Low-Cost Rural Surface Alternatives: Literature Review and Recommendations, TR-632, 2013

Freezing and thawing action induces damage to unbound gravel roads in Iowa resulting in maintenance costs for secondary road departments. Some approaches currently used by County Engineers to deal with this problem include temporarily spreading rock on the affected areas, lowering or improving drainage ditches, tiling, bridging the area with stone and geosynthetic covered by a top course of aggregate or gravel, coring boreholes and filling them with calcium chloride to melt lenses and provide drainage, and re-grading the crown to a slope of 4% to 6% to maximize spring drainage. However, most of these maintenance solutions are aimed at dealing with conditions after they occur. This study was tasked with identifying alternative approaches in the literature to mitigate the problem. An annotated bibliographic record of literature on the topic of frost-heave and thaw-weakening of gravel roads was generated and organized by topic, and all documents were assessed in terms of a suitable rating for mitigating the problem in Iowa. Over 300 technical articles were collected and selected down to about 150 relevant articles for a full assessment. The documents collected have been organized in an electronic database, which can be used as a tool by practitioners to search for information regarding the various repair and mitigation solutions, measurement technologies, and experiences that have been documented by selected domestic and international researchers and practitioners. Out of the 150+ articles, 71 articles were ranked as highly applicable to conditions in Iowa. The primary mitigation methods identified in this study included chemical and mechanical stabilization; scarification, blending, and recompaction; removal and replacement; separation, and reinforcement; geogrids and cellular confinement; drainage control and capillary barriers, and use of alternative materials. It is recommended that demonstration research projects be established to examine a range of construction methods and materials for treating granular surfaced roadways to mitigate frost-heave and thaw-weakening problems. Preliminary frost-susceptibility test results from ASTM D5916 are included for a range of Iowa materials.

Statewide Economic Impacts of Disaster-Related Payments to Support Household and Private and Public Sector Recovery in Iowa, January 2010

There have been a multitude of programs providing assistance to the state of Iowa in the past 18 months. Springtime 2008 disasters resulted in tornado damage and widespread flood damage to large fractions of the state. In consequence, there was a very large flow of federal and state resources dedicated to assisting community and statewide recovery efforts. The nation was in recession as well and continued to be in recession through much of 2009. A sizeable amount of assistance found its way to Iowa under the American Recovery and Reinvestment Act of 2009 in the forms of infrastructure stimulus spending, income supports and other safety net spending for households, and stabilization assistance for essential public services like education. On top of that, the state of Iowa authorized the I Jobs program as an additional infrastructure development program, and as a jobs stimulus program. The total amount of spending for all types of programs, disaster or economic recovery related, is perhaps as high as $7.5 billion over the next few years.

Hwyneeds: Methodology, Analysis and Evaluation, March 2001

The quadrennial need study was developed to assist in identifying county highway financial needs (construction, rehabilitation, maintenance, and administration) and in the distribution of the road use tax fund (RUTF) among the counties in the state. During the period since the need study was first conducted using HWYNEEDS software, between 1982 and 1998, there have been large fluctuations in the level of funds distributed to individual counties. A recent study performed by Jim Cable (HR-363, 1993), found that one of the major factors affecting the volatility in the level of fluctuations is the quality of the pavement condition data collected and the accuracy of these data. In 1998, the Center for Transportation Research and Education researchers (Maze and Smadi) completed a project to study the feasibility of using automated pavement condition data collected for the Iowa Pavement Management Program (IPMP) for the paved county roads to be used in the HWYNEEDS software (TR-418). The automated condition data are objective and also more current since they are collected in a two year cycle compared to the 10-year cycle used by HWYNEEDS right now. The study proved the use of the automated condition data in HWYNEEDS would be feasible and beneficial in educing fluctuations when applied to a pilot study area. In another recommendation from TR-418, the researchers recommended a full analysis and investigation of HWYNEEDS methodology and parameters (for more information on the project, please review the TR-418 project report). The study reported in this document builds on the previous study on using the automated condition data in HWYNEEDS and covers the analysis and investigation of the HWYNEEDS computer program methodology and parameters. The underlying hypothesis for this study is thatalong with the IPMP automated condition data, some changes need to be made to HWYNEEDS parameters to accommodate the use of the new data, which will stabilize the process of allocating resources and reduce fluctuations from one quadrennial need study to another. Another objective of this research is to investigate the gravel roads needs and study the feasibility of developing a more objective approach to determining needs on the counties gravel road network. This study identifies new procedures by which the HWYNEEDS computer program is used to conduct the quadrennial needs study on paved roads. Also, a new procedure will be developed to determine gravel roads needs outside of the HWYNEED program. Recommendations are identified for the new procedures and also in terms of making changes to the current quadrennial need study. Future research areas are also identified.

The Effects of Crushed Particles in Asphalt Mixtures, HR-311 and MLR-88-16, 1990

One of the most serious impediments to the continued successful use of hot-mix asphalt (HMA) pavements is rutting. The Iowa Department of Transportation has required 85% crushed particles and 75-blow Marshall mix design in an effort to prevent rutting on Interstate roadways. Relationships between the percent of crushed particles and resistance to rutting in pavement through the use of various laboratory test procedures must be developed. HMA mixtures were made with 0, 30, 60, 85, and 100% crushed gravel, crushed limestone, and crushed quartzite combined with uncrushed sand and gravel. These aggregate combinations were used with 4, 5, and 6% asphalt cement (ac). Laboratory tests included Marshall stability, resilient modulus, indirect tensile, and creep. A creep resistance factor (CRF) was developed to provide a single numeric value for creep test results. The CRF values relate well to the amount of crushed particles and the perceived resistance to rutting. The indirect tensile test is highly dependent on the ac with a small effect from the percent of crushed particles. The Marshall stability from 75-blow compaction relates well to the percent of crushed particles. The resilient modulus in some cases is highly affected by grade of ac.

The Effects of Crushed Particles in Asphalt Mixtures, HR-311 and MLR-88-16, Part 1, 1990

One of the most serious impediments to the continued successful use of hot mix asphalt (HMA) pavements is rutting. The Iowa Department of Transportation has required 85% crushed particles and 75 blow Marshall mix design in an effort to prevent rutting on interstate roadways. The objective of this research and report is to develop relation~hips between the percent of crushed particles and resistance to rutting in pavement through the use of various laboratory test procedures. HMA mixtures were made with 0, 30, 60, 85 and 100% crushed gravel, crushed limestone and crushed quartzite combined with uncrushed sand and gravel. These aggregate combinations were used with 4, 5 and 6% asphalt cement (ac). Laboratory testing included Marshall stability, resilient modulus, indirect tensile and creep. A creep resistance factor (CRF) was developed to provide a single numeric value for creep test results. The CRF values relate well to the amount of crushed particles and the perceived resistance to rutting. The indirect tensile test is highly dependent on the ac with a small effect from the percent of crushed particles. The Marshall stability from 75 blow compaction relates well to the percent of crushed particles. The resilient modulus in some cases is highly affected by grade of ac.

Relating Creep Testing to Rutting of Asphalt Concrete Mixes, HR-311, Part 2, 1991

The Iowa Department of Transportation began creep and resilient modulus testing of asphalt concrete mixtures in 1989. Part 1 of this research reported in January 1990 was a laboratory study of hot mix asphalt (HMA) mixtures made with O, 30, 60, 85 and 100% crushed gravel, crushed limestone and crushed quartzite combined with uncrushed sand and gravel. Creep test results from Marshall specimens related well to the percent of crushed particles and the perceived resistance to rutting. The objective of this research, part 2, was to determine if there was a meaningful correlation between pavement rut depth and the resilient modulus or the creep resistance factor. Four and six inch diameter cores were drilled from rutted primary and interstate pavements and interstate pavements with design changes intended to resist rutting. The top 2 1/2 inches of each core, most of which was surface course, was used for creep and resilient modulus testing. There is a good correlation between the resilient modulus of four and six inch diameter cores. Creep resistance factors of four and six inch diameter cores also correlated well. There is a poor correlation between resilient modulus and the creep resistance factor. The rut depth per million 18,000 pound equivalent single axle loadings (ESAL) for these pavements did not correlate well with either the resilient modulus or the creep resistance factor.

Identification of Practices, Design, Construction, and Repair Using Trenchless Technology, TR-570, 2010

Trenchless technologies are methods used for the construction and rehabilitation of underground utility pipes. These methods are growing increasingly popular due to their versatility and their potential to lower project costs. However, the use of trenchless technologies in Iowa and their effects on surrounding soil and nearby structures has not been adequately documented. Surveys of and interviews with professionals working in trenchless-related industries in Iowa were conducted, and the results were analyzed and compared to survey results from the United States as a whole. The surveys focused on method familiarity, pavement distress observed, reliability of trenchless methods, and future improvements. Results indicate that the frequency of pavement distress or other trenchless-related issues are an ongoing problem in the industry. Inadequate soil information and quality control/quality assurance (QC/QA) are partially to blame. Fieldwork involving the observation of trenchless construction projects was undertaken with the purpose of documenting current practices and applications of trenchless technology in the United States and Iowa. Field tests were performed in which push-in pressure cells were used to measure the soil stresses induced by trenchless construction methods. A program of laboratory soil testing was carried out in conjunction with the field testing. Soil testing showed that the installations were made in sandy clay or well-graded sand with silt and gravel. Pipes were installed primarily using horizontal directional drilling with pipe diameters from 3 to 12 inches. Pressure cell monitoring was conducted during the following construction phases: pilot bore, pre-reaming, and combined pipe pulling and reaming. The greatest increase in lateral earth pressure was 5.6 psi and was detected 2.1 feet from the centerline of the bore during a pilot hole operation in sandy lean clay. Measurements from 1.0 to 2.5 psi were common. Comparisons were made between field measurements and analytical and finite element calculation methods.

Fly Ash Soil Stabilization for Non-Uniform Subgrade Soils, Volume I: Engineering Properties and Construction Guidelines, TR-461, 2005

Soil treated with self-cementing fly ash is increasingly being used in Iowa to stabilize fine-grained pavement subgrades, but without a complete understanding of the short- and long-term behavior. To develop a broader understanding of fly ash engineering properties, mixtures of five different soil types, ranging from ML to CH, and several different fly ash sources (including hydrated and conditioned fly ashes) were evaluated. Results show that soil compaction characteristics, compressive strength, wet/dry durability, freeze/thaw durability, hydration characteristics, rate of strength gain, and plasticity characteristics are all affected by the addition of fly ash. Specifically, Iowa selfcementing fly ashes are effective at stabilizing fine-grained Iowa soils for earthwork and paving operations; fly ash increases compacted dry density and reduces the optimum moisture content; strength gain in soil-fly ash mixtures depends on cure time and temperature, compaction energy, and compaction delay; sulfur contents can form expansive minerals in soil–fly ash mixtures, which severely reduces the long-term strength and durability; fly ash increases the California bearing ratio of fine-grained soil–fly ash effectively dries wet soils and provides an initial rapid strength gain; fly ash decreases swell potential of expansive soils; soil-fly ash mixtures cured below freezing temperatures and then soaked in water are highly susceptible to slaking and strength loss; soil stabilized with fly ash exhibits increased freeze-thaw durability; soil strength can be increased with the addition of hydrated fly ash and conditioned fly ash, but at higher rates and not as effectively as self-cementing fly ash. Based on the results of this study, three proposed specifications were developed for the use of self-cementing fly ash, hydrated fly ash, and conditioned fly ash. The specifications describe laboratory evaluation, field placement, moisture conditioning, compaction, quality control testing procedures, and basis of payment.

Iowa Interstate Rest Area Stabilization Ponds, September 1979

This report is presented in two parts . P a r t I takes a new look at the design of rest area stabilization ponds after nearly 10 years' experience with some of the existing ponds and in the light of new design standards issued by Iowa DEQ. The Iowa DOT is embarking on improvements t o the ponds a t some of the r e s t areas. These improvements may include installation of drainage tile around the ponds to lower the water table below the pond bottom, sealing of the ponds with bentonite clay to reduce the infiltration to limits recently established by Iowa DEQ, and the enlargement of the ponds installation of aeration equipment t o increase the pond capacity. As the Iowa DOT embarks on this improvement program, it behooves them t o make only the improvements that are absolutely necessary to achieve waste water treatment goals. These ponds are subject to an extremely seasonal load and thus the ordinary standards used for pond design are not appropriate. Thus, Part I of the report presents a rationale for design and operation of the ponds which is deemed appropriate for t h e i r unique seasonally loaded character. Part I1 of the report looks a t the feasibility of using wind power for the aeration of the ponds, if and when aeration is deemed necessary.

Development of LRFD Procedures for Bridge Pile Foundations in Iowa: Volume II: Field Testing of Steel Piles in Clay, Sand, and Mixed Soils and Data Analysis, September 2011

In response to the mandate on Load and Resistance Factor Design (LRFD) implementations by the Federal Highway Administration (FHWA) on all new bridge projects initiated after October 1, 2007, the Iowa Highway Research Board (IHRB) sponsored these research projects to develop regional LRFD recommendations. The LRFD development was performed using the Iowa Department of Transportation (DOT) Pile Load Test database (PILOT). To increase the data points for LRFD development, develop LRFD recommendations for dynamic methods, and validate the results ofLRFD calibration, 10 full-scale field tests on the most commonly used steel H-piles (e.g., HP 10 x 42) were conducted throughout Iowa. Detailed in situ soil investigations were carried out, push-in pressure cells were installed, and laboratory soil tests were performed. Pile responses during driving, at the end of driving (EOD), and at re-strikes were monitored using the Pile Driving Analyzer (PDA), following with the CAse Pile Wave Analysis Program (CAPWAP) analysis. The hammer blow counts were recorded for Wave Equation Analysis Program (WEAP) and dynamic formulas. Static load tests (SLTs) were performed and the pile capacities were determined based on the Davisson’s criteria. The extensive experimental research studies generated important data for analytical and computational investigations. The SLT measured loaddisplacements were compared with the simulated results obtained using a model of the TZPILE program and using the modified borehole shear test method. Two analytical pile setup quantification methods, in terms of soil properties, were developed and validated. A new calibration procedure was developed to incorporate pile setup into LRFD.

Stream Stabilization in Western Iowa: Structure Evaluation and Design Manual, HR-385, 1998

Stream degradation is the action of deepening the stream bed and widening the banks due to the increasing velocity of water flow. Degradation is pervasive in channeled streams found within the deep to moderately deep loess regions of the central United States. Of all the streams, however, the most severe and widespread entrenchment occurs in western Iowa streams that are tributaries to the Missouri River. In September 1995 the Iowa Department of Transportation awarded a grant to Golden Hills Resource Conservation and Development, Inc. The purpose of the grant, HR-385 "Stream Stabilization in Western Iowa: Structure Evaluation and Design Manual", was to provide an assessment of the effectiveness and costs of various stabilization structures in controlling erosion on channeled streams. A review of literature, a survey of professionals, field observations and an analysis of the data recorded on fifty-two selected structures led to the conclusions presented in the project's publication, Design Manual, Streambed Degradation and Streambank Widening in Western Iowa. Technical standards and specifications for the design and construction of stream channel stabilization structures are included in the manual. Additional information on non-structural measures, monitoring and evaluation of structures, various permit requirements and further resources are also included. Findings of the research project and use and applications of the Design Manual were presented at two workshops in the Loess Hills region. Participants in these workshops included county engineers, private contractors, state and federal agency personnel, elected officials and others. The Design Manual continues to be available through Golden Hills Resource Conservation and Development.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. II, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. While in the past extensive research has been conducted on slope stability investigations and analysis, this current research study consists of field investigations addressing both the characterization and reinforcement of such slope failures. While Volume I summarizes the research methods and findings of this study, Volume II provides procedural details for incorporating an infrequently-used testing technique, borehole shear tests, into practice. Fifteen slopes along Iowa highways were investigated, including thirteen slides (failed slopes), one unfailed slope, and one proposed embankment slope (the Sugar Creek Project). The slopes are mainly comprised of either clay shale or glacial till, and are generally gentle and of small scale, with slope angle ranging from 11 deg to 23 deg and height ranging from 6 to 23 m. Extensive field investigations and laboratory tests were performed for each slope. Field investigations included survey of slope geometry, borehole drilling, soil sampling, in-situ Borehole Shear Testing (BST) and ground water table measurement. Laboratory investigations mainly comprised of ring shear tests, soil basic property tests (grain size analysis and Atterberg limits test), mineralogy analyses, soil classifications, and natural water contents and density measurements on the representative soil samples from each slope. Extensive direct shear tests and a few triaxial compression tests and unconfined compression tests were also performed on undisturbed soil samples for the Sugar Creek Project. Based on the results of field and lab investigations, slope stability analysis was performed on each of the slopes to determine the possible factors resulting in the slope failures or to evaluate the potential slope instabilities using limit equilibrium methods. Deterministic slope analyses were performed for all the slopes. Probabilistic slope analysis and sensitivity study were also performed for the slope of the Sugar Creek Project. Results indicate that while the in-situ test rapidly provides effective shear strength parameters of soils, some training may be required for effective and appropriate use of the BST. Also, it is primarily intended to test cohesive soils and can produce erroneous results in gravelly soils. Additionally, the quality of boreholes affects test results, and disturbance to borehole walls should be minimized before test performance. A final limitation of widespread borehole shear testing may be its limited availability, as only about four to six test devices are currently being used in Iowa. Based on the data gathered in the field testing, reinforcement investigations are continued in Volume III.

Clay Mineralogy of a Gumbotil, HR-106, 1964

Investigation of the clay minerals in a gumbotil associated with the Mahaska soil series in Keokuk County, Iowa, indicates that the principal clay mineral is a dioctahedral calcium montmorillonite. Other clay minerals present in this gumbotil are kaolinite and mica, although they are in much smaller percentages. The investigation also pointed out difficulties involved in analyzing this type of soil by standard X-ray procedures and the complications introduced in the analysis of soil samples with high iron content utilizing standard accepted diffraction techniques.

Treating Iowa's Marginal Aggregates and Soils by Foamix Process, HR-212, 1980

Quality granular materials suitable for building all-weather roads are not uniformly distributed throughout the state of Iowa. For this reason the Iowa Highway Research Board has sponsored a number of research programs for the purpose of developing new and effective methods for making use of whatever materials are locally available. This need is ever more pressing today due to the decreasing availability of road funds and quality materials, and the increasing costs of energy and all types of binder materials. In the 1950s, Professor L. H. Csanyi of Iowa State University had demonstrated both in the laboratory and in the field, in Iowa and in a number of foreign countries, the effectiveness of preparing low cost mixes by stabilizing ungraded local aggregates such as gravel, sand and loess with asphalt cements using the foamed asphalt process. In this process controlled foam was produced by introducing saturated steam at about 40 psi into heated asphalt cement at about 25 psi through a specially designed and properly adjusted nozzle. The reduced viscosity and the increased volume and surface energy in the foamed asphalt allowed intimate coating and mixing of cold, wet aggregates or soils. Through the use of asphalt cements in a foamed state, materials normally considered unsuitable could be used in the preparation of mixes for stabilized bases and surfaces for low traffic road construction. By attaching the desired number of foam nozzles, the foamed asphalt can be used in conjunction with any type of mixing plant, either stationary or mobile, batch or continuous, central plant or in-place soil stabilization.

Pilot Construction Project for Granular Shoulder Stabilization, TR-634, 2013

Granular shoulders need to be maintained on a regular basis because edge ruts and potholes develop, posing a safety hazard to motorists. The successful mitigation of edge-rut issues for granular shoulders would increase safety and reduce the number of procedures currently required to maintain granular shoulders in Iowa. In addition, better performance of granular shoulders reduces the urgency to pave granular shoulders. Delaying or permanently avoiding paving shoulders where possible allows more flexibility in making investments in the road network. To stabilize shoulders and reduce the number of maintenance cycles necessary per season, one possible stabilizing agent—acidulated soybean oil soapstock—was investigated in this research. A pilot testing project was conducted for selected problematic shoulders in northern and northeastern Iowa. Soapstock was applied on granular shoulders and monitored during application and pre- and post-application. Application techniques were documented and the percentage of application success was calculated for each treated shoulder section. As a result of this research, it was concluded that soybean oil soapstock can be an effective stabilizer for granular shoulders under certain conditions. The researchers also developed draft specifications that could possibly be used to engage a contractor to perform the work using a maintenance-type construction contract. The documented application techniques from this project could be used as guidance for those who want to apply soapstock for stabilizing granular shoulders but might not be familiar with this technique.