Laboratory Evaluation of Roller-Compacted Concrete, MLR-86-6, 1988

Fine limestone aggregate is abundant in several areas of the state. The aggregate is a by-product from the production of concrete stone. Roller compacted concrete (RCC) is a portland cement concrete mixture that can be produced with small size aggregate. The objective of the research was to evaluate limestone screenings in RCC mixes. Acceptable strength and freeze/thaw durability were obtained with 300 pounds of portland cement and 260 pounds of Class C fly ash. The amount of aggregate passing the number 200 sieve ranged from 4.6 to 11 percent. Field experience in Iowa indicates that the aggregate gradation is more critical to placeability and compactibility than laboratory strength and durability.

Drying Shrinkage in P.C. Concrete, MLR-89-5, 1990

Crack formation has been a problem on some recently constructed bridges in Iowa. Drying shrinkage has been considered a contributing factor in that cracking. The study was undertaken to evaluate some of those material properties that contribute to the magnitude of drying shrinkage. Cement content, cement composition, fly ash and retarding admixture were the factors studied. Concrete prisms were cast for seven mixes and, after curing, were exposed to 100 deg F heat at ambient humidity for 280 days. The following were observed from the testing: (1) Higher C3A content cement concrete produced larger shrinkage; (2) Use of fly ash increased shrinkage; (3) Use of retarder increased shrinkage; and (4) Lowering the cement content reduced the shrinkage.

Freeze-Thaw Durability of Concretes with Infilling of Ettringite in Voids, Phase 2, MLR-94-9, 1997

Examination of field portland cement concrete cores, from Iowa pavements with premature deterioration, reveals extensive infilling of calcium sulfate aluminum (CSA) compound in their air voids. A previous study (Phase I) has shown some evidence of the correlation between freeze-thaw durability of concretes and ettringite infilling. To further verify the previous observation, a more extensive experimental program was conducted in this Phase 2 study. A total of 101 concrete mixes were examined. Seven cements, six fly ashes, two water reducers and three coarse aggregates were used in the concrete mixes. Specimens were under moist curing for up to 223 days before being subjected to the freeze-thaw cycling. An environmental treatment consisting of three consecutive wet [70 deg F (21 deg C) in distilled water]/dry [120 deg F (49 deg C) in oven] cycles was applied to some specimens. Immediately prior to the freeze-thaw cycling, most specimens were examined by a low-vacuum scanning electron microscope (SEM) for their microstructure. The results obtained further demonstrate the correlation between concrete freeze-thaw response and CSA compound infilling in the air voids. The extent of the infilling depends on the period of moist curing as well as the wet/dry treatment. The extent of the infilling also relates to materials used. Concrete mixes with extensive infilling are more vulnerable to the freeze-thaw attack. Based on the obtained results, material criteria on cements and fly ashes for mainline paving were proposed for minimizing potential infilling of CSA compound in concrete.

Evaluation of Rapid Determination of the Chloride Permeability of Portland Cement Concrete by AASHTO T277-83, MLR-86-11, 1987

An Iowa D.O.T. Laboratory built machine was constructed for the chloride permeability testing of concrete by measuring electric current through a specimen between a salt solution and a base solution. This study had two purposes. The first was to evaluate the machine's performance. To do this, three concrete mixes were made consisting of different cement factors and water/cement ratios. Each mix was tested for chloride ion content by the 90- day salt ponding method and for chloride permeability at a 28-day cure by the permeability machine. The results from each test were evaluated to see if there was correlation between chloride ion content and the chloride permeability. It was determined that there was a correlation and that the permeability machine was satisfactory for determining chloride permeability in concrete. The second purpose of this study was to examine the effects that pozzolans have on the chloride permeability of concrete. Four mixes were made: one without any pozzolans as a control, one with class C fly ash, one with class F fly ash, and one with silica fume. Specimens from each mix were evaluated for chloride ion content by the 90-day salt ponding test and by the laboratory built machine for chloride permeability after curing 28 days. Specimens from these mixes were also taken from the salt ponding slabs after completion of the ponding test to examine the effect chloride ion content has on the operation of the chloride permeability machine. Specimens containing pozzolans were also examined for chloride permeability after a cure of 180 days. It was determined that the addition of pozzolans to concrete lowers the chloride permeability as measured by the permeability machine. Class F fly ash and silica fume in the concrete had a major effect in lowering the chloride permeability in concrete as measured by the permeability machine.

Fine Sand for Use in PC Concrete, MLR-88-6, 1989

In several locations of Iowa, it is becoming more difficult to produce concrete sand consistently at a reasonable cost. Both ASTM and AASHTO have specifications for concrete sands that allow a finer, poorer graded sand than Iowa specifications. The objective of the study was to develop standard mix designs to permit the use of finer graded sand for PC concrete. Three hundred cylinders were made from five sands available in the state. Based on the results of the study, the following are recommended: (1) Create another class of concrete sand by: (a) lowering the current mortar strength ratio from 1.5 to 1.3, (b) raising the allowance for the percent passing one sieve and retained on the next from 40 to 45, and (c) including a provision that 25 to 60 percent passing the number 30 sieve is required for the sand; and (2) Modify the standard paving mixes with and without fly ash for use with the finer sand as follows: (a) 8% more cement and fly ash for B-2 to B-5 mixes, (b) 7% more cement and fly ash for A-2 to A-5 mixes, and (c) 5% more cement and fly ash for C-2 to C-5 mixes and water reduced mixes.

Protection against cutaneous leishmaniasis in outbred vervet monkeys using a recombinant histone H1 antigen.

Infection with Leishmania major parasites results in the development of cutaneous ulcerative lesions on the skin. We investigated the protective potential of a single, recombinant histone H1 antigen against cutaneous leishmaniasis in an outbred population of vervet monkeys, using Montanide adjuvant. Protection was assessed by challenging the animals with a mixture of vector sand fly salivary-gland lysate and a low dose of in vitro-derived parasites, thus more closely mimicking natural infection induced by L. major. The course of infection in immunized monkeys was compared with that of animals that had healed from a primary infection and were immune. The monkeys immunized with recombinant histone H1 showed a reduced development of lesion size, compared with controls. Our study therefore illustrates the potential use of histone H1 as a vaccine candidate against cutaneous leishmaniasis in humans.

Flight, feeding and reproductive behavior of Phyllophaga cuyabana (Moser) (Coleoptera: Melolonthidae) adults

Phyllophaga cuyabana is a univoltine species and its development occurs completely underground. Its control by conventional methods, such as chemical and biological insecticides, is difficult, so it is important to understand its dispersion, reproduction, and population behavior in order to determine best pest management strategies. The objective of this work was to study the behavior of adults of P. cuyabana. This study was carried out in the laboratory, greenhouse and field sites in Paraná State, Brazil (24º25' S and 52º48' W), during four seasons. The results obtained demonstrate that: a) P. cuyabana adults have a synchronized short-flight period when mating and reproduction occurs; b) adults tend to aggregate in specific sites for mating; c) the majority of adults left the soil on alternate nights; d) the choice of mating and oviposition sites was made by females before copulation, since after copulation adults did not fly from or bury themselves at nearby locations; e) females that fed on leaves after mating, oviposited more eggs than females that had not fed;f) plant species such as sunflower (Helianthus annuus) and the Crotalaria juncea are important food sources for adults.

Variation in the proportion of flower visitors of Arum maculatum along its distributional range in relation with community‐based climatic niche analyses

Here, we investigate the geographical constancy in the specificity level of the specialized lure-and-trap pollination antagonism involving the widespread European Arum maculatum and its associated Psychodid pollinators. Until now, studies concurred in demonstrating that one single insect species, Psychoda phalaenoides, efficiently cross-pollinated plants; researches were, however, performed locally in western Europe. In this study we characterize for the first time the flower visitors' composition at the scale of the distribution range of A. maculatum by intensively collecting plants and insects throughout the European continent. We further correlate local climatic characteristics with the community composition of visiting arthropods.Our results show that flowers are generally visited by P. phalaenoides females, but not over the whole distribution range of the plant. In some regions this fly species is less frequent or even absent and another species, Psycha grisescens, becomes the prevailing visitor. This variability is geographically structured and can be explained by climatic factors: the proportion of P. grisescens increases with higher annual precipitations and lower precipitations in the warmest trimester, two characteristics typical of the Mediterranean zone. Climate thus seems driving the specificity of this interaction, by potentially affecting the phenology of one or both interacting species, or even of volatile and heat production in the plant. This result therefore challenges the specificity of other presumably one-to-one interactions covering wide distribution ranges, and provides an example of the direct effect that the abiotic environment can have on the fate of plant-insect interactions.

Visualizing olfactory receptor expression and localization in Drosophila.

Odor detection and discrimination by olfactory systems in vertebrates and invertebrates depend both on the selective expression of individual olfactory receptor genes in subpopulations of olfactory sensory neurons, and on the targeting of the encoded proteins to the exposed, ciliated endings of sensory dendrites. Techniques to visualize the expression and localization of olfactory receptor gene products in vivo have been essential to reveal the molecular logic of peripheral odor coding and to permit investigation of the developmental and cellular neurobiology of this sensory system. Here, we describe methods for detection of olfactory receptor transcripts and proteins in the antennal olfactory organ of the fruit fly, Drosophila melanogaster, an important genetic model organism. We include protocols both for antennal cryosections and whole-mount antennae. These methods can be adapted for detection of receptor expression in other olfactory and gustatory tissues in Drosophila, as well as in the chemosensory systems of other insects.

Development of a Conductometric Test for Frost Resistance of Concrete, HR-272, Phase II, 1986

The purpose of this report is to describe the major research activities during the period of February 1, 1985 - October 30, 1986 for the Iowa Highway Research Board under the research contract entitled "Development of a Conductometric Test for Frost Resistance of Concrete." The objective of this research, as stated in the project proposal, is to develop a test method which can be reasonably rapidly performed in the laboratory and in the field to predict the behavior of concrete subjected to the action of alternate freezing and thawing with a high degree of certainty. In the work plan of the proposal it was stated that the early part of the first year would be devoted to construction of testing equipment and preparation of specimens and the remainder of the year would be devoted to the testing of specimens. It was also stated that the second and third years would be devoted to performance and refinements of tests, data analysis, preparation of suggested specifications, and performance of tests covering variables which need to be studied such as types of aggregates, fly ash replacements and other admixtures. The objective of this report is to describe the progress made during the first 20 months of this project and assess the significance of the results obtained thus far and the expected significance of the results obtainable during the third year of the project.

Pooled Fund Study of Premature Concrete Pavement Deterioration, HR-1063, Final Report, 1997

Recently, a number of roads have begun to exhibit the onset of deterioration at relatively early ages. Since this deterioration appears to be the result of materials issues, data concerning raw materials, design, and paving conditions have been collected and analyzed for correlation between independent variables and deterioration. This analysis shows that there is a positive and statistically significant correlation between deterioration and the following variables: alkali and sulfate content of the cementitious materials, impermeable base course, paving temperature, and the presence of fly ash. This study also concludes that there is a significant need for improvement in data collection and maintenance by many organizations responsible for the production of concrete

Deterioration of Iowa Highway Concrete Pavements: A Petrographic Study, HR-1065, 1999

Major highway concrete pavements in Iowa have exhibited premature deterioration attributed to effects of ettringite formation, alkali-silica expansive reactions, and to frost attack, or some combination of them. These pavements were constructed in the mid- 1980s as non-reinforced, dual-lane, roads ranging in thickness between 200 mm and 300 mm, with skewed joints reinforced with dowels. Deterioration was initially recognized with a darkening of joint regions, which occurred for some pavements as soon as four years after construction. Pavement condition ranges from severe damage to none, and there appeared to be no unequivocal materials or processing variables correlated with failure. Based upon visual examinations, petrographic evaluation, and application of materials models, the deterioration of concrete highway pavements in Iowa appear related to a freeze-thaw failure of the coarse aggregate and the mortar. Crack patterns sub-parallel to the concrete surface transecting the mortar fraction and the coarse aggregate are indicative of freeze-thaw damage of both the mortar and aggregate. The entrained air void system was marginal to substandard, and filling of some of the finer-sized voids by ettringite appears to have further degraded the air void system. The formation of secondary ettringite within the entrained air voids probably reflects a relatively high degree of concrete saturation causing the smaller voids to be filled with pore solution when the concrete freezes. Alkali-silica reaction (ASR) affects some quartz and shale in the fine aggregate, but is not considered to be a significant cause of the deterioration. Delayed ettringite formation was not deemed likely as no evidence of a uniform paste expansion was observed. The lack of field-observed expansion is also evidence against the ASR and DEF modes of deterioration. The utilization of fly ash does not appear to have affected the deterioration as all pavements with or without fly ash exhibiting substantial damage also exhibit significant filling of the entrained air void system, and specimens containing fly ash from sound pavements do not have significant filling. The influence of the mixture design, mixing, and placing must be evaluated with respect to development of an adequate entrained air void system, concrete homogeneity, longterm drying shrinkage, and microcracking. A high-sand mix may have contributed to the difficult mixture characteristics noted upon placement and exacerbate concrete heterogeneity problems, difficulty in developing an adequate entrained air void system, poor consolidation potential, and increased drying shrinkage and cracking. Finally, the availability of moisture must also be considered, as the secondary precipitation of ettringite in entrained air voids indicates they were at least partially filled with pore solution at times. Water availability at the base of the slabs, in joints, and cracks may have provided a means for absorbing water to a point of critical saturation.

Evaluation of Metakaolin for HPC Deck Overlays, MLR-11-01, 2011

The use of High Performance Concrete (HPC) in Iowa has consisted of achieving slightly higher compressive strengths with an emphasis on reduced permeability. Concrete with reduced permeability has increased durability by slowing moisture and chloride ingress. Achieving reduced permeability has typically been accomplished with combinations of slag and Class C fly ash, or the use of blended cements such as locally available Type IS(20), IS(25) and Type IP(25) in conjunction with Class C fly ash. Fly ash has been used in the majority of concrete placed in Iowa since 1984 and slag has been available in Iowa since 1995. During the economic downturn in 2008, one of the cement plants that produced a Type IS(25) cement was forced to shut down, which reduced the availability of blended cements, typically used on HPC deck overlays. Recently, a source of high reactivity metakaolin has been made available. Metakaolin is produced by heating a pure kaolinite clay to 650 to 700 °C in a rotary kiln (calcining). Metakaolin is a white pozzolan that is used to produce concrete with increased strengths, reduced permeability, reduced efflorescence, and resistance to alkali silica reactivity. The W.R. Grace MK-100 metakaolin will likely be available in dissolvable bags between 25 and 50 pounds. Thus, the mix designs were based on the anticipated bag size range for field use. This research evaluated metakaolin mixes with and without Class C fly ash. Results indicated a seven percent replacement with metakaolin produced concrete with increased strengths and low permeability. When used with Class C fly ash, permeability is reduced to very low rating. Metakaolin may be used to enhance hardened concrete properties for use in high performance concrete (HPC).

Evaluation of the Consolid System of Soil Stabilization, MLR-86-10, 1987

The Consolid System by American Consolid Inc. is a three product system that, according to product literature, "enables any soil, found anywhere, to be upgraded to achieve better characteristics necessary in improving road life and quality". Consolid was evaluated along with mixes of cement-fly ash and hydrated lime on two soils. The soils were an A-2-4(0) with zero plasticity index and an A-7-8(18) with a 31 plasticity index. American Consolid Inc. recommended an application rate of 0.10% Consolid 444 and 1.00% Conservex by dry soil weight. The application rate chosen for cement-fly ash was 5% cement and 15% fly ash and for hydrated lime it was 6.5%. Testing involved triaxial testing of specimens after water soaking, unconfined compressive strength of specimens before and after water soaking, and freeze and thaw testing of specimens after water soaking. All specimens were compacted to standard proctor at optimum moisture. The cement-fly ash treated mixes had the highest strength and durability followed by the hydrated lime treated mixes.