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Porous surfaces have been used all over the world in source control techniques to minimize flooding problems in car parks. Several studies highlighted the reduction in the infiltration capacity of porous mixture surfaces after several years of use. Therefore, it is necessary to design and develop a new methodology to quantify this reduction and to identify the hypothetical differences in permeability between zones within the same car park bay due to the influence of static loads in the parked vehicles. With this aim, nine different zones were selected in order to check this hypothesis (four points under the wheels of a standard vehicle and five points between wheels). This article presents the infiltration capacity reduction results, using the LCS permeameter, of Polymer-Modified Porous Concrete (9 bays) and Porous Asphalt (9 bays) surfaces in the University of Cantabria Campus parking area (Spain) 5 years after their construction. Statistical analysis methodology was proposed for assessing the results. Significant differences were observed in permeability and reduction in infiltration capacity in the case of porous concrete surfaces, while no differences were found for porous asphalt depending on the measurement zone.

Intense urban growth during the last decades [

Porous surfaces are one of the main Sustainable Urban Drainage Systems (SUDS) for source control in car park areas [

Previous studies, [

A new methodology was created for this research. Firstly, a scheme of field tests was created by using the LCS permeameter to measure the permeability, and finally, a statistical scheme of several analyses was designed and developed specifically for this kind of on-site test.

The aim of the new methodology presented in this paper was twofold. Firstly, the analysis of the influence of the porous mixture surface type on the permeability and the reduction in the infiltration capacity after 5 years of use. Secondly, the analysis of the possible differences in the infiltration capacity in different zones within the pervious parking bays.

The whole study was carried out in the “Las Llamas” parking area in the University of Cantabria campus in Santander (Spain) 5 years after this car park was opened for light traffic. No maintenance operations have been carried out during this period. This parking area registers intense traffic activity every day, being nearly 100% occupied. Eighteen car parking bays of 4.2 m long and 2.4 m wide were analyzed with nine bays of Polymer Modified Porous Concrete (PMPC) and nine of Porous Asphalt (PA) surfaces (

The specific characteristics of the two porous mixture surface materials used can be checked in [

(

The infiltration capacity reduction was analyzed through the permeability results obtained now (after 5 years of operational life) in each test carried out using the LCS permeameter [

Nine different points were selected within each car parking bay in order to undertake the LCS tests. Each point represents a specific zone (

The permeability results in the tests were partially described based on permeability ranges defined by [

Criteria for defining the permeability of a porous mixture surface when using the LCS permeameter.

Time (s) | Permeability (cm/s) | Score |
---|---|---|

<50 | >0.50 | Newly built |

50–100 | 0.25–0.50 | High |

100–200 | 0.13–0.25 | Medium |

>200 | <0.13 | Poor |

To achieve the objectives explained in the introduction, a statistical methodology was designed, as can be seen in

Scheme of the statistical methodology designed.

The statistical approach begins with the analysis of the normality distribution of the data in order to decide the path to follow in the statistical scheme in

The distribution of the permeability values registered using the LCS permeameter at each measurement point of the analyzed parking bays of both types of pervious surfaces is in

It can be observed descriptively that there are differences in the infiltration capacity among the different measurement zones on both types of pervious surfaces, generally showing a reduction in infiltration capacity in some wheel-surface contact zones. Considering the average permeability values in each measurement zone of each pervious surface type, the average reductions of the infiltration capacity were calculated and the results are shown in

Box-plots of the average values of permeability in each measurement zone of parking bays.

Average permeability and reduction of the infiltration capacity values registered in each measurement zone within each Polymer Modified Porous Concrete (PMPC) surface car park and their corresponding score.

Measurement zone | Permeability (cm/s) | Score | Reduction of the infiltration capacity (%) |
---|---|---|---|

1 | 0.41 | High | 79..65 |

2 | 0.69 | Newly built | 65.62 |

3 | 0.47 | High | 76.45 |

4 | 0.31 | High | 84.47 |

5 | 0.54 | Newly built | 73.22 |

6 | 0.25 | High | 87.62 |

7 | 0.39 | High | 80.67 |

8 | 0.40 | High | 79.97 |

9 | 0.26 | High | 87.24 |

Mean value | 0.41 | High | 79.43 |

Although the average value of the PMPC surface infiltration capacity demonstrated a high decrease of 79.43% (

As can be seen in the box-plots in

Average permeability and reduction of the infiltration capacity values registered in each measurement zone within each Porous Asphalt (PA) surface car park and their corresponding score.

Measurement zone | Permeability (cm/s) | Score | Reduction of the infiltration capacity (%) |
---|---|---|---|

1 | 0.20 | Medium | 83.52 |

2 | 0.27 | High | 77.46 |

3 | 0.21 | Medium | 82.40 |

4 | 0.22 | Medium | 81.70 |

5 | 0.30 | High | 74.85 |

6 | 0.21 | Medium | 82.57 |

7 | 0.17 | Medium | 85.61 |

8 | 0.18 | Medium | 85.05 |

9 | 0.18 | Medium | 85.23 |

Mean value | 0.22 | Medium | 82.04 |

Box-plots of the average values of permeability (

The first step was to check the normality of both outcome variables by using the Kolmogorov-Smirnov test. Neither variable had a normal distribution. Therefore, non-parametric significance analyses were carried out (

Significance tests shown in

Mann-Whitney and Kruskal Wallis significance tests for the outcome variables.

Significance test | Parameter | Permeability | Reduction of the infiltration capacity |
---|---|---|---|

Mann-Whitney * | U de Mann-Whitney | 1888.5 | 2716.5 |

Asymptotic significance | 0.000 | 0.058 | |

Kruskal Wallis ** | Square Chi | 12.493 | 13.329 |

Asymptotic significance (bilateral) | 0.131 | 0.101 |

Notes: * Grouping variable: type of porous mixture surface; ** Grouping variable: measurement zone.

Once the influence of the porous mixture surfaces has been demonstrated in

Significance analyses for k-independent samples (measurement zones) by using Kruskal Wallis test.

Type of surface | Statistical Significance Test | Permeability | Reduction of the infiltration capacity |
---|---|---|---|

PMPC | Square ChiChi | 17.752 | 17.742 |

Significance (bilateral) | 0.023 | 0.023 | |

PA | Square Chi | 4.397 | 4.522 |

Significance (bilateral) | 0.820 | 0.807 |

Note: Grouping variable: measurement zone.

The results shown in

Therefore, both the statistical methodology and the measurement zones shown in this article can be used for present and future research when using the LCS permeameter to study the infiltration behavior of porous mixture surfaces on-site during their operational life.

The statistical methodology described in this article has proven its efficiency in this particular scenario. Therefore, this methodology could be used in similar investigation in order to prove the general suitability of materials used in infiltration surfaces

In this field study, permeability is significantly different for PMPC and PA surfaces after 5 years of use, as it was at the beginning of their operational life, the PMPC surfaces having higher permeability values.

No significant differences were found between PMPC and PA surfaces regarding their infiltration capacity reduction after 5 years of use.

The measurement zones proposed for this research for analyzing the infiltration capacity behavior of a porous surface car parking bay after 5 years have demonstrated a significance influence of the zone on permeability results for PMPC surfaces.

No significant differences were identified among all the measurement zones for PA surfaces, its infiltration behavior being quite uniform after 5 years of use.

This study was funded by the Spanish Ministry of Economy and Competitiveness through the research projects BIA2009-08272 and BIA2012-32463 with funds from the State General Budget (PGE) and the European Regional Development Fund (FEDER). The authors wish to thank the Santander Roads Group (GCS) and Construction Technology Research Group (GITECO) of the University of Cantabria, the Sustainable Drainage Applied Research Group of the Coventry University, and the companies SIEC S.A., Hanson-Formpave, Bloques Montserrat S.L. and DANOSA for their collaboration. Luis A. Sañudo-Fontaneda would also like to thank the Ministry of Economy and Competitiveness for the Researcher Formation Fellowship (FPI) funding for his research activity in the University of Cantabria.

The four co-authors designed the research methodology, specifically Luis A. Sañudo-Fontaneda and Valerio C.A. Andrés-Valeri carried out the test in the car park and the statistical analysis of the results, while Jorge Rodriguez-Hernandez and Daniel Castro-Fresno validated the analysis, lead the discussion and stated the final conclusions.

The authors declare no conflict of interest.