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Investigation into the fracturing of asphalt pavement surfaces using daikon radishes
Date
2025
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
The United States consistently ranks among the top three countries worldwide in the use of paving material. Paved surfaces—such as those used in residential areas, parking lots, and roads—are essential in urban planning and infrastructure development. However, some of these paved surfaces are abandoned and no longer in active use. The use of mechanized equipment in removing such pavement is limited especially due to the small-scale nature of the abandoned pavement, sensitivity of location, noise and air pollution ordinances, or environmental concerns. Abandoned asphalt pavements are not inert; they can pose several significant environmental risks such as the urban heat island effect, increased runoff due to reduced water infiltration rate, loss of ecosystem services, and abrupt temperature fluctuations in the local water system. It is important to develop strategies to address these concerns posed by paved surfaces. ☐ This study investigated the use of daikon radishes (Raphanus sativus var. longipinnatus, Tillage and Alpine cultivars) to fracture an aged asphalt pavement surface. Field data was collected from a study site located within Winterthur Museum, Gardens, and Library in Delaware, USA. Between 2021 and 2025, eight seasons of semi-annual daikon radish planting and cultivation were conducted at this study site. The research involved archival image analysis, field observations, laboratory testing, and controlled experimental setups to evaluate the structural impact, mechanical properties, and environmental impact of growing radishes to fracture pavement surfaces. ☐ First, asphalt pavement material properties from the study site were characterized using standard specification tests. Archives of high-resolution overhead photographs of the study site before planting and after harvesting for every planting season were used to map pavement distresses in the study site using AutoCAD®. To access the study site hydrological conditions, water infiltration rates on different pavement conditions were measured using the Double-Ring Infiltrometer at the end of the eighth planting season. ☐ Spring-loaded prototypes were designed to monitor the radish root's growth behavior in controlled confinement, independent of external climatic conditions like temperature and precipitation. Finally, a life cycle inventory of carbon dioxide equivalent emissions from one year of radish growth at the study site was completed. ☐ The study site demonstrated the potential of daikon radish growth as a viable technique for disintegrating aged pavement. Comparing values before radish planting in May 2021 and at the end of the eighth radish planting season in February 2025, the total crack length and area of de-pavement increased by ~34% and ~930%, respectively. A new crack pattern connecting one or more radish planting holes emerged at the site; 74% of new cracks at the study site are along these holes. Water infiltration tests showed that these cracks caused by growing radishes allow for more water infiltration than alligator cracking caused by general wear-and-tear at the study site. Results show that full de-pavement of the site is not necessary to achieve an increase in the water infiltration rate. ☐ Radish growth in a controlled environment inside spring-loaded prototypes demonstrated that radish roots can exert measurable pressure against confining surfaces and adapt their growth behavior to overcome external constraints. The maximum confinement pressure measured in this study was 12 psi for an Alpine radish. Shapes of the radishes after harvest showed that the Alpine radish develops a larger diameter at points where it felt a greater resistance from the spring. The emissions associated with radish cultivation at the study site (without considering its carbon sequestration ability) range from 9.73 to 9.99 kg CO₂ equivalent per yearly planting of daikon radish. This is roughly equivalent to tailpipe CO2 emissions from burning one gallon of fuel. The major contributors to these emissions are the water supply system and fertilizer use. Per this metric, the environmental impact of growing radishes at the study site is low. ☐ This investigation shows that daikon radish roots can apply and sustain pressure to create weak points and exploit pre-existing cracks, initiate and propagate new cracks, and weaken the surfaces of aged asphalt pavements. Over time, environmental factors such as moisture infiltration, freeze-thaw cycles, and biological decay could amplify the effects of root growth. With this, the water infiltration rate of a paved site can be significantly improved compared with its current condition. By integrating agricultural and engineering principles, the use of radishes in pavement fracturing presents an innovative and environmentally friendly alternative to conventional mechanical methods for removing aged pavement.
Description
Keywords
Asphalt, Cracks, Environment, Fracturing, Growth pressure, Radish