Comparative Analysis of Rapid Chloride Penetration Testing for Novel Reinforced Concrete Systems

69A3551847102This report provides a summary of rapid chloride penetration testing (RCPT) of ductile concrete materials. The report first introduces a range of ductile concrete materials with varying fiber types, fiber lengths, mechanical properties, material constituents, and durability performance. These materials represent various systems that have been used in several transportation projects to improve the durability of transportation infrastructure. Next, an overview of the RCPT testing program is provided and results are presented with comparisons to representative baseline concrete mixtures used in the industry today. The results show that RCPT experiments may not be indicative of resistance to chloride movement since the experiments measure charge passed, rather than chloride ingress. Recommendations for the need to calibrate RCPT results with long-term chloride ponding experiments are discussed

Designing Concrete Mixtures With RCA

69A3551847102The use of recycled concrete aggregates (RCA) as a replacement in new concrete has gained popularity worldwide as a method of reducing natural aggregate consumption. Many individual studies have been completed but little work has been done to analyze that work to make broad conclusions on RCA concrete mechanical properties. This report presents the development and analysis of a database of mechanical properties of concrete containing coarse RCA and provides an investigation the applicability of numerically generated recycled concrete aggregate (RCA) systems by varying the material properties. A sensitivity study of RCA systems was conducted through a full-factorial analysis to explore how the mixture design proportions influence the RCA concrete hardened properties. The modeling methodology was adopted by using a computational algorithm that can generate concrete systems with different RCA replacement levels to numerically simulate RAC systems under mechanical loading. Numerically simulated results are compared with an experimental database that has been established, including a substantial data set on RAC mixture design proportions. RAC geometries and material properties were stochastically generated using Monte Carlo simulation methods, resulting in 200 representative numerical models that were subjected to simulated mechanical loading

Advanced Reinforced Concrete Materials for Transportation Infrastructure: Final Report

Transportation infrastructure systems must resist conditioning from the natural environment and physical demands from service loading to meet the needs of users across the state. Reinforced concrete, which is widely used in bridge decks, pavements, super-and substructures, and other systems, deteriorates under environmental conditioning due to electro-chemical processes that cause expansive mechanics stresses at various length scales (e.g., reinforcement corrosion, freeze-thaw, etc.), leading to costly and timely durability and maintenance challenges. This report provides a background on the state-of-the-art of advanced reinforced concrete materials that are being investigated to improve reinforced concrete transportation infrastructure. A series of experimental and numerical research activities were then carried out to assess the mechanical properties and long-term durability of these systems. Results show benefits across a range of metrics and have the potential to substantially improve the in-service behavior of reinforced concrete transportation infrastructure

Evaluation of Group Genetic Ancestry of Populations from Philadelphia and Dakar in the Context of Sex-Biased Admixture in the Americas

Population history can be reflected in group genetic ancestry, where genomic variation captured by the mitochondrial DNA (mtDNA) and non-recombining portion of the Y chromosome (NRY) can separate female- and male-specific admixture processes. Genetic ancestry may influence genetic association studies due to differences in individual admixture within recently admixed populations like African Americans.We evaluated the genetic ancestry of Senegalese as well as European Americans and African Americans from Philadelphia. Senegalese mtDNA consisted of approximately 12% U haplotypes (U6 and U5b1b haplotypes, common in North Africa) while the NRY haplotypes belonged solely to haplogroup E. In Philadelphia, we observed varying degrees of admixture. While African Americans have 9-10% mtDNAs and approximately 31% NRYs of European origin, these results are not mirrored in the mtDNA/NRY pools of European Americans: they have less than 7% mtDNAs and less than 2% NRYs from non-European sources. Additionally, there is <2% Native American contribution to Philadelphian African American ancestry and the admixture from combined mtDNA/NRY estimates is consistent with the admixture derived from autosomal genetic data. To further dissect these estimates, we have analyzed our samples in the context of different demographic groups in the Americas.We found that sex-biased admixture in African-derived populations is present throughout the Americas, with continual influence of European males, while Native American females contribute mainly to populations of the Caribbean and South America. The high non-European female contribution to the pool of European-derived populations is consistently characteristic of Iberian colonization. These data suggest that genomic data correlate well with historical records of colonization in the Americas

Seismic collapse assessment of archetype frames with ductile concrete beam hinges

Highly ductile cement-based materials have emerged as alternatives to conventional concrete materials to improve the seismic resistance of reinforced concrete (RC) structures. While experimental and numerical research on the behavior of individual components has provided significant knowledge on element-level response, relatively little is known about how ductile cement-based materials influence system-level behavior in seismic applications. This study uses recently developed lumped-plasticity models to simulate the unique failure characteristics and ductility of reinforced ductile-cement-based materials in beam hinges and applies them in the assessment of archetype frame structures. Numerous story heights (four, eight, and twelve), frame configurations (perimeter vs. space), materials (conventional vs. ductile concrete), and replacement mechanisms within the beam hinges are considered in the seismic analysis of the archetype structures. Results and comparisons are made in terms of the probability of collapse at 2% in 50-year ground motion, mean annual frequency of collapse, and adjusted collapse margin ratio (ACMR) across archetype structures. The results show that engineered HPFRCCs in beam plastic-hinge regions can improve the seismic safety of moment frame buildings with higher collapse margin ratios, lower probability of collapse, and the ability to withstand large deformations. Data is also reported on how ductile concrete materials can reduce concrete volume and longitudinal reinforcement tonnage across frame configurations and story heights while maintaining or improving seismic resistance of the structural system. Results demonstrate future research needs to assess life-cycle costs, predict column hinge behavior, and develop code-based design methods for structural systems using highly ductile concrete materials

Effect of Cold Plasma Treatment of Polymer Fibers on the Mechanical Behavior of Fiber-Reinforced Cementitious Composites

Fiber-reinforced cementitious composites (FRCC) are a class of materials made by adding randomly distributed fibers to a cementitious matrix, providing better material toughness through the crack bridging behavior of the fibers. One of the primary concerns with FRCCs is the behavior of the fiber when a crack is formed. The fibers provide a stress-bridging mechanism, which is largely determined by the bond that exists between the concrete and the fiber’s outer surface. While many studies have determined the properties of FRCCs and potential benefits of using specific fiber types, the effects of low temperature or cold plasma treatment of polymer fibers on the mechanical behavior of the composite material are limited. Polymer fibers are notable for their low density, ductility, ease of manufacture, and cost-effectiveness. Despite these advantages, the surface properties of polymers do not enable the bonding potential given by steel or glass fibers when used in untreated FRCC, resulting in pull-out failures before the full displacement capacity of the fiber is utilized. For this reason, modification of the surface characteristics of polymer fibers can aid in higher bonding potential. Plasma treatment is a process wherein surfaces are modified through the kinetics of electrically charged and reactive species in a gaseous discharge environment. This paper is a preliminary study on the use of atmospheric pressure plasma generated at approximately room temperature. This atmospheric, cold plasma treatment is a method for improving the mechanical properties of FRCC using polymeric fibers. In this study, polypropylene and polyvinyl-alcohol fibers were cold plasma treated for 0, 30, 60, and 120 s before being used in cementitious mortar mixtures. Compression and flexure tests were performed using a displacement-based loading protocol to examine the impact of plasma treatment time on the corresponding mechanical performance of the fiber-reinforced cementitious composite. The experimental results obtained from this study indicate that there is a positive correlation between fiber treatment time and post-peak load-carrying capacity, especially for specimens subjected to flexural loading

Advanced Reinforced Concrete Materials for Transportation Infrastructures [Technical Brief]

The overall objective of this project was to understand how advanced materials can be used to improve the durability of reinforced concrete transportation infrastructure in the State of New Jersey. A primary focus of the research program was to investigate highly ductile concrete materials, often referred to as high-performance fiber-reinforced cementitious composites (HPFRCCs). Specific objectives included: (i) identifying novel materials that can be deployed to enhance transportation infrastructure durability, (ii) experimentally investigating the durability of these systems across a range of deterioration metrics, (iii) evaluating the in-service performance through detailed numerical simulations, and (iv) predicting the life-cycle costs of transportation infrastructure when using advanced concrete materials