Julian Mills-Beale

A Wireless, Passive Embedded Sensor for Real-Time Monitoring of Water Content in Civil Engineering Materials

A wireless, passive embedded sensor was applied for real-time monitoring of water content in civil engineering materials such as sands, subgrade soils, and concrete materials. The sensor, which comprised of a planar inductor-capacitor (LC) circuit, was embedded in test samples so that the internal water content of the samples could be remotely measured with a loop antenna by tracking the changes in the sensors resonant frequency. Since the dielectric constant of water was much higher compared with that of the test samples, the presence of water in the samples increased the capacitance of the LC circuit (capacitance of the capacitor was proportional to the dielectric constant of the medium between its electrodes), thus decreasing the sensors resonant frequency. Using the described sensor, a study was conducted to investigate the drying rate of sand samples of different grain sizes. A study was also conducted to measure the curing rate of a portland cement concrete slab during casting, and its drying rate after it has been soaked in water. The described sensor technology can be applied for long-term monitoring of localized water content inside soils and sands to understand the environmental health in these media. In addition, this sensor will be useful for monitoring water content within concrete supports and road pavements. The measurement of water content is important for civil engineering infrastructure since excess water may hasten their degradation.

Evaluation of Low-Temperature Binder Properties of Warm-Mix Asphalt, Extracted and Recovered RAP and RAS, and Bioasphalt

This research project evaluates the low-temperature performance of energy-efficient and environmentally friendly hot-mix asphalt (HMA) paving materials. Innovative materials gaining interest in the asphalt pavement industry includes warm mix asphalt (WMA), recycled asphalt shingle (RAS), reclaimed asphalt pavement (RAP), and bioasphalt. The materials are used as modifiers in typical HMA to enhance low-temperature field performances. Sasobit compounds at 0.5, 1.0, and 1.5%, by weight of performance grade (PG) 52-34 asphalt binder, are used to design the WMA. Five and 10% of RAS were also added to a PG 52-34 asphalt binder. 50% of RAP combined with 50% of the base PG 58-28 binder, and 100% RAP extracted from the PG 58-28 HMA, were prepared and tested. Bioasphalt was produced from swine waste and used to modify PG 64-22 asphalt binder. By using the Superpave bending beam rheometer (BBR) and the new asphalt binder cracking device (ABCD) method, the thermal cracking performance of the samples were tested. The ...

Asphalt binders blended with a high percentage of biobinders: Aging mechanism using FTIR and rheology

AbstractThe objective of this study is to characterize the rheological properties and aging mechanism of asphalt binders blended with high percentages of biobinders using Fourier transform infrared spectroscopy (FTIR). The petroleum asphalt was partially replaced by the biobinders at fractions of 30 and 70% by weight. Rotational viscometer (RV) and dynamic shear rheometer (DSR) tests were conducted for the rheological properties, and the rolling thin film oven (RTFO) test was conducted for the aging simulation. Loss of volatiles was obtained from the RTFO test, whereas the oxidation characterization was investigated through the FTIR test. The rheology results showed that the bioblended asphalt binder exhibit different rheological properties as compared with the control asphalt binder before and after the RTFO-aging. The mass loss test showed that the loss of volatiles of biobinders were much higher than the control asphalt binder. FTIR spectra analysis showed that additional C═C, C─O, C═O and OH bonds wer...

Review of advances in understanding impacts of mix composition characteristics on asphalt concrete (AC) mechanics

The overall performance of an asphalt concrete (AC) mixture is dependent on its composition including the properties, proportions and distributions of the ingredients. For existing asphalt mix design methods, however, there is a missing link between the mix composition and the overall properties and performance. To improve the fundamental understanding of AC mixtures, this paper presents a comprehensive review of the advances in understanding the mix composition characteristics and their impact on AC mechanics. This review focused on the links between the mix composition and the overall properties. The review contains a brief background of this study, followed by a discussion of four typical mixture composition characteristics, namely aggregate size, aggregate morphology, asphalt matrix time-dependent properties and anisotropic AC microstructural characteristics. Furthermore, three types of methods were reviewed for understanding the links between the composition characteristics and the AC behaviours: the experiment-based methods, multiphase micromechanical models and numerical models. The numerical models include discrete element models and finite element models. Finally, a brief summary and further research needs are provided.

Evaluation of Asphalt Blended With Low Percentage of Carbon Micro-Fiber and Nanoclay

The objectives of this study are to investigate the applicability of carbon micro-fiber and nanoclay in asphalt binders and to evaluate the performance of micro- and nano-modified asphalt (NMA) binders in terms of rheological properties. Due to their unique characteristics, micro- and nanomaterials were hypothesized to play a critical role in enhancing the performance behavior of asphalt binders. In light of existing research, carbon micro-fiber (MCF) and Nanomer I.44P (NI.44P) were selected as the micro- and nanomaterials for this research. Then, these materials were added into the PG 58-34 control asphalt binder at the concentrations of 2 % and 4 % by weight. Superpave™ binder tests—rotational viscosity (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR)—were then conducted for evaluating the performance of each modified asphalt binder. Also, the characterization tests were run on the aged samples prepared using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) to simulate the short-term and long-term aging. Subsequently, the viscosity, dynamic shear modulus (|G*|) and phase angle (δ) of asphalt binders were analyzed, and the dissipated energy per load cycle was introduced to estimate the asphalt binders’ rutting and fatigue cracking resistance. It was found that the dynamic shear modulus of asphalt binders can be improved by the selected micro- and nanomaterials. Furthermore, the NI.44P modified asphalt showed better properties relative to the other modified asphalt binders or the control (PG 58-34) binder.

Properties of Recovered Asphalt Binder Blended with Waste Engine Oil: A Preliminary Study

It is universally known that the use of recovered binder in asphalt pavements results in a stiffer asphalt mixture. One sustainable material that holds immense potential in softening the stiffened mixture is waste engine oil. Large quantities of the waste engine oil on pavements are undesirable due to the damage it imposes on the asphalt pavement. However, small amounts of the waste oil within the binder and mixture may improve the recovered binders performance characteristics since the stiffer asphalt may be softened. The objective of this paper is to characterize the effects that waste engine oil has on binders blended with aged bitumen, such as asphalt binder from reclaimed asphalt pavements (RAP). This paper will present the results of blended aged asphalt binder with virgin binder, and subsequently combine the mixture with waste oil. After the addition of the waste engine oil, the G*/Sin(δ) parameter is analyzed which indicated that the asphalt became softer. The viscosity decreased with the addition of waste engine oil. The use of waste engine oil may therefore create conditions of better thermal cracking (low-temperature) behavior and allow for easy mixing, handling and compaction.

Determination of Flow Number in Asphalt Mixtures from Deformation Rate During Secondary State

Numerous research studies have been conducted on the connection between asphalt material properties and pavement performance. Asphalt mixture performance tests (AMPTs) have been part of these efforts in the past few years. One such test is the flow number test, the output of which is the flow number. Recent studies have found that flow number correlates well with the rutting potential of asphalt pavement. However, the current method used in AMPTs to examine the flow number also was highly sensitive to the variation of testing data (resulting in inaccurate flow number values) and time-consuming, especially when used on stiff asphalt mixtures. The main goal is to determine the flow number with the use of the deformation rate at the secondary state from the result of the flow number test. One hundred twenty-two flow number tests were conducted. A stepwise method was used to overcome variations in results from the flow number test. The flow number was determined with the stepwise method, then compared with the flow deformation rate. A strong correlation between flow number and deformation rate was found. Therefore, the deformation rate can be used to estimate flow number, which significantly reduces testing time. The proposed method also allows the flow number test to be terminated as soon as the permanent strain reaches 1.2%.

Postprocessing Method for Dynamic Modulus Tests of Hot-Mix Asphalt

The main objectives of this study are: (1) to develop a postprocessing method for analyzing the dynamic modulus test of compacted asphalt mixtures; (2) to identify optimum regression equations for the compressive stress and its corresponding strains in a dynamic modulus test using this method; and (3) to evaluate the accuracy of the proposed method compared with the method in the current equipment specification. Including the procedure used in the current equipment specifications, two procedures for fitting the dynamic stresses and three procedures for fitting the corresponding strains were employed in the postprocessing method. The coefficients of the regression equations in the five procedures were used to determine the dynamic modulus and phase angle. Uniaxial compressive dynamic modulus tests of 10 asphalt mixtures were conducted at five temperatures and six frequencies with Universal Test Machine (UTM). A total of 1,800 test results were processed with the procedures in the proposed method. On basis of the standard errors of the least square fit, the procedures in the postprocessing method were evaluated. It was found that the procedure in the equipment specification was inaccurate to fit the strains, especially at the higher temperatures and low frequencies. Therefore, correction coefficients were recommended for the measured dynamic modulus and phase angle from the currently used UTM. The potential application of the proposed method is significant since it will improve the degree of accuracy of the dynamic modulus values used in the mechanistic-empirical pavement design procedure.

Low Temperature Cracking Potential of Aged Asphalts Using Simulated Aging Techniques

The objective of this paper is to characterize low temperature properties of recycled asphalt pavements (RAP) binders and artificially-aged asphalt binders. The Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) were used to artificially age the asphalt binders with the binder undergoing up to three PAV aging cycles. Low temperature asphalt binder properties were investigated using the Asphalt Binder Cracking Device (ABCD). RAP binder specimens included a 50% RAP binder blend with a virgin PG 58-28 control binder. The ABCD determined the strain jump indicating the temperature where asphalt binder thermal cracking occurred. An average 5.9% difference in thermal cracking temperature was observed when comparing the control binder versus artificially-aged binders. Conclusions reached from this investigation are that RAP binder thermal cracking temperature and strain increases with additional amounts of RAP binder and RAP binder thermal cracking temperatures were similar to one or two PAV aging cycles.

Measuring the Specific Gravity and Absorption of Steel Slag and Crushed Concrete Coarse Aggregates: A Preliminary Study

The research objective is to evaluate a new test procedure for determining the specific gravity and absorption of steel slag and crushed concrete, which are recycled and manufactured coarse aggregates, respectively. Steel slag and crushed concrete, unlike many coarse aggregates possess special physical characteristic such as many effective surface voids. It is hypothesized that the current AASHTO T 85 (24±4 hours) test method fails to adequately saturate these effective voids on the coarse aggregate surfaces. When the steel slag and crushed concrete were soaked for 36 and 48 hours, it underscored the fact that AASHTO T 85 underestimates the absorption capacity of special porous coarse aggregates. A new proposed vacuum saturation approach is thus utilized to suck the trapped air within the effective pores while replacing it with water. This method is expected to better determine the specific gravity and absorption of these special aggregates. The steel slag and crushed concrete were tested at 30 minutes of vacuum saturation under 30mm Hg pressure. Statistical analysis indicated that this proposed method was viable in determining the specific gravities and absorption of these aggregates. An extended research is ongoing to expand the scope of coarse aggregates in addition to testing at reduced saturation times to increase the efficiency of the proposed method.