Recycled Asphalt Pavement Kossuth County Iowa, HR-176, 1982

In 1975, Kossuth County had 492 miles of asphalt pavements, sixty percent of which were between l5 and 20 years old. Many of these roadways were in need of rehabilitation. Normally, asphaltic resurfacing would be the procedure for correcting the pavement deterioration. There are areas within the state of Iowa which do not have Class I aggregate readily available for asphalt cement concrete paving. Kossuth County is one of those areas. The problem is typified by this project. Limestone aggregate to be incorporated into the asphalt resurfacing had to be hauled 53 miles from the quarry to the plant site. The cost of hauling good quality aggregate coupled with the increasing cost of asphalt cement encouraged Kossuth County to investigate the possibility of asphaltic pavement recycling. Another problem, possibly unique to Kossuth County, was the way the original roadways had been constructed. A good clay soil was present under 3 to 4 feet of poorer soil. In order to obtain this good clay soil for subbase construction, the roadway ditches were excavated 1 to 3 feet into the clay soil layer. The resultant roadway tops were several feet above the surrounding farm land and generally less than 26 feet wide. To bring the existing roadway up to current minimum design width, there were two choices: One was to widen the roadway by truck hauling soil and constructing new 4 to 6 foot shoulders. The cost of widening by this method averaged $36,000 per mile in 1975. The other choice was to remove the old pavement and widen the roadway by lowering the grade line. The desire to provide wider paved roadways gave Kossuth County the additional incentive needed to proceed with a pavement recycling project.

Development of Quality Standards for Inclusion of High Recycled Asphalt Pavement Content in Asphalt Mixtures – Phase II, TR-658, 2015

To conserve natural resources and energy, the amount of recycled asphalt pavement has been steadily increasing in the construction of asphalt pavements. The objective of this study is to develop quality standards for inclusion of high RAP content. To determine if the higher percentage of RAP materials can be used on Iowa’s state highways, three test sections with target amounts of RAP materials of 30%, 35% and 40% by weight were constructed on Highway 6 in Iowa City. To meet Superpave mix design requirements for mixtures with high RAP contents, it was necessary to fractionate the RAP materials. Three test sections with actual RAP materials of 30.0%, 35.5% and 39.2% by weight were constructed and the average field densities from the cores were measured as 95.3%, 94.0%, and 94.3%, respectively. Field mixtures were compacted in the laboratory to evaluate moisture sensitivity using a Hamburg Wheel Tracking Device. After 20,000 passes, rut depths were less than 3mm for mixtures obtained from three test sections. The binder was extracted from the field mixtures from each test section and tested to identify the effects of RAP materials on the performance grade of the virgin binder. Based on Dynamic Shear Rheometer and Bending Beam Rheometer tests, the virgin binders (PG 64-28) from test sections with 30.0%, 35.5% and 39.2% RAP materials were stiffened to PG 76-22, PG 76-16, and PG 82-16, respectively. The Semi-Circular Bending (SCB) test was performed on laboratory compacted field mixtures with RAP amounts of 30.0%, 35.5% and 39.2% at two different temperatures of -18 and -30 °C. As the test temperature decreased, the fracture energy decreased and the stiffness increased. As the RAP amount increased, the stiffness increased and the fracture energy decreased. Finally, a condition survey of the test sections was conducted to evaluate their short-term pavement performance and the reflective transverse cracking did not increase as RAP amount was increased from 30.0% to 39.2%.

Development of Quality Standards for Inclusion of High Recycled Asphalt Pavement Content in Asphalt Mixtures, TR-624, 2012

The main objective of this research is to examine the effects that different methods of RAP stockpile fractionation would have on the volumetric mix design properties for high-RAP content surface mixes, with the goal of meeting all specified criteria for standard HMA mix designs. To determine the distribution of fine aggregates and binder in RAP stockpile, RAP materials were divided by each sieve size. The composition of RAP materials retained on each sieve was analyzed to determine the optimum fractionation method. Fractionation methods were designed to separate the stockpile at a specified sieve size to control the amount of fine RAP materials which contain higher amounts of fine aggregates and dust contents. These fine RAP materials were used in reduced proportions or completely eliminated, thereby decreasing the amount of fine aggregate materials introduced to the mix. Mix designs were performed using RAP materials from four different stockpiles and the two fractionated methods were used with high-RAP contents up to 50% by virgin binder replacement. By using a fractionation method, a mix with up to 50% RAP was successfully designed while meeting all Superpave criteria and asphalt film thickness requirement by controlling the dust content from RAP stockpiles.

THE PERFORMANCE AND MODIFICATION OF RECYCLED ELECTRONIC WASTE PLASTICS FOR THE IMPROVEMENT OF ASPHALT PAVEMENT MATERIALS

Bulk electric waste plastics were recycled and reduced in size into plastic chips before pulverization or cryogenic grinding into powders. Two major types of electronic waste plastics were used in this investigation: acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS). This research investigation utilized two approaches for incorporating electronic waste plastics into asphalt pavement materials. The first approach was blending and integrating recycled and processed electronic waste powders directly into asphalt mixtures and binders; and the second approach was to chemically treat recycled and processed electronic waste powders with hydro-peroxide before blending into asphalt mixtures and binders. The chemical treatment of electronic waste (e-waste) powders was intended to strengthen molecular bonding between e-waste plastics and asphalt binders for improved low and high temperature performance. Superpave asphalt binder and mixture testing techniques were conducted to determine the rheological and mechanical performance of the e-waste modified asphalt binders and mixtures. This investigation included a limited emissions-performance assessment to compare electronic waste modified asphalt pavement mixture emissions using SimaPro and performance using MEPDG software. Carbon dioxide emissions for e-waste modified pavement mixtures were compared with conventional asphalt pavement mixtures using SimaPro. MEPDG analysis was used to determine rutting potential between the various e-waste modified pavement mixtures and the control asphalt mixture. The results from this investigation showed the following: treating the electronic waste plastics delayed the onset of tertiary flow for electronic waste mixtures, electronic waste mixtures showed some improvement in dynamic modulus results at low temperatures versus the control mixture, and tensile strength ratio values for treated e-waste asphalt mixtures were improved versus the control mixture.

Recycled asphalt mixtures produced with high percentage of different waste materials

The use of sustainable solutions in construction is not just an option, but is increasingly becoming a need of the Society. Thus, nowadays the recycling of waste materials is a growing technology that needs to be continuously improved, namely by researching new solutions for waste valorisation and by increasing the amount of wastes reused. In the paving industry, the reuse of reclaimed asphalt (RA) is becoming common practice, but needs further research work. Thus, this study aims to increase the incorporation of RA and other waste materials in the production of recycled asphalt mixtures in order to improve their mechanical, environmental and economic performance. Recycled mixtures with 50% RA were analysed in this study, including: i) RA selection, preparation and characterization; ii) incorporation of other waste materials as binder additives or modifiers, like used motor oil (UMO) and waste high density polyethylene (HDPE); iii) production of different mixtures (without additives; with UMO; with UMO and HDPE) and comparison of their performance in order to assess the main advantages of each solution. With this study it was concluded that up to 7.5 % of UMO and 4.0 % of HDPE can be used in a new modified binder for asphalt mixtures with 50 % of RA, which have excellent properties concerning the rutting with WTS = 0.02 mm/103 cycles, the fatigue resistance with ε6 = 160.4, and water sensitivity with an ITSR of 81.9 %.

Evauation of Recycled Asphalt Concrete Pavements: Final Report for Kossuth County, Iowa, HR-1888, February 1980

After some success with a small asphalt pavement recycling project in 1975, Kossuth County, Iowa programmed a much larger undertaking during the 1976 construction season. The work performed in 1975 indicated that a quality product could be produced with some modifications to conventional equipment. As anticipated , the major problem encountered was the excessive air pollution created during the heating and mixing process. As part of its 1976 road program, Kossuth County developed plans for recycling sixteen miles of existing asphalt pavements using the "hot mix" recycling process. One project, ten miles in length, was selected by the Federal Highway Authority as part of "Demonstration Project No. 39, Recycling Asphalt Pavements." The FHWA provided a $29,500 grant t o the project to be used for project testing and evaluation. Cooperation and input into the work proposed for 1976 was received from many sources. The people and organizations contributing were the Federal Highway Authority, the Iowa Department of Environmental Quality, the Federal Environmental Protection Agency, several contractors, and personnel from the Kossuth County Engineer's Office.

Review of Cold In-Place Recycled Asphalt Concrete Projects, HR-392, 1998

Highway Research Project HR-392 was undertaken to evaluate cold in-place asphalt recycled (CIR) projects in the State of Iowa. The research involved assessment of performance levels, investigation of factors that most influence pavement performance and economy, and development of guidelines for CIR project selection. The performance was evaluated in two ways: Pavement Condition Indices (PCI, U.S. Corps of Engineers) were calculated and overall ratings were given on ride and appearance. A regression analysis was extrapolated to predict the future service life of CIR roads. The results were that CIR roads within the State of Iowa, with less than 2000 annual average daily traffic (AADT), have an average predicted service life of fifteen to twenty-six years. Subgrade stability problems can prevent a CIR project from being successfully constructed. A series of Dynamic Cone Penetrometer (DCP) tests were conducted on a CIR project that experienced varying levels of subgrade failure during construction. Based on this case study, and supporting data, it was determined that the DCP test can be used to evaluate subgrades that have insufficient stability for recycling. Overall, CIR roads in Iowa are performing well. It appears that the development of transverse cracking has been retarded and little rutting has occurred. Contracting agencies must pay special attention to the subgrade conditions during project selection. Because of its performance, CIR is a recommended method to be considered for rehabilitating aged low volume (<2000 AADT) asphalt concrete roads in Iowa.

Evaluation of Air Pollution Control Devices for Asphalt Pavement Recycling Operations, HR-188, Progress Report, 1977

This report discusses the asphalt pavement recycling project designated Project HR-188 in Kossuth County, Iowa. Specific objectives were: (a) to determine the effectiveness of drum mixing plant modifications designed to control air pollution within limits specified by the Iowa Department of Environmental Quality; (b) to assess the impact of varying the proportions of recycled and virgin aggregates, (c) to assess the impact of varying the production rate of the plant, and (d) to assess the impact of varying the mixing temperature. The discussion includes information on the proposed use of research funds, project location and description, the project planning conference, plan development, bid letting, asphalt plant configuration, actual plant operation, why this method is successful, probable process limitations, pollution results, recycled pavement test results, and the cost of virgin vs. recycled asphalt pavements.

Recycled asphalt mixtures with foamed bitumen: an alternative to build ecofriendly road pavements

Nowadays, recycling has become a very important objective for the society in the scope of a closed loop product life cycle. In recent years, new recycling techniques have been developed in the area of road pavements that allow the incorporation of high percentages of reclaimed asphalt (RA) materials in recycled asphalt mixtures. The use of foamed bitumen for production of recycled asphalt mixtures is one of those techniques, which also allows the reduction of the mixing temperatures (warm mix technology). However, it is important to evaluate if this solution can maintain or improve the performance of the resulting mixtures. Thus, the main aim of the present study is to assess the performance of warm recycled asphalt mixtures incorporating foamed bitumen as the new binder and 50% RA, in comparison with a control mixture using conventional bitumen. Four mixtures have been produced with 50% RA, one of them at typical high mixing temperatures with a conventional bitumen (control mixture) and the other three with foamed bitumen at different production temperatures. These four mixtures were tested to evaluate their compactability and water sensitivity. The laboratory test results showed that the production of recycled mixtures with foamed bitumen can be reduced by 40ºC without changing the performance of the resulting mixtures.

Investigation of Warm-Mix Asphalt Using Iowa Aggregates Final Report, April 2011

The implementation of warm-mix asphalt (WMA) is becoming more widespread with a growing number of contractors utilizing various WMA technologies. Early research suggests WMA may be more susceptible to moisture damage than traditional hot-mix asphalt (HMA) mixes. The objectives of this study are to test the binder and mix properties of WMA technologies for both field- and laboratory-produced mixes to determine the performance of WMA compared to traditional HMA. Field- and laboratory-produced mixes were studied. The laboratory-produced mixes compared HMA control mixes with WMA mixes that had the same mix design. The WMA technologies used for the laboratory study were Advera, Sasobit, and Evotherm. The field study tested four WMA field-produced mixes. Each of the four mixes had a corresponding control HMA mix. The WMA technologies used in the field study included: Evotherm 3G/Revix, Sasobit, and Double Barrel Green Foaming. The three main factors for this study were WMA/HMA, moisture-conditioned/not moisture-conditioned, and reheated/not reheated. Mixes were evaluated based on performance tests. Binder testing was performed to determine the rheological differences between HMA and WMA binders to determine if binder grade requirements change with the addition of WMA additives. The conclusions of this study are as follows:  Reduced mixing and compaction temperatures were achieved.  Statistical differences were found when comparing tensile strength ratio (TSR) values for both laboratory- and field-produced mixes. In the laboratory, none of the WMA additives performed as well as the HMA. For the field mixes, all TSR values passed Iowa’s minimum specification of 0.8 but, on average, WMA is lower compared to HMA TSR values.  Dynamic modulus results show that, on average, HMA will have higher dynamic modulus values. This means the HMA exhibits stiffer material properties compared to WMA; this may not necessarily mean superior performance in all cases.  Flow number results show that WMA has reduced flow number values compared to HMA. The only exception was the fourth field mix and weather delayed production of the control mix by nine days. The laboratory mixes showed that flow number values increased significantly with the addition of recycled asphalt pavement (RAP).  In the laboratory study, Advera reduced TSR values. Given that Advera is a foaming agent, the increase in moisture susceptibility is likely attributed to the release of water necessary for the improvement of the workability of the asphalt mixture.

Improvement of Longitudinal Joints in Asphalt Pavement, HR-215, 1987

Research is reported which attempted to identify construction procedures that will provide an improved centerline joint on asphalt concrete pavements. Various construction procedures and their evaluation are described. Core densities were made and visual inspections were made 3 years after construction. Center cracking was measured at 4, 5, and 6 years. The only procedure to rank the same when comparing cracking and density (delete the 1:1 slope shoe on the edge) is described. This procedure had the highest average density and also the least cracking through 1985. This method provided the best performance for 4 years after construction and involved the removal of the 1:1 slope shoe from the paver when placing the surface course. This method had 9.0% cracked after 4 years and 100% cracked after 6 years of service.

Polymerized Asphalt Cement, HR-533, 1989

In 1986, a 0.34 mile experimental section of polymerized asphalt cement (PAC30) concrete was placed in the westbound driving lane of Interstate 80 in western Iowa. It was used in a 2" asphalt concrete inlay using 20% recycled asphalt pavement. The virgin aggregate included 41% crushed gravel, 25% crushed quartzite and 14% natural sand. The evaluation of the project was severely limited when a 1987 reconstruction project extended into the experimental section leaving only 395 feet. Rut depths under a 4-foot gage were taken for a period of two years. No significant rutting occurred in the experimental polymerized section. The frequency of transverse cracking in the polymerized AC section was the same as that of the comparative AC-20 section. The asphalt paving mixture made with polymerized AC cost 120% of the cost of the conventional mix.

Recycled Asphalt Pavements - Kossuth County Iowa, HR-176, 1975

Kossuth County is located in North Central Iowa bordering on the State of Minnesota. It is the largest county in Iowa consisting of 28 congressional townships. The population of the county is 23,000 of which 11,000 people live in the rural area. There are 13 towns located in the county with the county seat, Algona, being the largest with a population of 6,100. Major industry of the area is grain farming with some beef and hog production. Naturally, where there is good grain farm land it follows that there is poor soil available for road construction and pavements. However, below the 3 to 4 feet of good farm land of Kossuth there is present a good grade of clay soil which does make an adequate base for surfacing when placed and compacted on top of the roadbed. As early as 1950, the then Kossuth County Engineer, H.M. Smith, embarked on a program of stage construction in building new grades and pavements. The goal of his program was primarily to conserve the county's rapidly dwindling supply of surfacing materials, and also, to realize the side effects of providing smooth and dustless roads for the public. Engineer Smith was fully aware of the poor soils that existed for road construction, but he also knew about the good clay that lay below the farm soil. Consequently, in his grading program he insisted that road ditches be dug deep enough to allow the good clay soil to be compacted on top of the roadbed. The presence of the compacted clay on top of the road resulted in a briding affect over the farm soil. The stage construction program satisfied the objectives of aggregate construction and dust control but did generate other problems which we are now trying to solve as economically as possible.

Transverse Cracking Study of Asphalt Pavement, HR-1020, 1981

At a pavement management study meeting in Omaha, Nebraska, September 12 and 13, 1979, the states of Iowa, Kansas and Nebraska agreed on the need for an in-depth engineering study of thermal cracking of bituminous pavement. In addition, the states of Oklahoma and North Dakota agreed to participate in the study. The scope of the study was to analyze all functions relating to the thermal cracking problem to determine how different uses of preventative materials, mix design measures, maintenance repairs, and design of bituminous pavements and overlays might be contributing to the problem and to determine what improvements might be made in these procedures to reduce the problem of thermal cracking. This publication describes the study and its conclusions. One of the conclusions is that the study did not address what the authors believe to be the major contributor to transverse cracking - the subgrade and subbase.