Research of The Effect of Using Waste/recycled Materials for Insulation

Pavements in cold regions are prone to frost damages during winter as a result of prolong sever below zero temperature. Frost heave can negatively affect the performance and ride quality of the road. At the end of the frost season, when thawing begins in the sublayers, pore water pressure builds up in the subgrade soil. This reduces the resilient modulus of the subgrade considerably and degrades the structural integrity of the pavement. Reducing the depth of frost penetration into the pavement structure can enable design engineers to decrease the thickness of the base/subbase layers; hence, reduce the use of natural aggregate and advance towards a more economical and sustainable design. Insulating the pavement foundation is one strategy to reduce heat loss from the pavement structure and maintain pavement subgrade temperatures above freezing during the winter months. While the number of test roads that are designed and constructed for in-situ measurement and evaluation of pavement performance are limited, there is a lack of knowledge on the effect of using new and recycled material on pavement. This research is designed to conduct a state-of-the-art investigation on the effect of using waste/recycled materials for insulation.

As part of the research, controlled tests were performed at the University of Alberta’s Integrated Road Research Facility (IRRF), a full-scale test road, located in Edmonton, Alberta, Canada. The IRRF test road has three monitoring sections with insulation made of bottom ash (100 cm) and two different thicknesses of polystyrene boards (5 cm and 10 cm), and a control section (CS) with no insulation. The sections are fully instrumented across the depths of the pavement using environmental probes. Based on the results from field monitoring and using the Principal of Conservation of Energy, the effects of using insulation layers on the thermal regime of the pavement are investigated and the effectiveness of each insulation layer is quantified. The thermal and moisture regime of the pavement structure over time are used to divide a year into freezing, thawing and non-freeze- thaw periods. The thermal and moisture variation in different seasons can affect the loading characteristics of the pavement layers over time.

In an attempt to quantify the impact of seasonal changes (fluctuation of different layers modulus) on the overall strength of the pavement, Falling Weight Deflectometer (FWD) tests were carried out on the IRRF test road and the results are comparing with the temperature and moisture regime in the pavement. The time history data collected from field FWD tests is used to identify the characteristic response of different sections. The structural behavior of each section is evaluated and the long term performance of each section is quantified in terms of fatigue cracking occurrence on the pavement using the elasto-plastic and stress-strain theories.

To investigate the cost effectiveness of using insulation materials, the capital construction cost of the insulated roads, along with substituting the subgrade material with high quality granular base course (GBC) material is calculated. Recommendations are provided for optimum thickness of insulation material based on the distance and frost depth of the road from the location of the insulation material sources An essential part of this research is the creation of a finite element model for a better prediction of temperature changes in the insulated pavement system. The model has been calibrated using field data collected in this research. In order to develop a predictive model, it is necessary to incorporate laboratory test results on material characteristics in different well-controlled environmental conditions. The model is constructed in the Geo-Studio software.

Based on this research, it can be concluded that, Bottom Ash as a waste material can be used as an insulation layer in road construction. Bottom Ah, can effectively decease the frost penetration, while it provides a favorable load bearing capacity and pavement performance during the critical thaw weakening season.