International Concrete Abstracts Portal

Ultra-high-performance concrete (UHPC) is an advanced cementitious composite material with extraordinary mechanical and durability properties. This article discusses the construction of a short-span bridge using UHPC as well as the cost considerations associated with building an entire bridge with UHPC and reflects on lessons learned from the process.

Modular construction has been attracting attention worldwide as a promising solution to reduce construction time and labor demand. In this study, a new inter-module composite floor system that connects the upper module floor beams and lower module ceiling beams was experimentally and analytically investigated with an emphasis on vibration performance under service loading. First, the upper module floor of 2 m [6.56 ft] wide and 6 m [19.7 ft] long was fabricated as a composite system consisting of precast concrete (PC) panels, steel beams and ultra high-performance concrete (UHPC) connectors. Structural integrity between PC panels, steel beams and UHPC connectors were secured using grouting and topping mortar. Then, the lower module ceiling beams were connected to the upper module floor beams by fully tensioned high-tension bolts (i.e., slip-critical connection) to complete the inter-module composite floor. The vibration frequencies, damping ratio, and acceleration responses of the inter-module composite floors were measured from laboratory tests such as impact hammer, heel drop and walking tests, considering the number and location of the connecting bolts as the test parameter. The vibration characteristics of the inter-module composite floors were investigated further through finite element analysis. The measured and predicted vibration performances were compared with the acceptance criteria in AISC Design Guide 11 and ISO 10137.

Ultra-high performance concrete (UHPC) is a state-of-the-art cementitious composite. Since the concept of this novel concrete mixture emerged in the 1990s, significant advancements have been made with numerous benefits such as high strength, flowability, high post-cracking tensile resistance, improved durability, reduced maintenance, and extended longevity. Currently, UHPC is employed around the globe alongside recently published practice guidelines. Although numerous research projects were undertaken to examine the behavior of UHPC-incorporated structures, there still are many gaps to be explored. Of interest are the development of robust and reliable mixtures and their application to primary load-bearing members for bridges and buildings, including various site demonstration projects that would promote the use of this leading-edge construction material. This Special Publication (SP) contains nine papers selected from three technical sessions held in the ACI Spring Convention in March 2022. All manuscripts were reviewed by at least two experts in accordance with the ACI publication policy. The Editors wish to thank all contributing authors and anonymous reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance. Yail J. Kim, Steven Nolan, and Antonio Nanni Editors University of Colorado Denver Florida Department of Transportation University of Miami

Ultra-high performance concrete (UHPC) has seen growing use in the construction industry because of its high compressive, tensile, and flexural strength. The tensile and flexural strength are in part due to the steel fibers added to the UHPC mix. Yet, fibers can segregate due to poor material rheological properties and construction practices, resulting in less than expected material strength. Due to the importance of these fibers, there is a need to verify the volume and orientation of the steel fibers in the UHPC. In this work, we report on the design and testing of electromagnetic sensor systems that are able to test the integrity of the steel fibers in the UHPC structure. We test our sensor system using UHPC samples containing 1% to 3% fiber content by volume and created a calibration based on the results. Our results show a linear relationship between the inductance change versus the fiber percentage with an R-squared value of 99.7 %, which shows that our approach successfully demonstrated the potential of using our approach for characterizing steel fibers in UHPCs.

The movement of ultra-high-performance concrete (UHPC) toward wide scale acceptance within the concrete industry has generated interest in developing improved test methods to provide quality assurance for this material. Most test methods currently used to measure the tensile behavior of ultra-high-performance concrete require specialized testing equipment that is not typically owned by precast or ready-mix production facilities. These test methods provide reliable data for quality assurance of newly developed concrete mixes, but they are impractical as quality-control tests, which would need to be performed for every UHPC placement. This paper presents the development of a simple and inexpensive test to measure tensile strength and ductility for UHPC and serve as a quality-control test. This method was developed from the double-punch test, commonly referred to as the “Barcelona test,” but has been revised to incorporate substantial changes to the loading and data collection requirements to eliminate the need for expensive, specialized equipment. It was determined that the modified test method could produce reliable results using a load-controlled testing procedure with manually recorded data points taken every 0.635 mm (0.025 inches) of vertical displacement for ductile concrete specimens. It was also determined that specimen surface grinding, loading rate, and punch alignment did not significantly influence the test results. However, the fabrication of the specimens, specifically the rate and method at which the molds were filled, had a significant effect on the results. Accordingly, any recommended standardized test method based off of this procedure should have requirements on specimen fabrication.