Mechanical and Microscopic Characteristics of Polyurethane-Based Pervious Pavement Composites

Conventional pervious pavement materials (PPM) that consist of cement and aggregate materials are known for poor durability due to their brittle behavior. Thus, to enhance the durability, we fabricated polymeric PPMs from durable and abundant polyurethane (PU) and undertook mechanical and microscopic characterizations. PU-based PPM samples with varying aggregate sizes were produced and examined to test their compressive strength and water permeability. Furthermore, X-ray micro-computed tomography (micro-CT) was implemented to analyze the samples’ pore and tortuosity characteristics. Through the micro-CT analysis, the morphological characteristics of PPM’s internal structures were identified and quantitively analyzed the correlations between the pore size distribution, connectivity, and tortuosity within the samples. Finally, the microstructures derived from micro-CT were generated as a finite element model and also numerically determined the stress distribution generated inside.

Mechanical and Microscopic Characteristics of Polyurethane-Based Pervious Pavement Composites

Conventional pervious pavement materials (PPM) consist of cement and aggregate materials and are known for poor durability due to their brittle behavior. Herein, we fabricated polymeric PPMs from durable and abundant polyurethane (PU) to enhance the durability of the material and undertook mechanical and microscopic characterizations. PU-based PPM samples with varying aggregate sizes were produced and the compressive strength and water permeability of each were examined. The pore and tortuosity characteristics of the specimens were analyzed using X-ray micro-computed tomography (micro-CT). Through the micro-CT analysis, the morphological characteristics of the internal structures of PPM were identified and the correlations between the pore size distribution, connectivity, and tortuosity within the specimen were quantitatively analyzed. The microstructures derived from micro-CT were generated as a finite element model and the stress distribution generated inside was numerically determined.

Water Retention Performance at Low-Impact Development (LID) Field Sites in Taipei, Taiwan

Low-impact development (LID) aims to retain stormwater at source sites rather than achieve water drainage. The infiltration and storage of rainwater on site is the most commonly applied LID design concept, turning impervious pavements into pervious pavements. In this study, three field sites in Taipei city, Taiwan, were monitored. Two of the sites were located on campuses, and one site was a roadside location. They were constructed at different times and had distinct purposes, but the common design aspect was the infiltration function of the ground surface. We monitored the water retention performance at the above three sites and applied a verified stormwater management model (SWMM) to characterize the performance at these case sites. The observed data show that if the accumulative rainfall was lower than 20 mm, the water retention rate at each of the three case sites reached almost 50%; at 60 mm rainfall, the rate was 40%. With increased rainfall amount, the water retention rate decreased because the storage capacity was limited. Because water retention is typically controlled by the infiltration capacity, the rainfall intensity dominated the performance. At the three field sites, the water retention rate was 40% on average at a rainfall intensity below 20 mm/h. Above this rainfall intensity, the infiltration performance of the pervious pavement decreased. The verified model was applied to assess the performance at the three sites under the Taipei city drainage system design standard, i.e., the five-year recurrent period storm level, at 78.8 mm/h. The results demonstrate that the water retention rates were 9.1%, 14.2%, and 61.0% at the three sites, indicating that the pervious pavement could reduce the loading of the current stormwater drainage system. Dispersed sites should be considered in urban stormwater management to mitigate flooding risk in urban areas.

Pervious Pavement Blocks Made from Recycled Polyethylene Terephthalate (PET): Fabrication and Engineering Properties

The importance of permeable and pervious pavements in reducing urban stormwater runoff and improving water quality is growing. Here, a new pervious pavement block material based on recycled polyethylene terephthalate (PET) waste is introduced, which could contribute to reducing global plastic waste via PET’s utilization for construction material fabrication. The engineering properties and durability of recycled PET aggregate (RPA) pervious blocks are verified through flexural tests, in situ permeability tests, clogging tests, and freeze-thaw durability tests, and their cost-effectiveness is assessed by comparison with existing permeable/pervious pavers. Their engineering and economic characteristics confirm that the RPA pervious blocks are suitable for use in urban paving.