Steam Curing of Portland Cement Concrete at Atmospheric Pressure, HR-40, 1962

The primary reason for using steam in the curing of concrete is to produce a high early strength. This high early strength is very desirable to the manufacturers of precast and prestressed concrete units, which often require expensive forms or stress beds. They want to remove the forms and move the units to storage yards as soon as possible. The minimum time between casting and moving the units is usually governed by the strength of the concrete. Steam curing accelerates the gain in strength at early ages, but the uncontrolled use of steam may seriously affect the growth in strength at later ages. The research described in this report was prompted by the need to establish realistic controls and specifications for the steam curing of pretensioned, prestressed concrete bridge beams and concrete culvert pipe manufactured in central plants. The complete project encompasses a series of laboratory and field investigations conducted over a period of approximately three years.

Floods of September 15-16, 1992, in the Thompson, Weldon, and Chariton River Basins, South-Central Iowa, HR-140, 1997

Water-surface-elevation profiles and peak discharges for the floods of September 15-16, 1992, in the Thompson, Weldon, and Chariton River Basins, south-central Iowa, are presented in this report. The profiles illustrate the 1992 floods along the Thompson, Weldon, Chariton, and South Fork Chariton Rivers and along Elk Creek in the south-central Iowa counties of Adair, Clarke, Decatur, Lucas, Madison, Ringgold, Union, and Wayne. Water-surface-elevation profiles for the floods of July 4, 1981, along the Chariton River in Lucas County and along the South Fork Chariton River in Wayne County also are included in the report for comparative purposes. The September 15-16, 1992, floods are the largest known peak discharges at gaging stations Thompson River at Davis City (station number 06898000) 57,000 cubic feet per second, Weldon River near Leon (station number 06898400) 76,200 cubic feet per second, Chariton River near Chariton (station number 06903400) 37,700 cubic feet per second, and South Fork Chariton River near Promise City (station number 06903700) 70,600 cubic feet per second. The peak discharges were, respectively, 1.7, 2.6, 1.4, and 2.1 times larger than calculated 100-year recurrence-interval discharges. The report provides information on flood stages and discharges and floodflow frequencies for streamflow-gaging stations in the Thompson, Weldon, and Chariton River Basins using flood information collected through 1995. Information on temporary bench marks and reference points established in the Thompson and Weldon River Basins during 1994-95, and in the Chariton River Basin during 1983-84 and 1994-95, also is included in the report. A flood history summarizes rainfall conditions and damages for floods that occurred during 1947, 1959, 1981, 1992, and 1993.

Feasibility Study of Dynamic Overload and Ultimate Load Tests of Full-Scale Highway Bridges, HR-160, 1973

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges are scheduled for removal. Five of these are old high-truss single-lane bridges, each bridge having several simple spans. The other bridge is a fairly modern (1955) double 4-span continuous beam-and-slab composite highway bridge. The availability of these bridges affords an unusual opportunity for study of the behavior of full-scale bridges. Because of the magnitude of the potential testing program, a feasibility study was initiated and the results are presented in this two-part final report. Part I summarizes the findings and Part II presents the supporting detailed information.

Ultimate Load Behavior of Full-Scale Highway Truss Bridges, Summary Report, HR-169, 1975

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges crossing the river were scheduled for removal. One of these, an old pin-connected, high-truss, single-lane bridge, was selected for a comprehensive testing program which included ultimate load tests, service load tests, and a supplementary test program. A second bridge was used for a limited service load test program. The results of the research are detailed in two interim reports. The first interim report outlines the ultimate load tests and the second interim report details the results of the service load and supplementary test program. This report presents a summary of these findings along with recommendations for implementation of the findings.

Maintenance of Pavement Skid Resistance (Open Graded Asphalt Friction Courses), Progress Report, HR-170, 1976

This project involved the evaluation of several aggregates previously rated poor to excellent with respect to skid resistance and certain mix design parameters. An open graded asphalt friction course was evaluated using 4 comparably graded aggregates: quartzite, fine grained limestone, coarse limestone and lightweight expanded shale. The performance investigations involved the verification of observations of the quartzite test sections, evaluation of the effect of blending the superior quartzite with a typical coarse grained-textured limestone, and the evaluation of the limestone. The effects of traffic on the aggregates used in the test sections were studied, as well as the relationship between asphalt content levels and traffic with respect to performance. The bond of the open graded friction course mixture was also evaluated. The SN performance of all test sections after sixteen months of exposure was found to be satisfactory in that none of the material combinations had polished to the point where unacceptable SN levels developed. When material combinations were compared, significant differences were noted.

Fatigue Behavior of Air-Entrained Concrete, HR-183, 1977

When a material fails under a number of repeated loads, each smaller than the ultimate static strength, a fatigue failure is said to have taken place. Many studies have been made to characterize the fatigue behavior of various engineering materials. The results of some of these studies have proved invaluable in the evaluation and prediction of the fatigue strength of structural materials. Considerable time and effort has gone into the evaluation of the fatigue behavior of metals. These early studies were motivated by practical considerations: The first fatigue tests were performed on materials that had been observed to fail after repeated loading of a magnitude less than that required for failure under the application of a single load. Mine-hoist chains, railway axles, and steam engine parts were among the first structural components to be recognized as exhibiting fatigue behavior. Since concrete is usually subjected to static loading rather than cyclic loading, need for knowledge of the fatigue behavior of concrete has lagged behind that of metals. One notable exception to this, however, is in the area of highway and airfield pavement design. Due to the fact that the fatigue behavior of concrete must be understood in the design of pavements and reinforced concrete bridges, highway engineers have provided the motivation for concrete fatigue studies since the 1920's.

Evaluation of Changes in Productivity Resulting from Removal of Soil for Highway Construction, HR-186, 1981

Borrow areas are created where soil is removed to provide needed fill material for highway and other construction projects. Where these areas are located beyond the highway right-of-way, they must be restored and returned to useful purposes. In Iowa, borrow areas are often developed on agricultural lands and therefore, it is necessary to return them to agricultural uses whenever possible. This research project was established to evaluate the changes in row crop productivity where borrow is removed for highway construction. Secondly, several reclamation techniques were selected to be applied to borrow area research sites and the response of crops to each treatment will be evaluated. All borrow area research sites were selected in 1977 from Iowa Department of Transportation construction plans. The Audubon and Buchanan County sites were completed in the fall of 1977 and May 1978, respectively. Both were used for research in 1978, 1979, and 1980. The two remaining sites in Hamilton and Lee Counties were completed in the fall of 1978 and research was conducted at these sites in 1979, 1980, and 1981. In this report, the 1981 results from the Hamilton and Lee County borrow sites will be presented. Secondly, a summary of the three years of research from each borrow area will be presented along with specific and general conclusions from the research project.

Dynamic Deflections for Determining Structural Rating of Flexible Pavements, HR-178, 1979

The Road Rater is a dynamic deflection measuring apparatus for flexible base pavements. The Road Rater replaces the Benkelman Beam which was last used by the Iowa DOT in 1977. Road Rater test results correlate reasonably well (correlation coefficient = 0.83) with Benkelman Beam test data. The basic differences between the Road Rater and Benkelman Beam are as follows: 1. The Benkelman Beam uses a static 18,000 lb. load while the Road Rater uses a dynamic 800 to 2,000 lb. loading. 2. The Road Rater tests much faster and more economically than the Benkelman Beam. 3. The Road Rater better simulates a moving truck than the Benkelman Beam. The basic operating principle of the Road Rater is to impart a dynamic loading and measure the resultant movement of the pavement with velocity sensors. This data, when properly adjusted for temperature by use of a nomograph included in this report, can be used to determine pavement life expectancy and estimate overlay thickness required. Road Rater testing will be conducted in the spring, when pavements are in their weakest condition, until seasonal correction factors can be developed. The Road Rater does not have sufficient ram weight to effectively evaluate load carrying capacity of rigid pavements. All rigid pavements react similarly to Road Rater testing and generally deflect from 0.65 to 1.30 mils. Research will be contined to evaluate rigid pavements with the Road Rater, however. The Road Rater has proven to be a reliable, troublefree pavement evaluation machine. The deflection apparatus was originally front-mounted,but was rear-mounted during the winter of 1977-78. Since that time, van handling has greatly improved, and front suspension parts are no longer overstressed due to improper weight distribution.

The Economic Potential of the Spergen Formation in Seven Southeastern Iowa Counties, HR-189, 1978

The middle Mississippian (Meramec Series) units include the Spergen Formation, the St. Louis Limestone and the Ste. Genevieve Formation which outcrop sporadically within a curvilinear subcrop band trending through southeastern and central Iowa. Studies of these units as they occur in Iowa have been cursory in the past, especially with regard to the lowermost occurring Meramecan unit, the Spergen Formation. The Spergen Formation, as it occurs in southeastern Iowa is being considered as a desirable concrete aggregate source. At present, the depth of occurrence, thickness variations and geographic extent are very poorly known and the nature of lithologic variation in Iowa is obscure. Due to a paucity of information of its thickness, extent and nature of rapid lateral facies variations, the full economic potential of the unit has not been realized in some areas of southeastern Iowa. This is especially disheartening in view of the decline of acceptable concrete aggregate source materials in southeastern Iowa. This report is an attempt to synthesize subsurface and surface data in order to present a more coherent picture of the depth, thickness and lithologic variations of the Spergen Formation. Recommendations have been made for the exploration of specific areas within the field area for future development of surface quarrying and subsurface mining operations where thickness, lithology and depth characteristics deem consideration. Due to the lack of adequate data points in some quadrants of the field area, some of the recommendations are drawn on rather tenuous grounds, but a concerted effort has been made to be conservative in these judgements.

A Computer Based Information System for County Equipment Cost Records, Final Report, HR-173, 1975

This appendix is divided into three sections. The first section contains abstracts of each of the eight computer programs in the system, instructions for keypunching the three input documents, and computer operating instructions pertaining to each program. The second section contains system flowcharts for the entire system as well as program flowcharts for each program. The last section contains PL/l program listings of each program.

Bonded, Thin-Lift, Non-Reinforced Portland Cement Concrete Resurfacing, HR-191, 1980

A Research Project involving two, three, four and five inches of bonded Portland Cement Concrete Overlay on a 1.3 mile Portland Cement Concrete pavement was conducted in Clayton County, Iowa, during September, 1977, centering on the following objectives: 1. Determine the mixing and proportioning procedures required in using a conventional, central mix proportioning plant to produce a dense Portland Cement Concrete mixture using standard mixes with super-water reducing admixtures; 2. Determine the economics, longevity and maintenance performance of a bonded, thin-lift, non-reinforced Portland Cement Concrete resurfacing course using conventional procedures, equipment and concrete paving mixtures both with and without super-water reducing admixtures; 3. Determine if an adequate bond between the existing pavement and an overlay of thin-lift, dense, non-reinforced Portland Cement Concrete can be obtained with only special surface cleaning and no surface removal or grinding.

Field Performance and Evaluation of Slurry Seals, HR-195, 1980

As part of the overall research program of evaluating asphalt emulsion slurry seal as a pavement maintenance material, 31 duplicate 500-ft test sections were constructed on U.S. 6 between Adel and Waukee in Dallas County during September and October of 1978. These test sections included combinations of eight aggregates, two gradings, three asphalt emulsions, two mineral fillers, and a range of emulsion contents determined by laboratory mix designs. The emulsion contents of the test sections varied from 10.3% for Section 7A (Ferguson coarse) to 32.9% for Section 31A (lightweight aggregate). The post-construction performance evaluation of the test sections, consisting primarily of the friction tests and surface appearance observations, was conducted at different time intervals up to 24 months after construction. At the 24-month final evaluation, most of the test sections had carried a total of 1.4 million vehicles.

Fatigue Behavior of Air-Entrained Concrete: Phase II, HR-197, 1979

When a material fails under a number of repeated loads, each smaller than the ultimate static strength, a fatigue failure is said to have taken place. Many studies have been made to characterize the fatigue behavior of various engineering materials. The results of some of these studies have proved invaluable in the evaluation and prediction of the fatigue strength of structural materials. Considerable time and effort have gone into the evaluation of the fatigue behavior of metals. These early studies were motivated by practical considerations: the first fatigue tests were performed on materials that had been observed to fail after repeated loading of a magnitude less than that required for failure under the application of a single load. Mine-hoist chains (1829), railway axles (1852), and steam engine parts were among the first structural components to be recognized as exhibiting fatigue behavior. Since concrete is usually subjected to static loading rather than cyclic loading, need for knowledge of the fatigue behavior of concrete has lagged behind that of metals. One notable exception to this, however, is in the area of highway and airfield pavement design. Due to the fact that the fatigue behavior of concrete must be understood in the design of pavements and reinforced concrete bridges, highway engineers have provided the motivation for concrete fatigue studies since the 1920s.

Evaluation of Fly Ash in Portland Cement Concrete Paving in Woodbury County, Iowa, Final Report, HR-201, 1980

The earliest overall comprehensive work on the use of fly ash in concrete was reported by Davis and Associates of the University of California in 1937. Since that time, there have been numerous applications of the use and varying propertions of fly ash in portland cement concrete mixes. Fly ash is a pozzolanic powdery by-product of the coal combustion process which is recovered from flue gases and is, generally associated with electric power generating plants. Environmental regulations enacted in recent years have required that fly ash be removed from the flue gases to maintain clean air standards. This has resulted in an increased volume of high quality fly ash that is considered a waste product or a by-product that can be utilized in products such as portland cement concrete. There are several sources of the high quality fly ash located in Iowa currently producing a combined total of 281,000 tons of material annually.

Evaluation of Control Structures for Stabilizing Degrading Stream Channels in Western Iowa, Phases II and III, HR-208A, 1985

Since the turn of the century, tributaries to the Missouri River in western Iowa have entrenched their channels to as much as six times their original depth. This channel degradation is accompanied by widening as the channel side slopes become unstable and landslides occur. The deepening and widening of these streams have endangered about 25% of the highway bridges in 13 counties [Lohnes et al. 1980]. Grade stabilization structures have been recommended as the most effective remedial measure for stream degradation [Brice et al., 1978]. In western Iowa, within the last seven years, reinforced concrete grade stabilization structures have cost between $300,000 and $1,200,000. Recognizing that the high cost of these structures may be prohibitive in many situations, the Iowa Department of Transportation (Iowa DOT) sponsored a study at Iowa State University (ISU) to find low-cost alternative structures. This was Phase I of the stream degradation study. Analytical and laboratory work led to the conclusion that alternative construction materials such as gabions and soil-cement might result in more economical structures [Lohnes et al. 1980]. The ISU study also recommended that six experimental structures be built and their performance evaluated. Phase II involved the design of the demonstration structures, and Phase III included monitoring and evaluating their performance.