The use of Pervious Concrete (PC) increased in the last years as an alternative to solve the run-off problem. PC shows a high percentage of empty spaces/gaps, which vary from 10 to 35%, facilitating the flow of rain and water through its structure. PC presents higher k permeability coefficient compared to conventional concrete. Permeability is the main property of PC, although there is no standardized method that guarantees the correct and precise measurement of such property in laboratory conditions. Currently, two main methodologies are used to assess the permeability coefficient: the falling head and the constant head permeability tests. In that regard, the American Concrete Institute recommends the use of the first method, although no comparison was done between them. Furthermore, the recommendations do not consider the use of sustainable aggregates during the production of the PC. In this study, the permeability tests were explained and used to assess the permeability coefficient of different mixes of PC produced with sustainable aggregates. The experimental results were used to analyze the relationship between the porosity and the permeability of concrete and compare the performance of the falling head and constant head permeability tests. The study presents the advantages of performing the constant head permeability test to assess the permeability of the PC

The aim of this study was to propose a correlation for the hydraulic parameters of pervious concrete (PC). Thus, three aggregates from civil construction waste and one basalt aggregate (reference) were used to produce PC. The ratio c/a (cement: aggregate) 1:3.26 and a w/c ratio of 0.34 were used in all mixtures. Compressive and flexure tensile strength tests were performed to mechanically characterize the mixtures produced, whereas porosity and constant head permeability tests were also carried out to assess the material hydraulic properties.Firstly, the experimental results were compared with the requirements established in international guidelines (ACI 522R-10, NBR 16416(2015) and VTT-R-080225-13). The results complied with the guidelines indicating it is feasible to produce pervious concretes with the sustainable aggregates used in the study in low structural applications such as walkways. On the other hand, a correlation between permeability and porosity was proposed based on Darcy’s and Bernoulli’s laws. The proposed equation, obtained by means of a non-linear regression, is an exponential equation that characterizes the hydraulic efficiency of the internal channels of the material considering the pores interconnection. The correlation between porosity and permeability was finally validated using results from the literature showing the same trend found in laboratory, and therefore it was demonstrated that the proposed correlation in an efficient tool to predict the hydraulic efficiency of pervious concrete.

This study aims to evaluate the influence of B. subtilis AP91 spores addition on the mechanical properties of mortars. B. subtilis strain AP91, isolated from rice leaves of the needle variety, which has an early cycle of production, was used at the concentration of 105 spores/mL in mortars with cement-to-sand ratio of 1:3 (by weight) and water-to-cement ratio (w/c) of 0.63. These spores were added in two different ways: in the mixing water and by immersion in a solution containing bacterial spores. Scanning Electron Microscope (SEM) analysis showed crystals with calcium peaks on the EDS, which possibly indicates the presence of bioprecipitated calcium carbonate. The results obtained in the mechanical analysis showed that the bioprecipitation of CaCO₃ by B. subtilis strain AP91 was satisfactory, particularly when the spores were added in the mixing water, increasing the compressive strength up to 31%. Thus, it was concluded that the addition of B. subtilis AP91 spores in the mixing water of cement mortars induced biocementation, which increased the compressive strength. This bioprecipitation of calcium carbonate may very well have other advantageous consequences, such as the closure of pores and cracks in cementitious materials that could improve durability properties, although more research is still needed on this matter.