Aggregates in Self-Consolidating Concrete

Self-consolidating concrete (SCC) is an advanced type of concrete that can flow through intricate geometrical configurations under its own mass without vibration or segregation. A research project was conducted to investigate the role of aggregates in SCC. Although SCC can be proportioned with a wide range of aggregates, the selection of favorable aggregate characteristics can significantly enhance the economy and performance of SCC. The objectives of the research project were to evaluate the effects of specific aggregate characteristics and mixture proportions on the workability and hardened properties of SCC, to identify favorable aggregate characteristics for SCC, and to develop guidelines for proportioning SCC with any set of aggregates. The effects of aggregate grading; maximum size; shape, angularity, and texture; clay content; and packing density were evaluated. Separately, the effects of mixture proportions, cementitious materials, and chemical admixtures were evaluated. In total, 12 fine aggregates, 7 coarse aggregates, and 6 microfines were tested. Tests were conducted on paste, mortar, and concrete. Paste measurements were conducted to evaluate the effects of cement, fly ash, microfines, high-range water-reducing admixture (HRWRA), and viscosity modifying admixture (VMA) on rheological properties. Mortar measurements were conducted to evaluate the effects of fine aggregates, microfines, and mixture proportions on workability and hardened properties. Concrete measurements were conducted to evaluate the effects of fine aggregates, coarse aggregates, microfines, and mixture proportions on workability and hardened properties. Target properties for SCC workability were defined as a function of the application and in terms of filling ability, passing ability, segregation resistance, and rheology. Seven workability test methods were evaluated extensively to provide sound, engineering justifications for their use and for the interpretation of their results. Specific tests for filling ability, passing ability, and segregation resistance were recommended. Based on the results of this research and well-established principles from the literature, a mixture proportioning procedure for SCC was developed.Aggregates Foundation for Technology, Research, and Education (AFTRE)Civil, Architectural, and Environmental Engineerin

ICAR Mixture Proportioning Procedure for Self-Consolidating Concrete

Self-consolidating concrete (SCC) is an advanced type of concrete that can flow under its own mass without vibration, pass through intricate geometrical configurations, and resist segregation. The use of SCC can result in increased construction productivity, improved jobsite safety, and improved concrete quality. To achieve SCC workability, the materials and mixture proportions must be carefully selected. The ICAR mixture proportioning procedure was developed as part of ICAR Research Project 108: Aggregates in Self-Consolidating Concrete. This research project evaluated the workability and hardened properties of SCC mixtures composed of a wide range of materials and mixture proportions. The ICAR mixture proportioning procedure is based on a fundamental, rheology-based framework for concrete workability and is designed and written to be accessible and comprehensible. The procedure provides specific guidelines for each aspect of the mixture proportioning process but intentionally avoids long calculations or restrictive, discrete inputs. Instead, deliberate laboratory testing is conducted with actual job materials to establish final mixture proportions efficiently. All required testing is conducted with methods standardized by ASTM International.Aggregates Foundation for Technology, Research, and Education (AFTRE)Civil, Architectural, and Environmental Engineerin

Phylogenomic and biogeographic reconstruction of the Trichinella complex

Trichinellosis is a globally important food-borne parasitic disease of humans caused by roundworms of the Trichinella complex. Extensive biological diversity is reflected in substantial ecological and genetic variability within and among Trichinella taxa, and major controversy surrounds the systematics of this complex. Here we report the sequencing and assembly of 16 draft genomes representing all 12 recognized Trichinella species and genotypes, define protein-coding gene sets and assess genetic differences among these taxa. Using thousands of shared single-copy orthologous gene sequences, we fully reconstruct, for the first time, a phylogeny and biogeography for the Trichinella complex, and show that encapsulated and non-encapsulated Trichinella taxa diverged from their most recent common ancestor ~21 million years ago (mya), with taxon diversifications commencing ~10−7 mya

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Aggregates in self-consolidating concrete

textSelf-consolidating concrete (SCC) is an advanced type of concrete that can flow under its own mass without vibration, pass through intricate geometrical configurations, and resist segregation. SCC constituent materials and mixture proportions must be properly selected to achieve these flow properties. The effects of any changes in materials or mixture proportions on hardened concrete performance must be considered in evaluating SCC. A research project was conducted to investigate the role of aggregates in SCC. The objectives of this research were to evaluate the effects of aggregate characteristics and mixture proportions on the workability and hardened properties of SCC, to identify favorable aggregate characteristics for SCC, and to develop guidelines for proportioning SCC with any set of aggregates. The research indicated that although SCC can be proportioned with a wide range of aggregates, the selection of favorable aggregates can significantly enhance the economy and performance of SCC. The effects of aggregate grading; maximum size; shape, angularity, and texture; apparent clay content; and packing density were evaluated. The main effect of aggregates larger than approximately 75 [mu]m was found to be on the minimum required paste volume for achieving SCC workability. It was found that dust-of fracture microfines, defined as mineral material finer than approximately 75 [mu]m produced during the crushing of aggregates, could be an economical choice to comprise part of the paste volume. Based on the results of this research, a mixture proportioning procedure for SCC was developed. The procedure is based on a consistent, rheology-based framework and was designed and written to be accessible and comprehensible for routine use. In the procedure, SCC is represented as a suspension of aggregates in paste. Aggregates are selected on the basis of grading, maximum size, and shape and angularity. The paste volume is set based on the aggregate characteristics in order to achieve workability requirements. The paste composition is established to achieve workability and hardened property requirements.Civil, Architectural, and Environmental Engineerin

Development of a portable rheometer for fresh portland cement concrete

The purpose of this research was to identify an effective field test method for measuring the workability of concrete in general and of high-microfines concrete in particular. The workability of fresh concrete has traditionally been measured with the slump test, which provides an inadequate indication of workability. For certain concrete mixtures—such as those containing fiber reinforcement, ground granulated blast furnace slag, or high contents of aggregate microfines—the slump test can provide inaccurate and misleading results. The need for a better test method for workability is well established within the concrete industry. Based on a literature search in which 61 existing workability test methods were identified and on feedback from government, industry, and academia, criteria for an improved workability test device were developed. It was determined that the best approach to measuring workability would be to develop a new portable rheometer. The ICAR rheometer—a low-cost, fully portable test device for concrete—was developed and tested. A first generation prototype was built using off-the-shelf components. The ICAR rheometer is approximately the size of a drill and can be operated by hand or positioned above a standard container. It is capable of measuring a flow curve or performing a stress growth test and is appropriate for nearly the full range of concrete workability ranging from a slump of approximately 2 inches to self-consolidating concrete. Experimental testing on a wide range of concrete mixtures indicated that the ICAR rheometer was able to detect changes in workability and rheology successfully. As a dynamic test that adds energy to concrete, it is well suited for measuring high-microfines concrete and other highly thixotropic concrete mixtures. Field testing confirmed the portability of the ICAR rheometer. The low cost and portable form factor of the ICAR rheometer can make the routine measurement of concrete rheology in the field an economically viable solution to characterizing concrete workabilityCivil, Architectural, and Environmental Engineerin

Development of a Portable Rheometer for Fresh Portland Cement Concrete

The purpose of this research was to identify an effective field test method for measuring the workability of concrete in general and of high-microfines concrete in particular. The workability of fresh concrete has traditionally been measured with the slump test, which provides an inadequate indication of workability. For certain concrete mixtures—such as that containing fiber reinforcement, ground granulated blast furnace slag, or high contents of aggregate microfines—the slump test can provide inaccurate and misleading results. The need for a better test method for workability is well established within the concrete industry. Based on a literature search in which 61 existing workability test methods were identified and on feedback from government, industry, and academia, criteria for an improved workability test device were developed. It was determined that the best approach to measuring workability would be to develop a new portable rheometer. The ICAR rheometer—a low-cost, fully portable test device for concrete—was developed and tested. A first generation prototype was built using off-the-shelf components. The ICAR rheometer is approximately the size of a drill and can be operated by hand or positioned above a standard container. It is capable of measuring a flow curve or performing a stress growth test and is appropriate for nearly the full range of concrete workability ranging from a slump of approximately 2 inches to self-consolidating concrete. Experimental testing on a wide range of concrete mixtures indicated that the ICAR rheometer was able to detect changes in workability and rheology successfully. As a dynamic test that adds energy to concrete, it is well suited for measuring high-microfines concrete and other highly thixotropic concrete mixtures. Field testing confirmed the portability of the ICAR rheometer. The low cost and portable form factor of the ICAR rheometer can make the routine measurement of concrete rheology in the field an economically viable solution to characterizing concrete workability.Aggregates Foundation for Technology, Research, and Education (AFTRE)Civil, Architectural, and Environmental Engineerin

Summary of Concrete Workability Test Methods

This document describes 61 test methods for measuring concrete workability. Many more test methods have been developed for a single project or for a specific application and have been sparsely reported in the literature, if at all. Although many of the devices in this document will likely never be used in the future and have been scarcely used in the past, an examination of tests that have failed and tests that have been supplanted by better tests is instructive in recognizing trends in concrete workability research and in selecting key concepts for the development of a new test method. This document first describes key principles and trends in the measurement of workability and then describes the 61 test methods. Based on the successes and failures of past test methods and the current needs of the concrete industry, requirements for new test methods are developed.Aggregates Foundation for Technology, Research, and Education (AFTRE)Civil, Architectural, and Environmental Engineerin

Phylogenomic and biogeographic reconstruction of the <i>Trichinella</i> complex

Trichinellosis is a globally important food-borne parasitic disease of humans caused by roundworms of the Trichinella complex. Extensive biological diversity is reflected in substantial ecological and genetic variability within and among Trichinella taxa, and major controversy surrounds the systematics of this complex. Here we report the sequencing and assembly of 16 draft genomes representing all 12 recognized Trichinella species and genotypes, define protein-coding gene sets and assess genetic differences among these taxa. Using thousands of shared single-copy orthologous gene sequences, we fully reconstruct, for the first time, a phylogeny and biogeography for the Trichinella complex, and show that encapsulated and non-encapsulated Trichinella taxa diverged from their most recent common ancestor ∼21 million years ago (mya), with taxon diversifications commencing ∼10−7 mya.Full Tex