ASU Electronic Theses and Dissertations

In recent years, an increase of environmental temperature in urban areas has raised many concerns. These areas are subjected to higher temperature compared to the rural surrounding areas. Modification of land surface and the use of materials such as concrete and/or asphalt are the main factors influencing the surface energy balance and therefore the environmental temperature in the urban areas. Engineered materials have relatively higher solar energy absorption and tend to trap a relatively higher incoming solar radiation. They also possess a higher heat storage capacity that allows them to retain heat during the day and then slowly release it back into the atmosphere as the sun goes down. This phenomenon is known as the Urban Heat Island (UHI) effect and causes an increase in the urban air temperature. Many researchers believe that albedo is the key pavement affecting the urban heat island. However, this research has shown that the problem is more complex and that solar reflectivity may not be the only important factor to evaluate the ability of a pavement to mitigate UHI. The main objective of this study was to analyze and research the influence of pavement materials on the near surface air temperature. In order to accomplish this effort, test sections consisting of Hot Mix Asphalt (HMA), Porous Hot Mix asphalt (PHMA), Portland Cement Concrete (PCC), Pervious Portland Cement Concrete (PPCC), artificial turf, and landscape gravels were constructed in the Phoenix, Arizona area. Air temperature, albedo, wind speed, solar radiation, and wind direction were recorded, analyzed and compared above each pavement material type. The results showed that there was no significant difference in the air temperature at 3-feet and above, regardless of the type of the pavement. Near surface pavement temperatures were also measured and modeled. The results indicated that for the UHI analysis, it is important to consider the interaction between pavement structure, material properties, and environmental factors. Overall, this study demonstrated the complexity of evaluating pavement structures for UHI mitigation; it provided great insight on the effects of material types and properties on surface temperatures and near surface air temperature.

The built environment is responsible for a significant portion of global waste generation.

Construction and demolition (C&D) waste requires significant landfill areas and costs

billions of dollars. New business models that reduce this waste may prove to be financially

beneficial and generally more sustainable. One such model is referred to as the “Circular

Economy” (CE), which promotes the efficient use of materials to minimize waste

generation and raw material consumption. CE is achieved by maximizing the life of

materials and components and by reclaiming the typically wasted value at the end of their

life. This thesis identifies the potential opportunities for using CE in the built environment.

It first calculates the magnitude of C&D waste and its main streams, highlights the top

C&D materials based on weight and value using data from various regions, identifies the

top C&D materials’ current recycling and reuse rates, and finally estimates a potential

financial benefit of $3.7 billion from redirecting C&D waste using the CE concept in the

United States.

Chloride solutions have historically been used to stabilize roads and to prevent dust; however, very little work has been done on investigating the soil stabilizing benefits from interactions between salt solutions and different soil types. The primary goal of this research was to analyze the feasibility of utilizing a salt waste product as an economically and environmentally responsible means of dust control and/or soil stabilization. Specifically, this study documents an investigation leading to the understanding of how the addition of saline based waste products, when using a soil stabilizer, modifies the strength behavior of soils.

The scope of work included the evaluation of current literature, examination of the main challenges meeting relevant governmental regulations, and exploring the possibility of using saline waste to improve roadways.

Three soils were selected, treated with varying amounts of salt (calcium chloride, CaCl2), and tests included soil composition and classification, correlation of soil characteristics and salt, and obtaining strength parameters that are typically used in pavement design and analysis. The work effort also included the determination of the optimum dosage of salt concentration for each soil. Because Lime treatment is also commonly used in soil stabilization, one of the soils in this study included a treatment with Lime for comparison purposes.

Results revealed that when salt concentration was increased, a decrease in the plasticity index was observed in all soils. A modest to considerable strength gain of the treated material was also observed for two of the soils; however, a strength loss was observed for the third soil, which was attributed to its low clay content.

When comparing the soil corrosive potential, the additional salt treatment showed promise for increasing strength, to an extent; however, it changes the chemical properties of the soil. The soils prior to treatment were corrosive, which could be managed with appropriate techniques, but the salt increases the values to levels that could be potentially cost prohibitive if salt was used by itself to treat the soil.

The pavement design and performance investigation revealed that the Vineyard soil treated at 16% CaCl2 had an improvement that is comparable to the Lime treatment. On the other hand, the Eager soil showed very little pavement performance improvement at 8% CaCl2; this goes back to the effect of acid on the clay mineralogy. It was also postulated that using salt by-products to stabilize highway shoulders could be beneficial and save a lot of maintenance money when it comes to cleaning unwanted vegetation. A salt saturated soil structure could help in dust control as well.

Future environmental challenges for salt leaching that could affect agriculture in developing countries will still need to be carefully considered. The chlorine levels in the soil would increase, and if not treated, can potentially have corrosive effects on buried structures. Future research is recommended in this area and to also evaluate soil stabilizing properties of varying proportions of Lime and salt using the approach provided in this study.