Portland Cement Concrete Utilizing Recycled Pavement, MLR-77-3, 1977

Two objectives were involved in this recycling project: To determine if the asphalt concrete surfacing from an existing roadway could be removed, the existing portland cement concrete pavement broken, removed, crushed to 1-1/2 inch minus, proportioned through a conventional central mix proportioning plant with the addition of concrete sand, and placed with a conventional slipform paver; and to determine if a two course, composite pavement, each course of different mix proportions, could be placed monolithically with conventional slipform equipment after being proportioned and mixed in a conventional central mix plant. The project was completed with no major problem. The objectives were satisfactorily met. The project was a success to the degree that the Iowa D.O.T. is proceeding with at least two projects for the 1977 construction season that will utilize the old pavement as appregate for the new pavement.

Iowa D.O.T's Experience with Recycling Portland Cement Pavement and Asphalt Cement Pavement, MLR-77-4, 1977

This report provides details of IADOT's experience removing and crushing asphaltic concrete and portland cement concrete for recycling. The recycled material was used on interstate highways for the subbase and shoulders. The major problem IADOT encountered on this project was the removal of reinforcing steel from the broken concrete. The contractor used hydraulic powered shears to clip off all protruding steel during the removal and loading of the concrete on the grade. This project took place in 1977.

An Evaluation of Cover Aggregate Stripping Characteristics, Progress Report, HR-182, 1977

The increasing use of seal coats for surface restoration and the concurrent increase in failures of such treatments prompted the current research. Field observations indicated that certain aggregate types seemed to be more susceptible to failure, including stripping and disintegration. The research was thus designed to try to identify those aggregate types which would perform satisfactorily under normal conditions.

Recycling of Cass County I-80 Asphalt Concrete, Progress Report, HR-1011, 1977

Approximately 40,000 tons of slightly damaged asphalt concrete has been removed from Interstate 80 in Cass and stockpiled. Laboratory tests had indicated that this material had considerable value when upgraded with new aggregate and asphalt cement. This report documents the procedures used and results obtained on an experimental recycling project. It was demonstrated that present drum mixing-recycling equipment and procedures can be used to utilize this material with satisfactory results. Laboratory analyses of material components and mixtures were performed; these analyses indicate mixture can be produced that is uniform, stable, and very closely resembles mixture produced with all new material. Follow~up evaluations will be made to determine the effects of traffic and environment. Preliminary data indicate that plans should be made to incorporate the stockpiled material in projects near the stockpile site.

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.

Skid Resistance of the Secondary Road System in Iowa, MLR-77-1, 1977

The Iowa Department of Transportation has been conducting skid resistance tests on the paved secondary system on a routine basis since 1973. This report summarizes the data obtained through 1976 on 10,101 miles in 95 of the 99 counties in Iowa. A summary of the skid resistance on the secondary system is presented by pavement type and age. The data indicates that the overall skid resistance on this road system is excellent. Higher traffic roads (over 1000 vehicles per day) have a lower skid resistance than the average of the secondary roads for the same age and pavement type. The use of non-polishing aggregates in asphaltic concrete paving surface courses and transverse grooving of portland cement concrete paving on high traffic roads is recommended. The routine resurvey of skid resistance on the secondary road system on a 5-year interval is probably not economically justified and could be extended to a 10-year interval.

Adaptabilidade e estabilidade de cultivares de soja em cinco épocas de plantio no cerrado de Rondônia

Este trabalho teve o objetivo de avaliar o desempenho, a estabilidade e a adaptabilidade de 21 cultivares de soja (Glycine max (L.) Merrill), em cinco épocas de plantio no cerrado de Rondônia. O delineamento experimental foi blocos ao acaso, com três repetições. Os ensaios foram conduzidos no ano de 1996/97 pelo Centro de Pesquisa Agroflorestal de Rondônia, no Campo Experimental de Vilhena em Rondônia, RO. Os métodos utilizados apresentaram concordância entre os resultados alcançados, sendo que o comportamento das cultivares nas diferentes épocas de semeadura pode ser representado por um modelo linear. O coeficiente de resposta linear beta1i não apresentou diferença significativa (P<0,05) da unidade pelo teste t (beta1i = 1) em todas as cultivares testadas. As cultivares que apresentaram desvios de regressão sigma²(d i) significativos (P<0,05) foram MT/BR50 e EMBRAPA 31, com R² = 58,56% e 74,43%, respectivamente. As demais cultivares não apresentaram desvios de regressão significativos.

A guide to resources for the study of the recent history of the United States in the libraries of the University of Iowa, the State Historical Society of Iowa, and in the Herbert Hoover Presidential Library, 1977

This guide is designed as a finding aid for researchers seeking materials on a particular topic and it indicates the nature and extent of resources for the study of United States history available at the Historical Society of Iowa, the Herbert Hoover Presidential Library and the Iowa University Libraries.

Divergência genética entre cultivares de caupi

O objetivo deste trabalho foi quantificar a divergência genética de cultivares de caupi, agrupadas por análise multivariada visando à seleção de parentais superiores. Foram utilizadas 16 cultivares de caupi [Vigna unguiculata (L.) Walp.] do banco de germoplasma do Centro de Ciências Agrárias da Universidade Federal do Ceará. As observações fenotípicas foram realizadas num ensaio com delineamento experimental em blocos completos casualizados, com seis blocos e 16 tratamentos, incluindo três testemunhas, com parcela experimental de 24 m² e área útil de 16 m², sendo quatro fileiras de plantas, com espaços de 1,0 x 0,5 m, contendo duas plantas por cova. Para mensurar os caracteres fenotípicos, cinco plantas competitivas, localizadas nas duas fileiras centrais da parcela, foram tomadas ao acaso. Os cruzamentos entre os grupos I [TVx-337-3F e Vita-4 (TVu 1977-OD)] e II (Bengala e V-4 Alagoas) podem resultar em produção de novas combinações gênicas, por serem divergentes e reunirem maior número de caracteres agronomicamente desejáveis. Os caracteres que mais contribuem para divergência genética são o comprimento da vagem (36,80%) e o peso de 100 sementes (19,21%).

Atributos físicos de Latossolos adubados durante cinco anos com biossólido

A utilização do biossólido para fins agrícolas tem sido uma alternativa viável para resíduos de origem domiciliar e industrial. O objetivo deste trabalho foi avaliar o efeito da aplicação de biossólido nos atributos físicos de Latossolo Vermelho distrófico, textura média (LVd), e Latossolo Vermelho eutroférrico argiloso (LVef). Utilizaram-se as doses, acumuladas em 5 anos, de 0,0, 25,0, 47,5 e 50,0 Mg ha-1 de matéria seca de biossólido, incorporadas até 0,1 m com grade. As amostras deformadas foram coletadas no quinto ano, após a colheita do milho, nas camadas de 0,0-0,1, de 0,1-0,2 e de 0,2-0,3 m para determinação da composição granulométrica e matéria orgânica. As amostras indeformadas coletadas com cilindros metálicos de 0,030 m de altura e 0,048 m de diâmetro, também no quinto ano, foram utilizadas para determinação da densidade, porosidade e retenção de água no solo. A macroporosidade foi superior a partir de 47,5 Mg ha-1 e 50,0 Mg ha-1 de biossólido, no LVd e LVef, respectivamente, e a densidade do solo foi inferior na dose de 50,0 Mg ha-1 no LVd de textura média, na camada de 0,0-0,1 m. A aplicação de 50,0 Mg ha-1 de biossólido não alterou a porosidade total, a microporosidade e a retenção de água nos dois solos. O efeito da aplicação do biossólido depende do tipo de solo e da quantidade aplicada.

Geohydrology of Muscatine Island, Muscatine County, Iowa, 1977

The availability of large quantities of high-quality ground water from the Muscatine Island aquifer has had a tremendous impact upon urban, industrial and agricultural development of this part of Iowa. Although the nonpumping level of water has been lowered significantly near major pumping centers through time, proper management of this water resource can assure a continued supply of water for all competing users. This report provides basic information for long range management. Fold out maps are included.

Detection of Steel Corrosion in Bridge Decks and Reinforced Concrete Pavement, HR-156, 1977

The Iowa Department of Transportation initiated this research to evaluate the reliability, benefit and application of the corrosion detection device. Through field testing prior to repair projects and inspection at the time of repair, the device was shown to be reliable. With the reliability established, twelve additional devices were purchased so that this evaluation procedure could be used routinely on all repair projects. The corrosion detection device was established as a means for determining concrete removal for repair. Removal of the concrete down to the top reinforcing steel is required for all areas exhibiting electrical potentials greater than 0.45 Volt. It was determined that the corrosion detection device was not applicable to membrane testing. The corrosion detection device has been used to evaluate corrosion of reinforcing steel in continuously reinforced concrete pavement.

Prevention of Reflection Cracking in Asphalt Overlays with Structofors, Petromate, and Cerex, HR-158, 1977

This report presents construction methods and results using three reinforcing fabrics to prevent reflection cracking in an asphalt overlay. The original highway in the rural area was Portland Cement Concrete 20 feet wide. It was widened by adding 2 feet of asphaltic concrete 10 inches deep on each side prior to resurfacing. Data are presented for the widening joint and transverse cracks in the rural area and for the random cracking in the urban area.

Fibrous Concrete Resurfacing Greene County, Iowa, HR-165, 1977

The three miles of fibrous concrete resurfacing in Greene County, Iowa were placed in September and early October, 1973. It was recognized in advance that cracking and other performance characteristics of the fibrous concrete sections and of the control sections would be major factors in the evaluation of the project. A low level aerial survey was made of the old pavement. During construction of the resurfacing, the aerial survey was checked to insure that cracks in the old pavement were referenced to the 100 ft. station marks placed in the resurfacing. Crack surveys have been conducted on dates indicated below. Additional cracks found at each subsequent survey are shown in a color matching the date notation. April, 1974 November, 1974 October, 1975 October, 1976 October, 1977