Evaluation of Surface Preparation and Bond Angle Combinations for Joint Replacement using Ultra-High Performance Concrete

Deterioration of bridges is often attributed to declining performance of the longitudinal connections between precast members or transverse deck joints. Ultra-high performance concrete (UHPC) is a cementitious composite with mechanical and durability properties far exceeding those of conventional concrete, making it an ideal material for bridge deck joints. This project included a multi-faceted evaluation of the proprietary UHPC material, Lafarge Ductal®, to determine best practices for placing UHPC joints and to better understand their behavior. Composite modulus of rupture (MOR) specimens were tested in flexure to determine the effects of varying interface angles and levels of surface roughness on bond strength. Slant shear tests were performed on composite cylinders to provide a baseline of bond strength with no surface manipulation. Static and fatigue flexural testing was performed on three medium-scale slabs with heat cured UHPC joints to determine their flexural capacity and the effects of cyclic loading on the joint interface. The MOR specimens exceed the flexural strength of the base concrete, and most did not experience interface failure. Two slabs, tested statically in flexure, had experimental capacities exceeding the estimated capacity. The third slab, loaded cyclically, achieved 3 million cycles of a load less than the cracking load and experienced degradation in performance. It then failed at a much lower number of cycles after the load was increased. These results indicate that UHPC provides superior structural performance for slab joints and is worth studying further in future research

Does practicing hatha yoga satisfy recommendations for intensity of physical activity which improves and maintains health and cardiovascular fitness?

Background: Little is known about the metabolic and heart rate responses to a typical hatha yoga session. The purposes of this study were 1) to determine whether a typical yoga practice using various postures meets the current recommendations for levels of physical activity required to improve and maintain health and cardiovascular fitness; 2) to determine the reliability of metabolic costs of yoga across sessions; 3) to compare the metabolic costs of yoga practice to those of treadmill walking. Methods: In this observational study, 20 intermediate-to-advanced level yoga practitioners, age 31.4 ± 8.3 years, performed an exercise routine inside a human respiratory chamber (indirect calorimeter) while wearing heart rate monitors. The exercise routine consisted of 30 minutes of sitting, 56 minutes of beginner-level hatha yoga administered by video, and 10 minutes of treadmill walking at 3.2 and 4.8 kph each. Measures were mean oxygen consumption (VO2), heart rate (HR), percentage predicted maximal heart rate (%MHR), metabolic equivalents (METs), and energy expenditure (kcal). Seven subjects repeated the protocol so that measurement reliability could be established. Results: Mean values across the entire yoga session for VO2, HR, %MHR, METs, and energy/min were 0.6 L/kg/min; 93.2 beats/min; 49.4%; 2.5; and 3.2 kcal/min; respectively. Results of the ICCs (2,1) for mean values across the entire yoga session for kcal, METs, and %MHR were 0.979 and 0.973, and 0.865, respectively. Conclusion: Metabolic costs of yoga averaged across the entire session represent low levels of physical activity, are similar to walking on a treadmill at 3.2 kph, and do not meet recommendations for levels of physical activity for improving or maintaining health or cardiovascular fitness. Yoga practice incorporating sun salutation postures exceeding the minimum bout of 10 minutes may contribute some portion of sufficiently intense physical activity to improve cardio-respiratory fitness in unfit or sedentary individuals. The measurement of energy expenditure across yoga sessions is highly reliable

EVALUATION OF ULTRA-HIGH PERFORMANCE CONCRETE FOR USE IN BRIDGE CONNECTIONS AND REPAIR (FHWA-OK-21-03)

The project described in this report evaluated available proprietary ultra-high performance concrete (UHPC) materials and UHPC mix designs made with local materials for applicability to bridge joint installation and repair in Oklahoma and developed recommendations for continued usage of UHPC in bridge construction in Oklahoma. Phase 1 of the project developed a promising UHPC mix design, J3, using local materials. Two specific applications of UHPC were considered: deck slab joints and girder continuity connections. Initial investigation of deck slab joint details was conducted using small-scale flexural specimens to evaluate bond strength between UHPC and base concrete. Laboratory-scale full-depth joints were cast and tested using both the proprietary UHPC material and the OU developed J3 mix design. Laboratory scale UHPC connections for live load continuity between precast girders were also designed and tested to failure. Two different connection details were used, one representing new construction and one representing retrofit of an existing structure. A field test involving retrofit of an existing expansion joint with UHPC joint headers was conducted on a bridge identified in conjunction with ODOT and was monitored for almost three years. Phase 2 involved slab testing for a partial depth slab joint detail, examination of reinforcement bond, and durability testing of both proprietary and non-proprietary UHPC. UHPC bond to concrete substrate was also examined for different surface preparations and base concrete saturation levels. The findings of the research indicate that UHPC provides improved performance relative to conventional materials for the applications tested and the J3 mix design exhibits similar performance to proprietary UHPC.Final Report October 2016 - October 2020N