A Different Perspective for Investigation of PCC Pavement Deterioration, HR-2074, 1995

Portland Cement Concrete (PCC) pavement has served the State of Iowa well for many years. The oldest Iowa pavement was placed in LeMars in 1904. Beginning in 1931, many miles of PCC pavement were built to "get out of the mud". Many of these early pavements provided good performance without deterioration for more than 50 years. In the late 1950s, Iowa was faced with severe PCC pavement deterioration called D cracking. Research identified the cause of this deterioration as crushed limestone containing a bad pore system. Selective quarrying and ledge control has alleviated this problem. In 1990, cracking deterioration was identified on a three-year-old pavement on US 20 in central Iowa. The coarse aggregate was a crushed limestone with an excellent history of performance in PCC pavement. Examination of cores showed very few cracks through the coarse aggregate particles. The cracks were predominately confined to the matrix. The deterioration was identified as alkali-silica reactivity (ASR) by a consultant. To investigate the cause of the deterioration, the Iowa DOT and Iowa State University jointly purchased a high resolution, low vacuum Hitachi Scanning Electron Microscope (SEM) with an energy dispersion detector. Subsequent evaluation identified no concentration of silica gel (silicon-Si), but did identify substantial amounts of sulfur-S and aluminum-AL (assumed to be ettringite) in the air voids. Some of these voids have cracks radiating from them leading us to conclude that the ettringite filled voids were a center of pressure causing the crack. The ettringite in the voids, after being subjected to sodium chloride (NaCl), initially swells and then dissolves. This low vacuum SEM research of PCC pavement deterioration supports the following conclusions: (1) A low vacuum SEM and an energy dispersion detector are very important for proper evaluation of PCC pavement deterioration; (2) There are instances today where PCC pavement deterioration is mistakenly identified as ASR; (3) Ettringite initially expands when subjected to NaCl; and the ettringite filled voids are a center-of-pressure that cracks the PCC; and (4) The deterioration of some current premature PCC pavement distress locations is caused by factors related to the formation of excessive ettringite.

Variations of Tine Texturing of PCC Pavement, MLR-93-4, 1996

Seven experimental texture sections were constructed on the Polk-Jasper RP-163-1(50)--16--77 project just east of Des Moines. The experimental sections included two groove depths for a longitudinal tine texture and 13 mm (1/2 in.), 19 mm (1 in.) and variable spaced transverse tine textures. An artificial turf textured section was also included. Friction values and a rating of objectionable noise were determined for all sections. All transverse tine textures generated a high level of objectionable noise. The longitudinal tine texture was rated very good in regard to objectionable noise. At this time, all tined textures are providing satisfactory friction values.

Avaliação espectral de solos desenvolvidos em uma toposseqüência de diabásio e folhelho da região de Piracicaba, SP

Este trabalho teve como objetivo estudar as alterações de solosdesenvolvidos numa toposseqüência composta por diabásio e folhelho (Piracicaba, SP), e sua relação com os dados espectrais. Ocorrem na toposseqüência os solos Latossolo Roxo (LR), Latossolo Vermelho-Escuro (LE), Podzólico Vermelho-Escuro (PE), Litossolo (Li) e Aluvial (Al) dos quais foram coletadas amostras a três profundidades. Foram obtidos dados de reflectância bidirecional dessas amostras em laboratório com espectrorradiômetro na faixa de 350 a 2.500 nm. As alterações da reflectância das amostras de solo das camadas superficiais e subsuperficiais foram relacionadas às diferenças nos teores de matéria orgânica e argila, que foram parâmetros importantes na caracterização espectral dos solos. Ao longo da toposseqüência, ocorreram alterações nas características dos solos, principalmente nos teores de ferro e silte e na mineralogia, que influenciaram nos dados espectrais. Os solos desenvolvidos de diabásio apresentaram altos teores de ferro, o que refletiu em concavidades mais acentuadas nas curvas espectrais em 850 nm, e intensidades de reflectância menores, ao contrário dos solos desenvolvidos de folhelho. A reflectância do PE apresentou-se mais intensa do que o LR e LE. Os solos menos intemperizados Li e Al apresentaram intensidades de reflectância mais elevadas que os mais intemperizados, LR e LE.

Influência da idade da muda de Eucalyptus grandis no desenvolvimento da lagarta-rosca Nomophila sp.

O objetivo deste trabalho foi estudar a influência da idade das mudas de Eucalyptus grandis (Myrtaceae) no desenvolvimento da lagarta-rosca Nomophila sp. (Lepidoptera: Pyralidae). Esse inseto foi alimentado em laboratório (24±2°C, 80±15% de UR e fotofase de 12 horas) com folhas de eucalipto com 20-30 dias ou com 50-60 dias de idade. Os parâmetros observados foram: número, duração e caracterização dos estádios, largura da cápsula cefálica, comprimento do corpo, duração da fase larval, relação entre número de estádios e o sexo, viabilidade e comportamento das lagartas de Nomophila sp. Esse inseto mostrou melhor desenvolvimento em todos os parâmetros observados, em mudas de eucalipto com 20-30 dias do que em mudas com 50-60 dias de idade, quando o caule está mais enrijecido. Isto reforça a necessidade de se realizar uma adubação balanceada nas mudas de E. grandis, como forma de acelerar seu desenvolvimento, e torná-las morfologicamente menos favoráveis ao desenvolvimento das lagartas de Nomophila sp.

Características edafoclimáticas e informações socioeconômicas no diagnóstico de agroecossistemas da região de São Carlos, SP

O planejamento regional de agroecossistemas é um componente fundamental para a sustentabilidade da atividade agrícola, devendo considerar a realidade biofísica e socioeconômica. A agropecuária cumpre importante papel na região de São Carlos, SP, porém esta localiza-se em grande parte numa área de preservação ambiental. Este trabalho visou delimitar a Zona Agroecológica dessa região e diagnosticar seus agroecossistemas por meio de informações edafoclimáticas e socioeconômicas. A delimitação foi baseada no clima, geomorfologia e divisão administrativa. Da área delimitada estudou-se o clima, pedologia, uso da terra, estrutura fundiária e o manejo dos agroecossistemas. A Zona delimitada ocupa 286.824,08 ha, e é composta pelos municípios de Analândia, Itirapina, Santa Maria da Serra, São Carlos, São Pedro e Torrinha. Há potencial para a atividade agrícola, ocorrendo principalmente solos arenosos e de baixa fertilidade. Pastagens e cana-de-açúcar são os usos predominantes; a distribuição da posse da terra é desigual, e existe risco de degradação ambiental, pois não se empregam práticas compatíveis com as características naturais. Recomenda-se o uso de práticas que maximizem a conservação do solo, sua correção, e o aproveitamento de seus nutrientes, assim como o cultivo de espécies adaptadas a solos arenosos, que sejam pouco exigentes em fertilidade e resistentes a estresse hídrico.

The clc element of Pseudomonas sp. strain B13, a genomic island with various catabolic properties.

Pseudomonas sp. strain B13 is a bacterium known to degrade chloroaromatic compounds. The properties to use 3- and 4-chlorocatechol are determined by a self-transferable DNA element, the clc element, which normally resides at two locations in the cell's chromosome. Here we report the complete nucleotide sequence of the clc element, demonstrating the unique catabolic properties while showing its relatedness to genomic islands and integrative and conjugative elements rather than to other known catabolic plasmids. As far as catabolic functions, the clc element harbored, in addition to the genes for chlorocatechol degradation, a complete functional operon for 2-aminophenol degradation and genes for a putative aromatic compound transport protein and for a multicomponent aromatic ring dioxygenase similar to anthranilate hydroxylase. The genes for catabolic functions were inducible under various conditions, suggesting a network of catabolic pathway induction. For about half of the open reading frames (ORFs) on the clc element, no clear functional prediction could be given, although some indications were found for functions that were similar to plasmid conjugation. The region in which these ORFs were situated displayed a high overall conservation of nucleotide sequence and gene order to genomic regions in other recently completed bacterial genomes or to other genomic islands. Most notably, except for two discrete regions, the clc element was almost 100% identical over the whole length to a chromosomal region in Burkholderia xenovorans LB400. This indicates the dynamic evolution of this type of element and the continued transition between elements with a more pathogenic character and those with catabolic properties.

Relação entre a estrutura foliar de feijoeiro e a pré-infecção por Glomerella cingulata f.sp. phaseoli

Os objetivos deste trabalho foram mensurar a área da nervura secundária e quantificar o número de tricomas da superfície foliar de cultivares de feijoeiro suscetível (Carioca), moderadamente resistente (Pérola) e resistente (IAPAR-81) à antracnose, e observar as relações entre tais características com o estágio pré-infeccional. Para mensurar a área da nervura secundária, fragmentos foliares foram amostrados, fixados em FAA 50, conservados em álcool 70%, infiltrados em resina glicol-metacrilato, cortados transversalmente e corados com azul de toluidina. Os tricomas foram quantificados em impressões epidérmicas em microscópio de projeção. Na análise pré-infeccional, o material foi fixado em glutaraldeído 2,5% e processado para o estudo ao microscópio eletrônico de varredura. A cultivar resistente apresentou menor área de nervura secundária e maior pilosidade que a cultivar moderadamente resistente e a suscetível. Na cultivar resistente, por causa da menor área de nervura e maior pilosidade, o patógeno permaneceu sobre a nervura e envolvido com o tricoma. Na cultivar suscetível, com maior área de nervura e menor pilosidade, foram observadas necrose e estruturas fúngicas na superfície foliar. Há relação entre estas características foliares e a resistência à antracnose durante o estágio pré-infeccional do patógeno.

Desenvolvimento de larvas de Steindachneridion sp. em diferentes condições de refúgio e luminosidade

Avaliou-se a influência da luminosidade e do uso de refúgios no desenvolvimento inicial de larvas de surubim do Iguaçu (Steindachneridion sp. Garavello) (Siluriforme: Pimelodidae). Utilizaram-se 1.000 larvas com peso e comprimento inicial de 62,2 mg e 18,02 mm, respectivamente, distribuídas em 20 aquários de 35 L, durante 22 dias. Os tratamentos consistiram dos ambientes: escuro sem refúgio, claro com refúgio artificial, escuro com refúgio artificial, claro com refúgio natural e claro sem refúgio, com quatro repetições cada, distribuídos em delineamento inteiramente casualizado. As larvas receberam a mesma alimentação em todos os tratamentos. As melhores taxas de sobrevivência foram verificadas nos ambientes: escuro sem refúgio, claro com refúgio natural e claro sem refúgio, com 84, 76 e 70%, respectivamente. O melhor desenvolvimento das larvas ocorreu em ambiente escuro e sem refúgio. O tratamento escuro com refúgio artificial apresentou diferenças significativas em relação à sobrevivência e ao peso final dos outros tratamentos, com grande heterogeneidade quanto ao peso. Ambientes escuros e sem refúgios são os mais adequados para o desenvolvimento inicial de larvas de surubim do Iguaçu.

Image Analysis of PCC and AC Pavements Using SEM Images, HR-346, 1994

The major objective of this work was to evaluate the potential of image analysis for characterizing air voids in Portland cement Concrete (PCC), voids and constituents of Asphalt Concrete (AC) and aggregate gradation in AC. Images for analysis were obtained from a scanning electron microscope (SEM). Sample preparation techniques are presented that enhance signal differences so that backscattered electron (BSE) imaging, which is sensitive to atomic number changes, can be effectively employed. Work with PCC and AC pavement core samples has shown that the low vacuum scanning electron microscope (LVSEM) is better suited towards rapid analyses. The conventional high vacuum SEM can also be used for AC and PCC analyses but some distortion within the sample matrix will occur. Images with improved resolution can be obtained from scanning electron microscope (SEM) backscatter electron (BSE) micrographs. In a BSE image, voids filled with barium sulfate/resin yield excellent contrast in both PCC and AC. There is a good correlation between percent of air by image analysis and linear traverse.

Evaluation of Maturity and Pulse Velocity Measurements for PCC Traffic Opening Decisions, HR-380, 1998

Concrete paving is often at a disadvantage in terms of pavement type selection due to the time of curing required prior to opening the pavement to traffic. The State of Iowa has been able to reduce traffic delay constraints through material selection and construction methods to date. Methods for monitoring concrete strength gain and quality have not changed since the first concrete pavements were constructed in Iowa. In 1995, Lee County and the Iowa DOT cooperated in a research project, HR-380, to construct a 7.1 mile (11. 43 km) project to evaluate the use of maturity and pulse velocity nondestructive testing (NDT) methods in the estimation of concrete strength gain. The research identified the pros and cons of each method and suggested an instructional memorandum to utilize maturity measurements to meet traffic delay demands. Maturity was used to reduce the traffic delay opening time from 5-7 days to less than 2 days through the implementation of maturity measurements and special traffic control measures. Recommendations on the development of the maturity curve for each project and the location and monitoring of the maturity thermocouples are included. Examples of equipment that could easily be used by project personnel to estimate the concrete strength using the maturity methods is described.

Longitudinal Joint Forming in PCC Pavements, MLR-00-05, Construction Report, 2003

In conventional construction practices, a longitudinal joint is sawed in a PCC (Portland Cement Concrete) pavement to control concrete shrinkage cracking between two lanes of traffic. Sawing a joint in hardened concrete is an expensive and time consuming operation. The longitudinal joint is not a working joint (in comparison to a transverse joint) as it is typically tied with a tie bar at 30 inch spacing. The open joint reservoir, left by the saw blade, typically is filled or sealed with a durable crack sealant to keep incompressibles and water from getting into the joint reservoir. An experimental joint forming knife has been developed. It is installed under the paving machine to form the longitudinal joint in the wet concrete as a part of the paving process. Through this research method, forming a very narrow longitudinal joint during the paving process, two conventional paving operations can be eliminated. Joint forming eliminates the need of the joint sawing operation in the hard concrete, and as the joint that is formed does not leave a wide-open reservoir, but only a hairline crack, it does not need the joint filling or sealing operation. Therefore, the two conventional longitudinal joint sawing and sealing operations are both being eliminated by this innovation. A laboratory scale prototype joint forming knife was built and tested, initially forming joints in small concrete beams. The results were positive so the method was proposed for field testing. Initial field tests were done in the construction season of 2001, limited to one paving contractor. A number of modifications were made to the knife throughout the field tests. About 3000 feet of longitudinal joint was formed in 2001. Additional testing was done in the 2002 construction season, working with the same contractor. About 150,000 feet of longitudinal joint was formed in 2002. Evaluations of the formed joints were done to determine longitudinal joint hairline crack development rate and appearance. Additional tests will be done in the next construction season to improve or perfect the longitudinal joint forming technique.

Air Content and Permeability of PCC Pavements: 1909 to 2006, MLR-05-02, 2007

Portland cement concrete pavements have given excellent service history for Iowa. Many of these pavements placed during the 1920’s and 1930’s are still in service today. Many factors go in to achieve a long term durable concrete pavement. Probably the most important is the durability of the aggregate. Until the 1930’s, pit run gravel was the most predominant aggregate used. Many of these gravels provided long term performance and their durability is dependent upon the carbonate fraction of the gravel. Later, limestone (calcium carbonate) and dolomite (calcium, magnesium carbonate) sources were mined across Iowa. The durability of these carbonate aggregates is largely dependent upon the pore system which can cause freeze thaw problems known as D-cracking, which was a problem with some sources during the 1960’s. Also, some of these carbonate aggregates are also susceptible to deterioration from deicing salts. Geologists have identified the major components that affect the durability of these carbonate aggregates and sources are tested to ensure long term performance in Portland cement concrete. Air entrainment was originally put in concrete to improve scaling resistance. It is well known that air entrainment is required to provide freeze thaw protection in concrete pavements today. In Iowa, air entrainment was not introduced in concrete pavements until 1952. This research investigates properties that made older concrete pavements durable without air entrainment.