Determination of Rumble Strip Effectiveness, HR-184, 1979

Rumble strips are patches of specially treated pavement surfaces which are designed to produce aural and tactile stimuli inside vehicles. The intent is to alert drivers and when desirable, cause them to slow down or come to a stop. Installations were made in a three-county area in Iowa to study rumble strip effectiveness as an accident reducing measure. The investigation of accidents at the various test sites showed that rumble strips were effective in reducing certain types of intersection accidents. Although no statistically significant effect of the saturation use was found on total accidents, there are indications that accidents may be reduced when used in low density i.e., rural type areas.

Wind Tunnel Analysis of the Effects of Planting at Highway Grade Separation Structures, HR-202, 1979

Blowing and drifting snow has been a problem for the highway maintenance engineer virtually since the inception of the automobile. In the early days, highway engineers were limited in their capability to design and construct drift free roadway cross sections, and the driving public tolerated the delays associated with snow storms. Modern technology, however, has long since provided the design expertise, financial resources, and construction capability for creating relatively snowdrift free highways, and the driver today has come to expect a highway facility that is free of snowdrifts, and if drifts develop they expect highway maintenance crews to open the highway within a short time. Highway administrators have responded to this charge for better control of snowdrifting. Modern highway designs in general provide an aerodynamic cross section that inhibits the deposition of snow on the roadway insofar as it is economically feasible to do so.

Transverse Joint Sealing with Various Sealants, Progress Report, HR-203, 1979

The objective of this research was to evaluate the performance of portland cement concrete pavement contraction joints utilizing a variety of sealants and joint preparations and to identify an effective sealant system. The variables evaluated were: (1) sealant material; (2) joint preparation; (3) size of saw cut (sealant reservoir); and (4) the use of backing material. This progress report contains project results to date.

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.

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.

A Further Evaluation of Concrete Bridge Deck Surfacing in Iowa, MLR-79-1, 1979

The Iowa Department of Transportation has overlaid 446 bridge decks with low slump dense concrete from 1964 through October 1978. The overall performance of these decks has been satisfactory. Nineteen bridges that were resurfaced with either low slump dense concrete (LSDC) or latex-modified concrete were analyzed for chloride content, electrical corrosion potential, delaminations or debonding, and deck surface condition. The resurfacing ages of these bridges range from 5 to 13 years. None of the bridges showed any evidence of surface distress and the chloride penetration into the resurfacing concrete is relatively low. There are delaminations in the original decks below the resurfacing on the majority of bridges examined. The delaminations are concluded to be caused by either (A) reinforcing steel corrosion, (B) not removing all delaminated concrete prior to placing the resurfacing concrete, or (C) creating an incipient fracture in the top surf ace of the original deck through the use of scarification equipment. The active corrosion of the reinforcing steel is predominately in the gutter line on the majority of bridges evaluated. Recommendations for future deck repairs include removal of concrete to the top layer of reinforcing steel in areas where an electrical corrosion potential of -0.35V or more is detected, providing more positive methods of locating delaminated concrete, and treating the curb and gutter line to reduce the potential damage from salt water.

Efeito do retardamento da secagem na qualidade fisiológica de sementes armazenadas de azevém anual

O objetivo deste trabalho foi avaliar os efeitos do retardamento da secagem e do armazenamento aberto na qualidade fisiológica de sementes de azevém anual (Lolium multiflorum Lam.), cultivar Comum-RS. Compararam-se períodos de retardamento da secagem (0, 2, 4, 6, 8, 12, 18, 24, 36 e 48 horas) e períodos de armazenamento (0, 4 e 8 meses). Enquanto submetidas aos períodos de retardamento da secagem, 24 kg de sementes ficaram acondicionadas em 18 caixas de poliestireno. A secagem foi realizada sobre piso de concreto, à sombra, por 12 horas, sendo completada em estufa a 35ºC com circulação forçada de ar. As sementes mantiveram o nível inicial de germinação durante os oito meses de armazenamento, mesmo com até 12 horas de retardamento da secagem; entretanto, com seis horas de retardamento, o vigor das sementes foi reduzido aos oito meses de armazenamento, mas se manteve praticamente inalterado aos quatro meses, com até 11 horas de retardamento. Sementes com germinação acima de 70% mantiveram este valor até oito meses de armazenamento, independentemente do período de retardamento da secagem.

Ganho genético decorrente da substituição anual de cultivares de milho

Cultivares de milho (Zea mays) são normalmente substituídas alguns anos após a indicação para cultivo. Os objetivos deste trabalho foram desenvolver e avaliar um teste de hipótese para determinar se as substituições anuais de cultivares, nos ensaios de competição de cultivares indicadas de milho, resultam em ganho genético para produtividade de grãos. Os ensaios de competição de cultivares de milho superprecoce, precoce e normal foram conduzidos nos anos agrícolas de 1998/1999, 1999/2000, 2000/2001 e 2001/2002. O delineamento experimental foi em blocos ao acaso, com três repetições. Cada parcela foi formada por duas fileiras de 5 m de comprimento, com espaçamento de 0,8 m. O ganho genético, quanto à produtividade de grãos, foi estimado pelo método proposto por Vencovsky et al., e a significância verificada pelo teste de hipótese proposto neste trabalho. As substituições anuais de cultivares de milho são dinâmicas e nem sempre resultam em ganho genético para produtividade de grãos.

Totes les vacances són diferents. És més beneficiós fer el descans anual sempre a la mateixa època i recordar-lo

Les vacances, el descans mensual, ens influeixen des del punt de vista psicològic i fisiològic, en vista de dos treballs científics recents que analitzen minuciosament els seus efectes.

Crack Survey for Fibrous P.C. Concrete Overlay Research in Greene County, Iowa, HR-165, 1979

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. A final report for research project HR-165, based upon overall performance evaluation was published in December 1978.

Asphalt Stabilization (Asphadur)/Reduction of Reflection Cracks (Monsanto Bidim Synthetic Fabric), HR-511, 1979

ASPHALT STABILIZATION (ASPHADUR): Asphadur (now called 3M Additive 5990) was incorporated into asphaltic concrete on a lane delineation, AC resurfacing, project in Council Bluffs. The experimental feature was included in the eastbound lanes of Interstate 480, beginning at the bridge over the Missouri River and ending at the bridge over North 41st Street. The project was constructed in October 1979. The objective of the project was to investigate the manufacturer's claims of improved strength, stability and durability of an asphalt mix. REDUCTION OF REFLECTION CRACKS (MONSANTO BIDIM SYNTHETIC FABRIC): A lane delineation project was constructed in the eastbound lanes of Interstate 480 in Council Bluffs. A synthetic fabric, Monsanto Bidim C-28, was placed between the portland cement concrete and two inches of Type A asphaltic concrete resurfacing containing Asphadur. The experimental feature began at the bridge over the Missouri River and ended at the bridge over North 41st Street. The project was constructed in October 1979. The objective of this experimental project was to determine the effectiveness of the fabric in reducing reflective cracking in an asphaltic concrete overlay.

Survey of D.O.T.'s Traffic Paint Costs in 1979, HR-515, 1980

This report presents the results of a survey on the use of yellow versus white traffic paint. It was found that in most states the white paint was less expensive than the yellow. A substantial savings could be realized if an all white traffic marking system was permitted by the Federal Highway Administration. Paint costs from each state are presented, as well as by each region.

Erosividade mensal e anual da chuva no Estado de Minas Gerais

Este trabalho objetivou estimar e mapear a erosividade média (EI30) mensal e anual, analisar a distribuição espacial da precipitação, durante o período chuvoso, e identificar zonas similares quanto a EI30 no Estado de Minas Gerais. Foram levantadas séries históricas de precipitação diária de 248 estações climatológicas para estimativa do coeficiente de chuva de Fournier (Rc). Baseado na relação EI30 x Rc, verificada em algumas localidades do Estado, o índice EI30 mensal foi estimado para as 248 estações. A geoestatística foi aplicada no mapeamento dos dados. O Estado de Minas Gerais pôde ser dividido em três zonas, com erosividade anual variando de 5.000 a 12.000 MJ mm ha-1 ano-1 : erosividade média-alta, nas regiões central, nordeste e parte da Zona da Mata; alta, no Triângulo Mineiro (extremo da região), e parte do nordeste e sul do Estado; e muito alta, na maior parte do Triângulo Mineiro, Alto Paranaíba, noroeste e leste. A erosividade não apresentou relação com a latitude e longitude e foi influenciada por efeitos orográficos e características climáticas de cada região.

Field Evaluation of Pavement Marking Materials, MLR-79-02, 1979

Pavement marking materials other than conventional paint must be evaluated as environmental standards become more restrictive. The new EPA classification for solvents states that all oil paints are photochemically reactive and, therefore, contribute to smog. This will eventually result in the elimination of organic solvents from all paints, which may occur in Iowa by 1985. The Special Investigations Section of the Office of Materials field reviewed all urban and rural applications of pavement marking materials in the spring of 1979. The field review consisted of a visual estimation of percent marking missing, percent satisfactory, and percent non-satisfactory; reflective readings by ERMA; and notation of special conditions which may have impacted performance. ERMA was not effective in evaluating the reflective quality of pavement marking materials. No pavement marking materials evaluated have been successful enough to date to totally replace conventional painting methods.

Penetration Characteristics of Asphalt in a Recycled Mixture, MLR-79-03, 1979

Samples of both recycled and nonrecycled asphaltic concrete were extracted in increments by the Abson Recovery Method and the penetration of the asphalt from each increment determined. The recycled projects were plantsite operations containing various amounts of virgin gravel. Cored samples were taken from the pavements on Kossuth County roads that were constructed as recycled projects in 1975, 1976, and 1977. Cored samples were also taken from a Kossuth County paving project done in 1975, that was not recycled. Comparison mix samples from 1978 construction projects in Marshall and Woodbury Counties of non - recycled projects are included. The test data from the penetrations of the recovered asphalt indicates that mixing of the old and new asphalt occurs very extensively in the hot recycling process. In laboratory controlled conditions it is difficult to coat aggregates with different penetration asphalts and prevent them from mixing.