck 26.3MPa. Whereas, where the porous concrete was simply spread and smoothed, were obtained 19.2 % of voids, and fck 20.3 MPa. It was also shown that the recovery of permeability failed to complete success, since for a rain of 29.4L/min was obtained maximum infiltration of 13.9L/min for the pavement with less voids, while for other places, were achieved 21.9L/min. This result showed that smaller voids represent a greater resistance to cleaning, and, for that reason, in this pavement, a reduction of drainage capacity occurred. The experiment also established that the greater compactness provided by the application of compression during the execution of porous concrete gives greater compactness to the plate, providing greater resistance to compression and enabling higher withstand loads, moreover, there was less draining capacity of the floor. Another consequence of the greater compactness was the greatest exposure to pavement clogging, which may shorten the lifetime of the pavement.