Volumetric Properties Of Mixture Research Articles

Availability adjusted mix design method as a tool to mitigate the adverse effects of RAP on the performance of asphalt mixtures

The use of high percentages of reclaimed asphalt pavement (RAP) in asphalt mixtures offers economic and environmental advantages. However, state agencies place limits on RAP usage to avoid its indiscriminate use without a full understanding of its long-term performance implications. To achieve a more informed and rational use of higher RAP contents, it is essential to quantify recycled binder availability (RBA) and incorporate it into asphalt mixture design. The current design methods often assume complete RBA, leading to less durable mixtures. Standardized mixture design methods fail to rigorously account for the effects of RBA on the volumetric composition of asphalt mixture. Recently, the availability adjusted mixture design (AAMD) method was developed to address these issues by explicitly considering partial RBA in the interpretation of mixture volumetric properties and accounting for the role of RAP agglomerations on aggregate structure. This study tests the hypothesis that the AAMD method can mitigate the adverse performance consequences of RAP through the control of ‘available’ volumetric and effective binder properties. This was achieved by comparing virgin and RAP mixtures designed with similar ‘available’ volumetric properties according to the AAMD method. Additionally, control mixtures with RAP contents ranging from 20 to 35 percent were compared to AAMD mixtures with similar ‘available’ volumetric properties designed with the same RAP content and with 50 percent RAP. The collective results demonstrate that the AAMD method effectively mitigates negative performance consequences of RAP by controlling the ‘available’ volumetric and effective binder properties.

Effect of Mechanical Properties on Performance of Cold Mix Asphalt with Recycled Aggregates Incorporating Filler Additives

The utilization of recycled asphalt pavement in the construction and maintenance of flexible pavement with asphalt emulsion is advantageous and environmentally friendly. It saves energy due to zero heat loss during the mixing and laying of pavement compared to hot mix asphalt. Recycled asphalt pavement (RAP) is a sustainable material in place of virgin aggregates in road construction. The focus of this study is (i) virgin aggregate production, (ii) the utilization of waste material (additive), (iii) reducing the production temperature, and (iv) recycled RAP material in the pavement. This paper attempts to create a venue for using RAP greater than 50% during pavement construction. Cold mix asphalt (CMA) containing 0%, 50%, and 100% RAP materials with different dosages of cement, fly ash, and Stabil-road at 1%, 2%, and 3% of dry aggregate weight were used for ascertaining the mechanical and volumetric properties of mixtures. The mechanical properties for CMA samples, such as stability, tensile strength, moisture susceptibility, stiffness modulus, and the abrasion loss of CMA samples, were evaluated with and without RAP incorporation. Present laboratory studies revealed that a cold mix containing 50% RAP materials produced a higher stability value than the control mix, irrespective of the types of additives in its contents. All the additives can potentially resist moisture damage in the mix. Also, a significant improvement in the resilient modulus was considered for RAP-incorporated mixtures with the additives.

Influence of reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) binder availability on the composition of asphalt mixtures

Reclaimed asphalt pavements (RAP) and recycled asphalt shingles (RAS) are incorporated in the production of new asphalt mixtures to reduce cost, waste, and the consumption of virgin materials. The use of recycled asphalt materials (RAM) is limited by controlling agencies due to the uncertainties regarding their impacts on the volumetric composition and long-term performance of the asphalt mixtures. Recycled binder availability (RBA), which reflects the proportion of the recycled binder that is available to blend with virgin asphalt in an asphalt mixture, is currently neglected by the majority of mix design methods adopted by highway agencies, despite complete RBA being considered an unrealistic scenario. An incorrect assumption of the RBA in mixture design has important consequences on the inferred asphalt mixture volumetric properties, and consequently on the performance. A recently created method, so-called Availability Adjusted Mix Design (AAMD), proposes a revised interpretation of the volumetric properties of asphalt mixtures and design of the aggregate structure on the basis of partial RBA caused by agglomerations of RAM particles. The AAMD method is used in this study to evaluate the impacts of RBA on the volumetric properties of a diverse set of surface asphalt mixtures. The impacts of the RBA on the inferences of asphalt mixture composition are assessed for each mixture and the viability of using fixed RBA values for RAP and RAS sources in the state of North Carolina is assessed by comparing the inferred asphalt mixture composition yielded from the source-specific RBA versus the average RBA of the pool of recycled materials studied. The results show that the volumetric properties change considerably as a function of the assumed RBA, and the use of the AAMD becomes crucial for mixtures containing as little as 15 percent RAP and/or 4 percent or RAS. The use of a fixed RAS RBA value, calibrated as the average of a representative set of RAS stockpiles, versus the source-specific values has negligible impacts on the inferred volumetric properties of mixtures containing permissible RAS contents in North Carolina. Conversely, the use of source-specific RAP RBA values is recommended, which can be quantified through comparative sieve analysis of RAP and recovered RAP aggregate.

Determination of the Solute Content and Volumetric Properties of Binary Ionic Liquid Mixtures Using a Global Regularity of Molar Volume Expansion

Determination of the Solute Content and Volumetric Properties of Binary Ionic Liquid Mixtures Using a Global Regularity of Molar Volume Expansion

Prediction models for low-temperature creep compliance of asphalt mixtures containing reclaimed asphalt pavement (RAP)

The low-temperature creep compliances (D(t)) of asphalt mixture is one of the necessary parameters to predict the depth and amount of low-temperature cracks. Level 3 analysis in Mechanistic-Empirical Pavement Design Guide (MEPDG) software uses asphalt binder properties parameters and mixture volumetric properties to predict D(t) when the real laboratorial data is not available. However, some parameters in the model may not be routinely measured in Superpave system, which restricts the use of the prediction model. In addition, new additives and recycling materials such as reclaimed asphalt pavement (RAP) have been extensively used in recent years and shown to have significant effect on the low-temperature cracking resistance of asphalt mixture. However, the effects have not been considered in the existing D(t) prediction models. Hence, the objective of this study is to develop models with significantly high accuracy to predict the D(t) of asphalt mixtures containing RAP. A total of 1890 sets of data points were collected from three different research projects. A Pearson correlation analysis was carried out to select the input parameters which are most influential to D(t). Two prediction models (i.e., multiple linear regression and artificial neural network (ANN) models) were proposed. A comprehensive analysis on the prediction accuracy and reasonability of the proposed models was conducted. The results showed that the proposed models had much better prediction performance with high accuracy than the existing models. The comparisons between the proposed models with the existing models confirmed that it is necessary to take the new additives and recycling materials into account in developing D(t) prediction models.

Predictive Artificial Neural Network Laboratory Fatigue Endurance Limit Model for Asphalt Concrete Pavements Based on the Volumetric Properties and Loading Conditions

Asphalt concrete healing is one of the important concepts related to flexible pavement structures. Fatigue endurance limit (FEL) is defined as the strain limit under which no damage will be accumulated in the pavement and is directly related to asphalt healing. Pavement section designed to handle a strain value equivalent to the endurance limit (EL) strain will be considered as a perpetual pavement. All four-point bending beam fatigue testing results from the NCHRP 944-A project were extracted and utilized in the development of artificial neural network (ANN) EL strain predictive model based on mixture volumetric properties and loading conditions. ANN model architecture, as well as the prediction process of the EL strain utilizing the generated model, were presented and explained. Furthermore, a stand-alone equation that predicts the EL strain value was extracted from the developed ANN model utilizing the eclectic approach. Moreover, the EL strain value was predicted utilizing the new equation and compared with the EL strain value predicted by other prediction models available in literature. A total of 705 beam fatigue lab test data points were utilized in model training and evaluation at ratios of 70%, 15%, and 15% for training, testing, and validation, respectively. The developed model is capable of predicting the EL strain value as a function of binder grade, temperature, air void content, asphalt content, SR, failure cycles number, and rest period. The reliability of the developed stand-alone equation and the ANN model was presented by reasonable coefficient of determination (R2) value and significance value (F).

Thermophysical and volumetric properties of mixtures {carvacrol + ethanol} at several temperatures and atmospheric pressure

Experimental molar heat capacities at atmospheric pressure have been determined for the mixture {carvacrol + ethanol} every 10 K in the temperature interval (298.15–328.15) K and over the entire composition range with a Calvet type calorimeter. Densities, necessary for determining isobaric heat capacities, and ultrasonic speed of sound have been also measured at the same conditions. From these properties isobaric thermal expansivities, isentropic compressibilities, isothermal compressibilities, internal pressures and isochoric molar heat capacities have been calculated. Furthermore, in order to complete our thermophysical study the corresponding excess properties have been calculated and discussed in terms of molecular interactions. Finally, excess molar isobaric heat capacities have been calculated with COSMO-RS and compared to the experimental values.

Effect of Crumb Rubber as Fine Aggregate Replacement in Cold Mixture Asphalt

The number of waste tires has been increasing as an impact of rapidly growing number of vehicles and becomes a global environmental concern. The environmental impact can be reduced by converting the waste tires to crumb rubber and reusing it as a replacement of fine aggregates in asphalt mixture. Dense graded cold mixtures asphalt design was developed for rubberized mixtures with up to 100% (by weight) crumb rubber replacement. Series of laboratory testing were performed for evaluating the Marshall stability and volumetric properties of rubberized cold mixture asphalt. The findings of this laboratory study indicated that Marshall stability and volumetric properties of these mixtures were affected by crumb rubber percentage. Although the use of crumb rubber in cold mixture asphalt could decrease the mechanical and volumetric properties of mixtures, but still has a great potential as a partial fine aggregate replacement in cold mixture asphalt. Rubberized cold mixture asphalt could be considered as a flexible pavement subjected to low traffic medium load.

Estimating asphalt mixture volumetric properties using seemingly unrelated regression equations approaches

As the asphalt pavement industry seeks to manufacture products with low variability, advances in modeling approaches that help optimize asphalt materials are lagging behind. Typically, well-controlled paving projects provide asphalt mixture volumetric properties with low variability, while poorly controlled projects result in higher variability in asphalt mixture volumetric properties. Additionally, on many occasions, the management of all the factors influencing asphalt mixture production and construction is inadequate. The work described in this paper demonstrates that seemingly unrelated regression equations (SURE) approaches can be used to estimate asphalt mixture volumetric properties using mixture design, material properties, and testing inputs. SURE approaches can help evaluate asphalt mixture production and placement by accounting for the deficiencies and limitations in quality assurance data. Moreover, SURE approaches analyze asphalt mixtures in a concise, yet robust, manner. The findings of this study contribute to a better understanding of variability in asphalt material production and placement.

Effect of rejuvenator types and mixing procedures on volumetric properties of asphalt mixtures with 50% RAP

The use of Reclaimed Asphalt Pavement (RAP) in asphalt mixtures has several benefits, such as reducing the consumption of virgin materials and protecting the environment. However, as high RAP content (e.g., 50%) is used, asphalt mixtures become brittle so that premature failure (cracking) may occur. To improve the cracking resistance of asphalt mixtures with high RAP contents, one of the approaches considered is the use of rejuvenators. Such rejuvenators, when used in high RAP asphalt mixtures, counteract the effects of the aged RAP binder and may have an impact on the volumetric properties of the mixtures. The objective of this study is to evaluate the effect of rejuvenator types and mixing procedures on the volumetric properties of asphalt mixtures prepared with high RAP content (i.e., 50%). To achieve this objective, three rejuvenators and three rejuvenator mixing procedures were utilized to prepare asphalt mixtures containing 50% RAP. Volumetric properties of the mixtures (air voids (AV), voids in mineral aggregate (VMA), and dust to binder ratio) were determined. Testing results indicate that some volumetric properties of mixtures (AV and VMA) could significantly change when different mixing procedures and rejuvenator types were used. Therefore, the mixing procedures and the rejuvenator types should be taken into considered when conducting mixture design.

Effects of Reheating Procedure and Oven Type on Performance Testing Results of Asphalt Mixtures

Reheating and oven-aging procedures of plant-produced asphalt mixtures in laboratories are important topics to consider as performance testing of mixtures becomes more popular among agencies. Differences between laboratory equipment and procedure could significantly affect performance properties. The objective of this study is to investigate the influence of sample size, oven type, and variation in reheating/aging temperatures on the results of two performance tests on plant-produced mixtures. A selected mixture was tested for volumetric properties and performance using Hamburg wheel-tracking (HWT) and semi-circular bending (SCB-IFIT) tests. Results show that reheating mixtures uncovered and in smaller containers could significantly reduce the time to achieve aging temperature, and could make the process more efficient and consistent. In addition, aging using three different oven types showed that temperature within ovens can vary significantly depending on the location of the sample inside the oven, which affects the time required to reach the target temperature, and thus may also influence the aging of the sample. The mixture volumetric properties show that the effect of various heating conditions is marginal. Using the developed reheating/aging procedure of this study, the results of the HWT and SCB-IFIT tests showed no substantial effect of oven type on rutting and cracking resistance. The overall results indicate that there is a need to standardize the conditions of reheating, sample geometry, and to verify uniformity of temperature in ovens. Such standardization can further reduce variability and thus should be part of the AASHTO/ASTM standard procedures for quality control, or of laboratory equipment calibration procedures.

Evaluation of Asphalt Mixture Containing Coal Ash

As the first time in Korea, bottom ash which is by-product of coal ash in power plant was recycled as fine aggregates in hot mix asphalt (HMA) mixtures. The bottom ash was used to replace the fine aggregate of HMA by various portions of fine aggregate which is passing 4.75mm sieve, at the ratio of 10%, 20%, and 30%. Leaching test was performed to measure the concentration of toxicity in the bottom ash. The optimum asphalt content was measured for each portion of bottom ash used as fine aggregate using by Marshall mix design method. Stability, flow value, and mixture volumetric properties were compared to verify the applicability of bottom ash as fine aggregate in HMA. The moisture susceptibility and fatigue cracking resistance of asphalt mixture containing bottom ash and fly ash was investigated. It is concluded that coal ash can be efficiently used as fine aggregates in asphalt mixture.

Optimization of asphalt and modifier contents for polyethylene terephthalate modified asphalt mixtures using response surface methodology

Optimization of polymer and asphalt content in polymer modified asphalt mixture is the aim of road engineers and designers. The purpose of this study is to characterize Stone Mastic Asphalt (SMA) mixture’s properties containing waste polyethylene terephthalate (PET) which is a type of polymer material. Response Surface Methodology (RSM) was designated as a new method to measure mixture properties at different PET content and asphalt binder value. To fabricate the mixture fresh 80/100 penetration grade asphalt binder with different percentages (5–7% by weight of aggregate particles) was utilized. Different amounts of PET were used from 0% to 1% by weight of aggregate particles. Marshall Stability and Flow test was performed on the mixtures. Specific gravity and volumetric properties of mixtures were obtained. RSM was used to analyze Marshall and volumetric properties of unmodified and PET modified asphalt mixtures. Models were produced to fit the experimental results. As shown in this study suggested models were successfully fitted to the experimental results. Based on the results achieved amounts of 5.88% of asphalt content and 0.18% of PET were found to be the optimal values.

Density of Mixtures Containing Sugars and Ionic Liquids: Experimental Data and PC-SAFT Modeling

The potential use of ionic liquids (ILs) for biomass and carbohydrate processing has been discovered in the past decade. Many advantages have been pointed out in their application for biorefining purposes. The phase equilibria and volumetric properties of mixtures containing ILs and biomass-derived compounds such as sugars or sugar alcohols are relevant for process design. In this work, the density, at atmospheric pressure, of binary mixtures containing sugars (glucose and fructose) or sugar alcohols (xylitol and sorbitol) and ionic liquids (1-ethyl-3-methylimidazolium ethylsulfate and Aliquat336) is presented within large temperature (278 K to 343 K) and composition ranges (up to sugar or sugar alcohol mass fraction of 0.30). The density data followed a bilinear trend with respect to temperature and composition. The data were therefore represented using planar regression with a very good accuracy, average relative deviation (ARD) < 0.1 % in most of the cases. The perturbed-chain statistical association f...

Flow number predictive models from volumetric and binder properties

This study was conducted to develop flow number (FN) predictive models for asphalt concrete mixtures (AC) using Superpave volumetric and binder properties. The FN test is the recommended procedure for evaluating rutting resistance of AC mixtures under the AASHTO mechanistic empirical pavement design guide (MEPDG). FN tests were conducted at 54°C on 13 plant-produced laboratory-compacted AC mixtures using repeated creep loads of magnitude 206kPa for 10,000cycles or until an accumulated strain of five percent. The results were compared with key Superpave mixture volumetrics and binder specification parameters. First-order multiple regression models were developed to describe the relationship among FN, mixture volumetrics, and Superpave rutting parameter (G*/sinδ). The results showed that FN was strongly correlated (R2=0.94) to G*/sinδ, effective binder content, air voids, and dust to effective binder ratio. The results demonstrate a clear link between FN and mixture volumetric and binder properties and suggest FN could be considered as potential rutting specification parameter for QC/QA purposes in the field. The results may also be useful for optimizing the laboratory mix design process by directly relating certain Superpave specification parameters to mixture rutting resistance.

Microstructural analysis of asphalt mixtures using digital image processing techniques

In this paper, the internal microstructure of asphalt mixture is analyzed through digital image processing (DIP) of two-dimensional asphalt mixture images. A set of 12 mixtures prepared with two binders, two air voids percentages, and different recycled asphalt pavement (RAP) contents is used. First, small asphalt mixture beams of the same size of bending beam rheometer specimens are prepared for the images acquisition. Then, based on mixture volumetric properties, a three-phase material model is obtained. Finally, 2- and 3-point correlation functions of the material phases are numerically evaluated. No significant differences were observed in the microstructure and spatial distributions of aggregates, asphalt mastic, and air voids for asphalt mixtures containing up to 40% of RAP. However, an increase in auto correlation length (ACL) was found for RAP mixtures in comparison with the conventional mixtures.

Influence of Laboratory Mixing Procedures on Volumetric and Mechanical Properties of RAP Mixtures

Abstract The primary goal of this study was to assess the effectiveness of specific laboratory mixing procedures in simulating the production of plant-produced hot mix asphalt (HMA) mixtures with high reclaimed asphalt pavement (RAP) content. Three distinct methods for incorporating the RAP material into the mixing process were examined. The first method consisted of heating and mixing the virgin aggregate, virgin asphalt binder, and RAP material at the appropriate mixing temperature for the virgin asphalt binder. The second method consisted of superheating the virgin aggregates according to the National Asphalt Pavement Association (NAPA) recommendations, with the virgin asphalt binder heated to the appropriate temperature and the RAP material introduced dry and at the ambient temperature. Last, the third method was similar to the second procedure with the exception of adding the RAP material wet at the ambient temperature. Mixing temperatures were examined over the duration of the mixing process for each method. This provided insight into how effectively the virgin aggregate is transferring heat to the RAP material. Additionally, a short-term oven-aging analysis was utilized to determine the appropriate aging time in the laboratory to replicate the aging experienced by the plant-produced mixtures. Last, compacted samples were created for each mixing method, as well as for the plant-produced laboratory-compacted mixtures, to analyze the volumetric properties and mechanical properties using the dynamic modulus. Based on the data generated in this study, the most appropriate method was recommended to be instituted in the laboratory for mixing HMA mixtures containing RAP material because of its simplicity and its close results to the plant-produced mixtures.

A Simple Equation for Predicting the Volumetric Properties of Mixtures Involving Ionic Liquids

A simple equation has been employed to predict the volumetric properties of binary mixtures involving an ionic liquid. Moreover, we have calculated excess volumetric properties of the studied mixtures using the proposed equation. The outcomes of our computations have been compared with experimental data. The reliability of the proposed model was checked by taking 854 experimental data points over a temperature range from 278 to 358 K; the average absolute deviation of the calculated density and the excess molar volume were found to be 0.50 and 0.80 %, respectively, while the accuracies of our calculations were of the order of ±3 %.

Comparative evaluation of hot-mix asphalt design methods

This study was done to evaluate superior performing asphalt pavements (Superpave) mixture design using local materials in Malaysia. Comparison was also done with the conventional Marshall method-designed mixture conforming to the specifications of the Malaysia Public Works Department (PWD). The experimental plan consisted of a matrix involving one granite aggregate source, two different aggregate gradation and two different asphalt binder types. Local granite aggregates being produced presently were found to conform to the consensus and source aggregate properties criteria of the Superpave mixture design system. Mixture volumetric properties showed that Superpave-designed mixture uses less asphalt binder than the PWD Marshall mixture. Rutting and moisture susceptibility tests showed that Superpave-designed mixtures are more resistant to rutting and moisture damage compared with the PWD mixture. Mixture characterisation tests showed that Superpave mixtures have higher stiffness than the PWD mixture. These indicate that Superpave-designed mixtures are superior to the PWD Marshall-designed mixture.

Volumetric Properties of Binary Mixtures of 2,4,6-Trimethylpyridine with 1,2-Ethanediol, Methanol, and Water, and the Association Energies of the O–H· · ·N Bonded Complexes

2,4,6-Trimethylpyridine forms 1:1 complexes with methanol, 1,2-ethanediol, and water due to the O–H· · ·N bonds. The association energy of the complexes was calculated using MP2 and DFT methods. The complexes with 1,2-ethanediol and water aggregate in the liquid phase as a result of the O–H· · ·O bonds. In spite of the higher O–H· · ·N bond energy, the aggregation of the ethanediolic complexes is less pronounced than that of the aqueous ones. That is probably caused by the weaker induction effect due to the C–C chain separating the hydroxyl groups in the diol molecule. Aggregation is impossible in the methanolic system, because of the lack of proton-donating functional groups. Differences in the hydrogen bond energy and in the ability to aggregate are manifested in the volumetric properties of the mixtures.