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).

Report on Fly Ash as a Soil Additive, MLR-81-03, 1981

The addition of a selected self-cementing, Class C fly ash to blow sand soils improves their compacted strength greatly as opposed to the minimal strength improvement when fly ash is mixed with loess soil. By varying the percentage of fly ash added, the resulting blow sand-fly ash mixture can function as a low strength stabilized material or as a higher strength sub-base. Low strength stabilized material can also be obtained by mixing loess soils with a selected Class C fly ash. The development of the higher strength values required for subbase materials is very dependent upon compaction delay time and moisture condition of the material. Results at this time indicate that, when compaction delays are involved, excess moisture in the material has the greatest positive effect in achieving minimum strengths. Other added retarding agents, such as borax and gypsum, have less effect.

Hydraulic Cement Grout Testing, MLR-89-14, 1990

Currently, hydraulic cement grouts are approved for Iowa Department of Transportation projects on the basis of a pullout test. However, other properties of the grouts should be evaluated. Therefore, this research was initiated to develop criteria to better evaluate hydraulic cement grouts. Fourteen grouts were tested for compressive strength, time of set, durability, consistency and shrinkage. Tested grouts all yielded compressive strengths higher than 3000 psi at 7 days and durability factors were well above 70. Time of set and consistency was adequate. The testing showed most grouts tested shrank, even though tested grouts were labeled non-shrink grouts. For many applications of grouts such as setting in anchor bolts and as a filler, minor shrinkage is not a problem. However, for some critical applications, shrinkage cannot be tolerated. The proposed Instructional Memorandum will identify those grouts which do not excessively shrink or expand in the tests used. Based on test results, criteria for evaluation of hydraulic cement grouts have been recommended. Evaluation consists of tests for compressive strength, time of set, durability, consistency, shrinkage and pullout test.

Improving Portland Cement Concrete Mix Consistency and Production Rate through Two-Stage Mixing, TR-505, 2007

A two-stage mixing process for concrete involves mixing a slurry of cementitious materials and water, then adding the slurry to coarse and fine aggregate to form concrete. Some research has indicated that this process might facilitate dispersion of cementitious materials and improve cement hydration, the characteristics of the interfacial transition zone (ITZ) between aggregate and paste, and concrete homogeneity. The goal of the study was to find optimal mixing procedures for production of a homogeneous and workable mixture and quality concrete using a two-stage mixing operation. The specific objectives of the study are as follows: (1) To achieve optimal mixing energy and time for a homogeneous cementitious material, (2) To characterize the homogeneity and flow property of the pastes, (3) To investigate effective methods for coating aggregate particles with cement slurry, (4) To study the effect of the two-stage mixing procedure on concrete properties, (5) To obtain the improved production rates. Parameters measured for Phase I included: heat of hydration, maturity, and rheology tests were performed on the fresh paste samples, and compressive strength, degree of hydration, and scanning electron microscope (SEM) imaging tests were conducted on the cured specimens. For Phases II and III tests included slump and air content on fresh concrete and compressive and tensile strengths, rapid air void analysis, and rapid chloride permeability on hardened concrete.

Applications for Reuse of Lime Sludge from Water Softening, TR-535, 2005

Lime sludge, an inert material mostly composed of calcium carbonate, is the result of softening hard water for distribution as drinking water. A large city such as Des Moines, Iowa, produces about 30,700 tons of lime sludge (dry weight basis) annually (Jones et al., 2005). Eight Iowa cities representing, according to the United States (U.S.) Census Bureau, 23% of the state’s population of 3 million, were surveyed. They estimated that they collectively produce 64,470 tons of lime sludge (dry weight basis) per year, and they currently have 371,800 tons (dry weight basis) stockpiled. Recently, the Iowa Department of Natural Resources directed those cities using lime softening in drinking water treatment to stop digging new lagoons to dispose of lime sludge. Five Iowa cities with stockpiles of lime sludge funded this research. The research goal was to find useful and economical alternatives for the use of lime sludge. Feasibility studies tested the efficacy of using lime sludge in cement production, power plant SOx treatment, dust control on gravel roads, wastewater neutralization, and in-fill materials for road construction. Applications using lime sludge in cement production, power plant SOx treatment, and wastewater neutralization, and as a fill material for road construction showed positive results, but the dust control application did not. Since the fill material application showed the most promise in accomplishing the project’s goal within the time limits of this research project, it was chosen for further investigation. Lime sludge is classified as inorganic silt with low plasticity. Since it only has an unconfined compressive strength of approximately 110 kPa, mixtures with fly ash and cement were developed to obtain higher strengths. When fly ash was added at a rate of 50% of the dry weight of the lime sludge, the unconfined strength increased to 1600 kPa. Further, friction angles and California Bearing Ratios were higher than those published for soils of the same classification. However, the mixtures do not perform well in durability tests. The mixtures tested did not survive 12 cycles of freezing and thawing and wetting and drying without excessive mass and volume loss. Thus, these mixtures must be placed at depths below the freezing line in the soil profile. The results demonstrated that chemically stabilized lime sludge is able to contribute bulk volume to embankments in road construction projects.

Biofuel Co-Product Uses for Pavement Geo-Materials Stabilization, TR-582, 2010

The production and use of biofuels has increased in the present context of sustainable development. Biofuel production from plant biomass produces not only biofuel or ethanol but also co-products containing lignin, modified lignin, and lignin derivatives. This research investigated the utilization of lignin-containing biofuel co-products (BCPs) in pavement soil stabilization as a new application area. Laboratory tests were conducted to evaluate the performance and the moisture susceptibility of two types of BCP-treated soil samples compared to the performance of untreated and traditional stabilizer-treated (fly ash) soil samples. The two types of BCPs investigated were (1) a liquid type with higher lignin content (co-product A) and (b) a powder type with lower lignin content (co-product B). Various additive combinations (co-product A and fly ash, co-products A and B, etc.) were also evaluated as alternatives to stand-alone co-products. Test results indicate that BCPs are effective in stabilizing the Iowa Class 10 soil classified as CL or A-6(8) and have excellent resistance to moisture degradation. Strengths and moisture resistance in comparison to traditional additives (fly ash) could be obtained through the use of combined additives (co-product A + fly ash; co-product A + co-product B). Utilizing BCPs as a soil stabilizer appears to be one of the many viable answers to the profitability of the bio-based products and the bioenergy business. Future research is needed to evaluate the freeze-thaw durability and for resilient modulus characterization of BCP-modified layers for a variety of pavement subgrade and base soil types. In addition, the long-term performance of these BCPs should be evaluated under actual field conditions and traffic loadings. Innovative uses of BCP in pavement-related applications could not only provide additional revenue streams to improve the economics of biorefineries, but could also serve to establish green road infrastructures.

Effectiveness of Electrochemical Chloride Extraction for the Iowa Avenue Pedestrian Bridge, TR-499, 2005

The main objective of this study is to determine the effectiveness of the Electrochemical Chloride Extraction (ECE) technique on a bridge deck with very high concentrations of chloride. This ECE technique was used during the summer of 2003 to reverse the effects of corrosion, which had occurred in the reinforcing steel embedded in the pedestrian bridge deck over Highway 6, along Iowa Avenue, in Iowa City, Iowa, USA. First, the half cell potential was measured to determine the existing corrosion level in the field. The half-cell potential values were in the indecisive range of corrosion (between -200 mV and -350 mV). The ECE technique was then applied to remove the chloride from the bridge deck. The chloride content in the deck was significantly reduced from 25 lb/cy to 4.96 lb/cy in 8 weeks. Concrete cores obtained from the deck were measured for their compressive strengths and there was no reduction in strength due to the ECE technique. Laboratory tests were also performed to demonstrate the effectiveness of the ECE process. In order to simulate the corrosion in the bridge deck, two reinforced slabs and 12 reinforced beams were prepared. First, the half-cell potentials were measured from the test specimens and they all ranged below -200 mV. Upon introduction of 3% salt solution, the potential reached up to -500 mV. This potential was maintained while a salt solution was being added for six months. The ECE technique was then applied to the test specimens in order to remove the chloride from them. Half-cell potential was measured to determine if the ECE technique can effectively reduce the level of corrosion.

Autonomous Measurements of Bridge Pier and Abutment Scour using Motion-Sensing Radio Transmitters, TR-595, 2010

Two portable Radio Frequency IDentification (RFID) systems (made by Texas Instruments and HiTAG) were developed and tested for bridge scour monitoring by the Department of Civil and Environmental Engineering at the University of Iowa (UI). Both systems consist of three similar components: 1) a passive cylindrical transponder of 2.2 cm in length (derived from transmitter/responder); 2) a low frequency reader (~134.2 kHz frequency); and 3) an antenna (of rectangular or hexagonal loop). The Texas Instruments system can only read one smart particle per time, while the HiTAG system was successfully modified here at UI by adding the anti-collision feature. The HiTAG system was equipped with four antennas and could simultaneously detect 1,000s of smart particles located in a close proximity. A computer code was written in C++ at the UI for the HiTAG system to allow simultaneous, multiple readouts of smart particles under different flow conditions. The code is written for the Windows XP operational system which has a user-friendly windows interface that provides detailed information regarding the smart particle that includes: identification number, location (orientation in x,y,z), and the instance the particle was detected.. These systems were examined within the context of this innovative research in order to identify the best suited RFID system for performing autonomous bridge scour monitoring. A comprehensive laboratory study that included 142 experimental runs and limited field testing was performed to test the code and determine the performance of each system in terms of transponder orientation, transponder housing material, maximum antenna-transponder detection distance, minimum inter-particle distance and antenna sweep angle. The two RFID systems capabilities to predict scour depth were also examined using pier models. The findings can be summarized as follows: 1) The first system (Texas Instruments) read one smart particle per time, and its effective read range was about 3ft (~1m). The second system (HiTAG) had similar detection ranges but permitted the addition of an anti-collision system to facilitate the simultaneous identification of multiple smart particles (transponders placed into marbles). Therefore, it was sought that the HiTAG system, with the anti-collision feature (or a system with similar features), would be preferable when compared to a single-read-out system for bridge scour monitoring, as the former could provide repetitive readings at multiple locations, which could help in predicting the scour-hole bathymetry along with maximum scour depth. 2) The HiTAG system provided reliable measures of the scour depth (z-direction) and the locations of the smart particles on the x-y plane within a distance of about 3ft (~1m) from the 4 antennas. A Multiplexer HTM4-I allowed the simultaneous use of four antennas for the HiTAG system. The four Hexagonal Loop antennas permitted the complete identification of the smart particles in an x, y, z orthogonal system as function of time. The HiTAG system can be also used to measure the rate of sediment movement (in kg/s or tones/hr). 3) The maximum detection distance of the antenna did not change significantly for the buried particles compared to the particles tested in the air. Thus, the low frequency RFID systems (~134.2 kHz) are appropriate for monitoring bridge scour because their waves can penetrate water and sand bodies without significant loss of their signal strength. 4) The pier model experiments in a flume with first RFID system showed that the system was able to successfully predict the maximum scour depth when the system was used with a single particle in the vicinity of pier model where scour-hole was expected. The pier model experiments with the second RFID system, performed in a sandbox, showed that system was able to successfully predict the maximum scour depth when two scour balls were used in the vicinity of the pier model where scour-hole was developed. 5) The preliminary field experiments with the second RFID system, at the Raccoon River, IA near the Railroad Bridge (located upstream of 360th street Bridge, near Booneville), showed that the RFID technology is transferable to the field. A practical method would be developed for facilitating the placement of the smart particles within the river bed. This method needs to be straightforward for the Department of Transportation (DOT) and county road working crews so it can be easily implemented at different locations. 6) Since the inception of this project, further research showed that there is significant progress in RFID technology. This includes the availability of waterproof RFID systems with passive or active transponders of detection ranges up to 60 ft (~20 m) within the water–sediment column. These systems do have anti-collision and can facilitate up to 8 powerful antennas which can significantly increase the detection range. Such systems need to be further considered and modified for performing automatic bridge scour monitoring. The knowledge gained from the two systems, including the software, needs to be adapted to the new systems.

Geodynamic reconstructions of the Australides-2: Mesozoic-Cainozoic

The present work, derived from a full global geodynamic reconstruction model over 600 Ma and based on a large database, focuses herein on the interaction between the Pacific, Australian and Antarctic plates since 200 Ma, and proposes integrated solutions for a coherent, physically consistent scenario. The evolution of the Australia-Antarctica-West Pacific plate system is dependent on the Gondwana fit chosen for the reconstruction. Our fit, as defined for the latest Triassic, implies an original scenario for the evolution of the region, in particular for the "early" opening history of the Tasman Sea. The interaction with the Pacific, moreover, is characterised by many magmatic arc migrations and ocean openings, which are stopped by arc-arc collision, arc-spreading axis collision, or arc-oceanic plateau collision, and subduction reversals. Mid-Pacific oceanic plateaus created in the model are much wider than they are on present-day maps, and although they were subducted to a large extent, they were able to stop subduction. We also suggest that adduction processes (i.e., re-emergence of subducted material) may have played an important role, in particular along the plate limit now represented by the Alpine Fault in New Zealand.

New observations on Permian stratigraphy in Greece and geodynamic implication

New detailed stratigraphic and micropaleontological works on the famous exposures of Permian rocks in Hydra rich in Foraminifera, allows to define the stratigraphy of other outcrops in Aegina, Salamis, Attica and Chios. A synthetic section is presented which is characterized by the development of 3 successive carbonate platforms during the Permian and by 4 main tectonostratigraphic events. The youngest of these events marks the closure of the Paleotethyan ocean and the collision of a former Gondwanian/Cimmerian passive margin in the S with an active margin in the N.

Uncovering the genetic basis of adaptive change: on the intersection of landscape genomics and theoretical population genetics

A workshop recently held at the Ecole Polytechnique Federale de Lausanne (EPFL, Switzerland) was dedicated to understanding the genetic basis of adaptive change, taking stock of the different approaches developed in theoretical population genetics and landscape genomics and bringing together knowledge accumulated in both research fields. Indeed, an important challenge in theoretical population genetics is to incorporate effects of demographic history and population structure. But important design problems (e.g. focus on populations as units, focus on hard selective sweeps, no hypothesis-based framework in the design of the statistical tests) reduce their capability of detecting adaptive genetic variation. In parallel, landscape genomics offers a solution to several of these problems and provides a number of advantages (e.g. fast computation, landscape heterogeneity integration). But the approach makes several implicit assumptions that should be carefully considered (e.g. selection has had enough time to create a functional relationship between the allele distribution and the environmental variable, or this functional relationship is assumed to be constant). To address the respective strengths and weaknesses mentioned above, the workshop brought together a panel of experts from both disciplines to present their work and discuss the relevance of combining these approaches, possibly resulting in a joint software solution in the future.

Improving T2 -weighted imaging at high field through the use of kT -points.

PURPOSE: At high magnetic field strengths (B0 ≥ 3 T), the shorter radiofrequency wavelength produces an inhomogeneous distribution of the transmit magnetic field. This can lead to variable contrast across the brain which is particularly pronounced in T2 -weighted imaging that requires multiple radiofrequency pulses. To obtain T2 -weighted images with uniform contrast throughout the whole brain at 7 T, short (2-3 ms) 3D tailored radiofrequency pulses (kT -points) were integrated into a 3D variable flip angle turbo spin echo sequence. METHODS: The excitation and refocusing "hard" pulses of a variable flip angle turbo spin echo sequence were replaced with kT -point pulses. Spatially resolved extended phase graph simulations and in vivo acquisitions at 7 T, utilizing both single channel and parallel-transmit systems, were used to test different kT -point configurations. RESULTS: Simulations indicated that an extended optimized k-space trajectory ensured a more homogeneous signal throughout images. In vivo experiments showed that high quality T2 -weighted brain images with uniform signal and contrast were obtained at 7 T by using the proposed methodology. CONCLUSION: This work demonstrates that T2 -weighted images devoid of artifacts resulting from B1 (+) inhomogeneity can be obtained at high field through the optimization of extended kT -point pulses. Magn Reson Med 71:1478-1488, 2014. © 2013 Wiley Periodicals, Inc.

CIRAS News Annual Report 2000, January 3, 2001

CIRAS professionals, the equipment they use to do their jobs, and the latest in technical support equipment. With these investments, CIRAS continues to meet the needs of Iowa manufacturers, whether in doing routine problem solving, long-range planning, or transferring newer technologies. In all of its services, but most notably in product development projects, one of the strengths of CIRAS lies in bringing ISU students into the picture, both to help reach project goals and as real-job learning experiences for the students.

CIRAS News Annual Report 2001, January 3, 2001

CIRAS professionals, the equipment they use to do their jobs, and the latest in technical support equipment. With these investments, CIRAS continues to meet the needs of Iowa manufacturers, whether in doing routine problem solving, long-range planning, or transferring newer technologies. In all of its services, but most notably in product development projects, one of the strengths of CIRAS lies in bringing ISU students into the picture, both to help reach project goals and as real-job learning experiences for the students.

CIRAS News Annual Report 2002, January 3, 2001

CIRAS professionals, the equipment they use to do their jobs, and the latest in technical support equipment. With these investments, CIRAS continues to meet the needs of Iowa manufacturers, whether in doing routine problem solving, long-range planning, or transferring newer technologies. In all of its services, but most notably in product development projects, one of the strengths of CIRAS lies in bringing ISU students into the picture, both to help reach project goals and as real-job learning experiences for the students.