Transport Research International Documentation (TRID)

New Design Method of Asphalt Mixtures Considering Uncertainty

Thu, 27 Jun 2019 14:54:00 GMT

The existing methods of asphalt mixture design are deterministic and rely only on the means of design parameters, such as unit weight and volumetric properties. This article presents a new design method of asphalt mixtures that considers the uncertainties of the measured properties and the calculated design parameters, represented by the coefficient of variation (CV). The uncertainties of the measured properties (typically CV < 1 %) propagate through the calculations and could result in high uncertainties in the calculated design parameters (e.g., CV?>?40 %) that make them unreliable. The proposed method is developed in the context of the Marshall mix-design method and is applicable to the Superior Performing Asphalt Pavements method with minor modifications. The Taylor series expansion was used to develop the moments (mean and standard deviation) and CV of the calculated design parameters. The developed formulas were verified using Monte Carlo simulation. Criteria for sample acceptance are then presented based on the uncertainties of the design parameters. The uncertainty information is then used to establish confidence intervals for the design parameters, determine the optimum asphalt content, and compare the results with project specifications. Sensitivity analysis of the mix-design parameters is conducted, and practical implications are discussed. Numerical examples are presented to demonstrate the application of the proposed method. The proposed method takes the design of asphalt mixtures one step further toward a reliable performance-based design. As such, the method should be of interest to pavement engineers and practitioners.

Experimental evaluation of rice husk ash and fly ash as alternative fillers in hot-mix asphalt

Fri, 29 Mar 2019 10:15:19 GMT

Ever-growing concern to protect the environment concentrated the attention of the society on the possible re-use of different agricultural and industrial wastes in road construction. This research study depicts the effect of using wastes like rice husk ash (RHA) and fly ash (FA) as a replacement of conventionally used hydrated lime (HL) as fillers in hot-mix asphalt (HMA). Primarily, the dense graded bituminous macadam (DBM) mix specimens were made in the laboratory with varying proportions ranging from 2% to 8% of HL, RHA and FA by following design mixes according to the Marshall method and compared the results with control mix as prepared by utilising 2% HL. The performances of the said mixes were studied through the Marshall quotient, indirect tensile strength and tensile strength ratio. Results of investigation show better performance of HMA with the addition of RHA and FA and also proved to be economical as the optimum bitumen content is reduced by 7.5% from that of control mix when added at 4% filler ratio. Further, RHA shows a greater affinity to the bitumen attributing the highest stiffening effect of the bituminous mastic droplets compared to that of other used fillers with good compatibility at the micro level by satisfying the essential criterion.

Development of a New Asphalt Mixture Containing Reacted and Activated Rubber and Reclaimed Asphalt Pavement via Superpave Mix Design and Marshall Mix Design

Sat, 02 Mar 2019 15:41:12 GMT

Reacted and Activated Rubber (RAR) is one of the pre-treated crumb rubber technologies. It has been developed as a new approach to produce crumb rubber modified asphalt mixture in the field. However, most of the previous studies are limited to the Marshall design method to obtain the optimum asphalt content. Further, none of these studies tried to add reclaimed asphalt pavement (RAP) to the RAR modified asphalt mixtures. The objective of this study was to conduct a Superpave mix design for determining the optimum asphalt content of asphalt mixture with RAR and RAP, and analyze the performance of RAR modified binder and mixture through a series of laboratory tests. Performance Grade (PG) 58-28 binder was used for this study. Both the Superpave mix design method and the Marshall mix design method selected the optimum asphalt binder content as 11.0% by weight of the mixture, where the virgin binder content was 6.6% and the RAR content was 4.4%. In general, the test results were favorable in rutting resistance performance and moisture resistance. The designed RAR modified mixtures will be used to construct trial sections in early August 2018 in Kalamazoo, Michigan.

Performance Evaluation of Super-Pave and Marshall Mix Design to Suite Indian Climatic and Traffic Conditions

Tue, 20 Nov 2018 10:11:57 GMT

In India, presently the bituminous mixes are designed based on empirical laboratory procedures i.e. Marshall method of mix design without simulating the actual field conditions. This has led the highway engineers to think of a performance based mix design method, which can predict the fundamental properties of bituminous mixes such as rutting and fatigue. The primary objective of the performance based mix design method to establish the appropriate amount of binder content in the mix that will simultaneously satisfy the rut resistance and fatigue cracking requirements for given traffic and environmental conditions. This lead to development of Superior performance pavements (Super-pave) mix design by Strategic Highway Research Program (SHRP), USA. The main objective of the study is to develop performance based mix design for Indian conditions using Super-Pave Gyratory compactor (SGC) and compare the Super-pave asphalt mixture design procedures with the Marshall Asphalt mixture design method. The comparison was based on several issues including evaluation of materials prior to mixture design, the design asphalt content, and the relationship between mixture design and pavement performance. After comparison between mix design methods resilient modulus of different bituminous mixes prepared with conventional as well as modified binder, are evaluated at different temperature. For performance deformation of mixes, flow number test is performed through Asphalt Mixture Pavement Tester (AMPT) at varying air voids and at different deviator stress level. It is found that the performance parameters such as ITS, TSR, Resilient modulus and Flow number values are higher in case, sample prepared by Super-pave mix design method as compare to those sample prepared by Marshall method of mix design.

A Study of Moisture Damage in Warm Mix Asphalt Concrete with Reclaimed Asphalt Pavement

Mon, 27 Aug 2018 14:04:11 GMT

Currently, many methods and technologies have been introduced to reduce new material usage and energy consumption. One approach is using reclaimed asphalt pavement ( RAP) as renewable material which allows natural resources conservation. Moreover, applying warm mix asphalt (WMA) technology can reduce energy consumption comparing to hot mix asphalt (HMA). One of the major concerns with WMA is moisture sensitivity which causes more chance of stripping occurrence. The aim of this study is to investigate moisture sensitivity of WMA with four RAP proportions (0% , 20% , 35% and 50% ) comparing to HMA. Effect of two additive types (Sasobit® and Advera®) and two lower mixing temperatures (150°C and 130°C) on the moisture damage were also evaluated. Results from this study show that the Sasobit® modified WMA with 35% and 50% RAP have high moisture damage resistance as indicated with TSR greater than 80%. for both 150°C and 130°C mixing temperatures.

Evaluation of Impacts of Allowing Heavier Log Loads in Northern Wisconsin During Spring Thaw

Mon, 28 May 2018 09:48:59 GMT

This study investigated the impact of a January 1, 2011 Wisconsin statutory change (RS permit law) that allows vehicle combinations up to 98,000 pounds on six axles to transport loads of raw forest products during the spring-thaw suspension period. Prior to the statutory change, Wisconsin Department of Transportation (WisDOT) could suspend overweight permits for the transportation of raw forest products during the spring thaw, or impose special weight limits on highways. The specific goals of the investigation were to: (1) determine if there is an impact with this statutory change; (2) identify whether certain vehicle classes or categories are more damaging than others, and the possibility of lessening the impact of these heavy loads; and (3) determine if certain pavements are impacted with increased loads due to the policy change. A total of eleven pavement segments were analyzed in the study and fell into two paved surface categories: older Marshall mix design (4 segments) and newer Superpave mix design (7 segments). The analyses showed that the Superpave mix design segments generally produced better performance than the Marshall mix design segments. Higher levels of alligator cracking and rutting were associated with the Marshall mix segments compared to the Superpave segments. Levels of longitudinal cracking were, however, not significantly different between the two mix types. A segment by segment analysis revealed that one Marshall mix segment (age 13 years) exhibited significantly higher rates of progression in alligator and longitudinal cracking in the loaded lane when compared to the adjoining empty lane. Hence, the rehabilitation or replacement of older Marshall segments within the logging route network is needed to allow up to 98,000 pounds of raw forest products to be transported on six-axle vehicles, while inflicting lesser damage to the pavement network. In addition, this study was initiated just one year after the implementation of the RS Permit law and focused on only a few segments. A longer time frame and many more segments may be needed to help evaluate the overall long-term impacts from log loaded trucks, or a field test consisting of a special test section could be constructed and subject to the RS permit law trucks to capture their overall impact during the spring-thaw season. Federal Highway Administration (FHWA) vehicle classes 9 and 10 were the main carriers of logs throughout the studied network. The relative-log carrying efficiency (with reference to the pavement damage caused) of class 10 trucks averaged approximately 22,000 lb/ESAL (equivalent single axle load) compared to 15,400 lb/ESAL for class 9 trucks. A considerable proportion of trucks was found overloaded at two platform scales, averaging 31% and 24% in the winter, and 25% and 33% during the spring. The magnitude of the truck overload, however, averaged less than 5% of the 98,000-lb limit permitted under the law for gross vehicle weight.

Experimental Study on Performance of Asphalt Mixture Designed by Different Method

Wed, 10 Aug 2016 11:05:48 GMT

In order to explore the Marshall, Superpave and Gyratory Testing Machine (GTM) methods, the similarities and differences of the three design methods are studied in detail. Experimental study on performance of asphalt mixtures AC-13, AC-20 and AC-25, designed by different methods, was executed in this paper. Test results show that the GTM method gives lower void and lower bitumen aggregate ratio than the other two methods; it has much better water stability and high-temperature stability. The dynamic stability (DS) value is 3256/mm by GTM design method, which is 1.91 times that of the Marshall method and 1.33 times that of the Superpave method. Superpave method gives lower bitumen aggregate ratio than Marshall method. The asphalt mixture designed by the Superpave method has longer fatigue life than the mixture designed by the other two methods. The volume parameters of asphalt mixture designed by the Marshall method can conform to specification very well, but the performance of asphalt mixture seems to be worse than the other two methods.

Effect of Using Cement and Fly Ash as Filler Materials on the Marshall Properties of Bituminous Concrete Mix

Fri, 01 Jul 2016 17:06:44 GMT

An ideal bituminous mix is expected to result in a mix which is adequately strong, durable and resistant to fatigue and permanent deformation and at the same time environmentally friendly and economical. Bituminous mix design is a delicate balancing act among the proportions of various aggregate sizes and bitumen content. For a given aggregate gradation, the optimum bitumen content is estimated by satisfying a number of mix design parameters. Fillers play an important role in engineering properties of bituminous paving mixes. Conventionally cement and non-conventionally fly ash is used as filler materials. In the present study an attempt has been made to assess the influence of using filler material on Marshall properties of bituminous concrete mix. Optimum bitumen content was determined by adopting the Marshall method of bituminous mix design, and then mix properties were determined using cement and fly ash as filler material at optimum bitumen content. From the test results obtained, it was observed that bituminous concrete mix prepared using cement has higher stability and lesser optimum bitumen content, flow, voids filled with bitumen (VFB), voids in the mineral aggregate (VMA) values when compared with bituminous concrete mix prepared using flu ash as filler material.

Experimental Studies on Warm-Mix Asphalt Using Additives

Thu, 04 Feb 2016 08:37:31 GMT

In the present research work, it is attempted to check the performance of a Bituminous Concrete (BC) mix and Dense Bituminous Macadam (DBM) mix with respect to stability, tensile strength and rutting characteristics after adding additives with VG-30 and VG-10 grade bitumen, respectively. Warm-Mix Asphalt (WMA) offers many significant advantages such as energy savings, decreased emissions and fumes, decreased binder aging and extended paving season into the cold winter months located at high altitudes. The Marshall method of mix design procedure is adopted to determine the stability and flow characteristics of BC and DBM mixes. The binder content for the aggregate and bitumen used is determined by performing a density-air voids and stability-flow analysis on cylindrical specimens batched, mixed and compacted in the laboratory. The WMA process utilizes Sasobit and Zycotherm as additives which improves stability, tensile strength and reduces rutting. Immersion wheel trafficking test method is adopted to check the rutting characteristics of specimens which have been prepared by varying the mixing temperatures and by adding additives. In this work, WMA is designed for both BC and DBM mixes, respectively, with addition of additives to obtain results of Marshall, indirect tensile strength and rutting tests.

Mix Design and Moisture Susceptibility of Asphalt Concrete Mixes Containing Waste Catalyst from Oil Refineries

Mon, 18 Jan 2016 16:36:34 GMT

The main objective of this study was to investigate the potential of using spent catalysts produced from the process of refining crude oil as a constituent material in hot mix asphalt (HMA). Two types of spent catalyst, equilibrium catalyst (ECat) and zeolite catalyst (ZCat), were used to partially replace some selected sizes of aggregate in the HMA. Chemical analysis of the raw catalysts indicated that both catalyst types used in this study were comprised mainly of Al₂O₃ and SiO₂. Marshall Method of mix design was followed to determine the optimum asphalt content of the aggregate structure containing waste catalyst. Volumetric and stability data indicated that there is a good potential for using spent catalyst in road applications. Environmental analysis and moisture damage potential were also carried out to further characterize the designed mixes. It was observed that the level of all toxic elements in both ECat and ZCat spent catalysts samples were within the acceptable limits. ECat mixes proved to be less susceptible to moisture damage compared to the ZCat mixes. For the amounts of catalyst used in this study, the ZCat mixes failed to meet the moisture resistance requirements of 80% retained strength and hence it is not recommended to be utilized as a filler material.

Effect of Compaction on the Aggregate Fracturing of Asphalt Concrete

Mon, 21 Dec 2015 14:58:00 GMT

Other states have elected not to adopt the 75 Blow Marshall Mix Design for their heavy traffic roads. Their reasons are that the 75 blow design cracks the larger aggregates. Therefore, a limited study was done during December, 1985, to try to determine what amount of cracking took place, and in what condition the cracks are in the mix.

Sulfur Extended Asphalt Laboratory Investigation--Mixture Characterization

Mon, 23 Nov 2015 16:46:12 GMT

This report provides a summary of a laboratory study on sulfur extended asphalt paving mixtures. The following major features were included in the study: (1) Design of laboratory experiment which included the use of mixtures which contained various amounts of sulfur, two viscosity levels of asphalt cement, and two types of aggregate (basalt and granite); (2) Evaluation of mixture design methods (Hveem and Marshall); (3) Determination of optimum binder contents; (4) Evaluation of mixture durability and aging characteristics; and (5) Development of revised mixture design criteria.

Application of Marshall Method in Hot Mix Design

Thu, 22 Oct 2015 18:03:57 GMT

This study found that, even though more research is needed in the correlation of laboratory mixing with pugmill mixing of hot mix asphalt, repeatability of results in using the Marshall Method can be improved by taking several precautionary measures. The results are highly affected by viscosity of the asphalt and the same condition is seen in pavements. The apparatus is simple, portable and inexpensive and the test method is very practical and rapid. Considering the conditions encountered in the field and necessity of quick measurements, the Marshall Method is certainly a very valuable tool in hot mix design and control.

Correlation of the Manual Compaction Hammer with Mechanical Hammers for the Marshall Method of Design for Asphaltic Concrete

Thu, 22 Oct 2015 18:03:57 GMT

The Mechanical Marshall Hammer Correlation Study is an attempt to correlate a new, more easily operated, mechanical hammer with the standard manual hammer presently in use. The new device is designated as hammer No. 2 and the older, hammer No. 1. Briquettes molded of pugmill mixes on three separate projects located in different areas of the State of Louisiana show that when varying the number of blows with hammer No. 2 from 75 to 105 on Projects II and III the density and Marshall stability did not reach the values obtained using 75 blows of the manual hammer. Bituminous mixtures were also molded in the laboratory using aggregates from six different sources. Five of these were gravel mixes and the other expanded clay aggregate. In addition to hammers 1 and 2, another mechanical hammer (No. 3) was introduced into the study. The only noticeable difference between the design of hammers No. 2 and 3 was that hammer No. 3 had an improved lift mechanism. In attempting to correlate these three hammers, results indicated that the manual hammer gave the highest density and Marshall stability. Between the two mechanical hammers, No. 3 was far superior to No. 2. It operated more efficiently and trouble-free and the results showed a closer correlation to those obtained using the manual hammer.

Modeling the Effect of Filler Materials on Performance of Hot Mix Asphalt Using Genetic Programming

Mon, 29 Jun 2015 15:52:09 GMT

This study aims to address the effect of filler materials (passing no. 200 sieve) on performance of hot mix asphalt mixtures. The Marshall mix design procedure was followed to prepare laboratory specimens using various types of filler materials to determine the optimum asphalt content. Furthermore, three different gradations with various amount of filler contents were selected to estimate the performance of asphalt mixture in laboratory conditions in terms of Marshall stability and flow. It was observed that more filler content increases the plasticity of the mix and thus the permanent deformation. Moreover, adding the hydrated lime as filler improves the functional properties of the asphalt mixtures. A nonlinear genetic programming algorithm was developed to predict and formulize the Marshall stability results using material characteristics. The prediction power of the employed soft computing technique is deemed satisfactory as compared to the experimental results.