The sources of natural or virgin coarse aggregates are diminishing in alarming rate and its production is quite expensive, uses a lot of energy, and is not environmental friendly. Hence, utilizing the recycled aggregates like reclaimed or recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP) on road pavement will not only preserve the natural aggregates but also reduce the negative environmental impact. It also helps to conserve the waste landfill sites. The major downside for the use of the recycled aggregate is the quality control during its production. This research characterizes RCA samples obtained from a demolished old foundation and RAP samples from old parking lot and determines their suitability as road pavement materials. Virgin aggregates, recycled aggregates, and several blended mixtures with 20 to 80% replacement of natural coarse aggregate or virgin aggregate (NCA or VA) by weight with RCA and RAP were prepared and tested for resilient modulus (Mr) and California Bearing Ratio (CBR) test. The durability of the virgin aggregate and recycled aggregate were also determined by micro-deval test. The resilient modulus value of 100% RCA and 100% VA was found to be very similar or higher but for 100% RAP the resilient modulus is higher than that of the 100%VA. The Resilient modulus of the RAP blended mixtures increases with the increase in the content of RAP percentage and for the RCA it was not consistent. The CBR values for the blended mixtures decreases with the increase in the percentage of the recycled aggregates. The micro-deval degradation test result for RCA was more than of VA due to presence adhere materials in RCA.

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Resilient moduli of different surface mixes placed at the Virginia Smart Road were determined. Testing was performed on Field cores (F/F) and laboratory-compacted plant mixed (F/L), laboratory mixed and compacted per field design (L/L), and laboratory designed, mixed, and compacted (D/L) specimens. The applied load was chosen to induce a strain ranging between 150 and 500 microstrains. Two sizes of laboratory compacted specimens (100-mm in diameter and 62.5-mm-thick and 150-mm in diameter and 76.5-mm-thick) were tested to investigate the effect of specimen size on the resilient modulus. At 5°C, the measured resilient moduli for both specimen sizes were similar. However, the specimen size has an effect on the measured resilient modulus at 25 and 40°C, with larger specimens having lower resilient modulus. At 5°C, HMA behaves as an elastic material; correcting for the specimen size using Roque and Buttlar's correction factors is applicable. However, at higher temperatures, HMA behavior becomes relatively more viscous. Hence, erroneous resilient modulus values could result when elastic analysis is used. In addition, due to difference in relative thickness between the 100- and 150-mm diameter specimens, the viscous flow at high temperature may be different. In general, both specimen sizes showed the same variation in measurements. Resilient modulus results obtained from F/L specimens were consistently higher than those obtained from F/F specimens. This could be due to the difference in the volumetric properties of both mixes; where F/F specimens had greater air voids content than F/L specimens. A compaction shift factor of 1.45 to 1.50 between the F/F and F/L specimens was introduced. The load was found to have no effect on resilient modulus under the conditions investigated. However, the resilient modulus was affected by the load pulse duration. The testing was performed at a 0.1s and 0.03s load pulses. The resilient modulus increased with the decrease of the load pulse duration at temperatures of 25°C and 40°C, while it increased at 5°C. This could be due to the difference in specimen conditioning performed at the two different load pulses. Finally, a model to predict HMA resilient modulus from HMA volumetric properties was developed. The model was tested for its fitting as well as predicting capabilities. The average variability between the measured and predicted resilient moduli was comparable to the average variability within the measured resilient moduli. / Master of Science

Resilient modulus is an important property for asphalt concrete design and for mechanistic analysis of pavement response under traffic loading. This study investigates the different factors affecting the resilient modulus of hot mix asphalt. A fractional factorial design of experiment was carried out to investigate six factors each factor was studied at two levels. These factors are: the maximum nominal aggregate size, specimen diameter and thickness, the load pulse form and duration, and the compaction method. Two types of hot mix asphalts with different maximum aggregate sizes (10 mm and 14 mm) were studied. Gyratory and Marshall compaction methods were used to prepare the specimens. Sinusoidal and triangular load pulse forms were used in the measurement of the resilient modulus. This study attempts to examine how the different factors interrelate to affect the resilient modulus. In addition to this, two other investigations will be carried out. The first is the comparison of the strain backcalculated using the resilient modulus test results with the strain measured using strain gages and strain values obtained from finite element modelling (FEM), and determine whether the FEM or the closed form equation is the more accurate method for determining strain. The second is the investigation of the relationship between the flexural, complex and resilient modulus. Analysis of the factorial experimental design showed that the maximum nominal aggregate size is the most important factor affecting the resilient modulus, followed by the load duration, the specimen geometry represented by the thickness and diameter then the interactions between the different factors. The strain comparison suggested that the closed form equations were indeed a suitable approach to determine maximum horizontal strain during a resilient modulus test. The modulus comparison suggested that it is possible to predict either resilient, complex and flexural modulus given that only one of them is known, but only for AC10 specimens.

Typical material used by the Tennessee Department of Transportation for highway bases was evaluated for application to the new Mechanistic-Empirical Pavement Design Guide. Two types of granular Tennessee highway base material were mixed with different stabilizers and tested in the lab according to AASHTO T-307 99 (2003). Unconfined Compressive Strength and California Bearing Ratio tests were also done in an effort to correlate these results with resilient modulus. Three different combinations of base and stabilizer were tested and modeling coefficients were produced. Base structural layer coefficients were generated and compared to coefficients currently in use by TDOT.

Typical material used by the Tennessee Department of Transportation for highway bases was evaluated for application to the new Mechanistic-Empirical Pavement Design Guide. Two types of granular Tennessee highway base material were mixed with different stabilizers and tested in the lab according to AASHTO T-307 99 (2003). Unconfined Compressive Strength and California Bearing Ratio tests were also done in an effort to correlate these results with resilient modulus. Three different combinations of base and stabilizer were tested and modeling coefficients were produced. Base structural layer coefficients were generated and compared to coefficients currently in use by TDOT.

Compacted soils are frequently used as subgrade for pavements as well as commercial and residential buildings. The stiffness and shear strength properties of compacted soils, which are collectively denoted as Ω in this thesis, fluctuate with moisture content changes that result from the influence of environmental factors such as the evaporation and infiltration. For example, mechanistic pavement design methods require the information of resilient modulus (MR), which is the soil stiffness behavior under cyclic traffic loading, and its variation with respect to the soil moisture content determined from laboratory tests or estimation methods. Significant advances have been made during the last five decades to understand and model the variation of the Ω with respect to soil moisture content and soil suction (s) based on the principles of mechanics of unsaturated soils. There are a variety of models presently available in the literature relating the Ω to the s using different approaches. There are however uncertainties extending these models for predicting Ω - s relationships when they are used for a larger soil suction range. In addition, the good performance of these models are only valid for certain soil types for which they were developed and calibrated. Studies presented in this thesis are directed towards developing a unified methodology for modelling the relationship between the Ω and the s using limited while easy-to-obtain information. However, more emphasis has been focused on the MR - s relationships of pavement subgrade soils considering the need for the application of the mechanistic pavement design methods in Canada. The following studies have been conducted: (i) State-of-the-art review on existing equations in the literature for the MR - s relationships is summarized. A comparison study is followed to discuss the strengths and limitations of these equations; (ii) A unified methodology for modelling the Ω - s relationships is proposed. Experimental data on 25 different soils are used to verify the proposed unified methodology. The investigations are applied on small strain shear modulus, elastic modulus, and peak and critical shear strength. Good predictions are achieved for all of the investigated soils; (iii) Performance of the proposed methodology is examined for the MR - s relationships using experimental data of 11 subgrade soils. Reasonably good predictions are achieved for all of the subgrade soils; (iv) Extensive experimental investigations are conducted on the MR - s relationships for several subgrade soils collected from various regions in Canada. Experimental results suggest non-linear variation in the MR with respect to s, moisture content and the external stress. The measured results are modelled using the proposed methodology with adequate success; (v) Additional experimental investigations are performed to determine the variation of the elastic modulus (E) and unconfined compression strength (qu) with the s and the gravimetric moisture content (w) for several Canadian subgrade soils. An approach, which is developed extending the proposed unified methodology, is used to normalize the measured MR - w, E - w and qu - w relationships. It is shown that the normalized MR - w, E - w and qu - w relationships exhibit remarkable similarity and can be well described using the proposed approach. Such similarity in the normalized Ω - moisture content relationships are also corroborated using the experimental data on several other soils reported in the literature. The proposed unified methodology alleviates the need for the determination of the Ω - s relationships which requires elaborate testing equipment that needs the supervision of trained personnel and is also time-consuming and expensive. In addition, experimental programs in this thesis provide detailed experimental data on the MR, E, qu, and soil-water characteristic curves of Canadian subgrade soils. These data will be helpful for the better understanding of the hydro-mechanical behavior of the Canadian subgrade soils and for the implementation of the mechanistic pavement design method in Canada. The simple tools presented in this thesis are promising and encouraging for implementing the mechanics of unsaturated soils into conventional geotechnical engineering practice.

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