This paper presents pedagogical techniques used to teach fresh and hardened properties of concrete. Fresh properties of concrete include the evaluation of slump, unit weight, and air content. The hardened properties of concrete include compressive and tensile strengths. Students typically have little to no prior experience working with concrete. Since concrete structures date back to Ancient Rome, many students assume concrete is a basic material that has not changed in centuries, and they do not view concrete as an engineered material. Therefore, their understanding of how concrete is an engineered material and its use is essential. This paper focuses on how both fresh and hardened concrete properties are taught in the classroom to best introduce students to concrete as an engineered material. The pedagogical methods focus on engaging students using experiential education through hands-on laboratory activities, projects, and game-based learning activities. Examples of the pedagogical approaches are presented herein, and they are supported by lessons learned by the authors based on their experience implementing these methods in the classroom. two environmental conditions, sustained elevated temperatures (ST) and freeze-thaw (FT) cycles. The concrete cylinders were wrapped with a single layer of GFRP and CFRP wrap. GFRP wraps improved concrete strength by up to 30% and ductility in excess of 600% for ambient condition specimens, while the enhancements in strength and ductility under the same conditions by CFRP wraps were about 70% and 700%, respectively. The strength enhancements were reduced severely for specimens tested under ST protocol beyond the glass transition temperature (Tg) with a minor reduction in ductility enhancement. On the other hand, freeze-thaw conditioning showed minimal effect on strength and ductility enhancements provided by the FRP wraps. The current and past findings were then used to suggest environmental reduction factors for the design of FRP wraps. A comparison of these factors with ACI 440.2R-17 showed that environmental factors suggested by the ACI code were not applicable at temperatures beyond Tg.

Concrete continues to be the most widely used material in the world, second only to water. Concrete is used in most civil infrastructure systems, but it often remains inadequately understood by the profession. For civil engineers to adapt to a world requiring ever-increasing efficiency, durability, and sustainability, and in which novel material formulations and products are introduced monthly, engineers must be able to make decisions as to the acceptability of these materials, and their effect on the performance of civil infrastructure. Essential to that ability is students’ understanding of the basics of cement hydration and its relationship to property development in the fresh and hardened concrete state. Towards that goal, this paper presents the basics of cement hydration, resources for learning more about the subject, and approaches to transferring knowledge to undergraduate-level students, through both lecture- and lab-based activities. Topics addressed include prioritization of topics for undergraduate civil engineering students to learn with regards to cement hydration processes, approaches to effective teaching of these topics including active learning in the classroom and laboratory, as well as knowledge exchange strategies, assessment techniques, and lessons learned from past experiences teaching these topics.

With the aging and deterioration of infrastructure, the need for repair, strengthening, and rehabilitation of existing structures continues to increase. Climate change makes extending the service life of our infrastructure critical since any demolition and new construction will trigger substantial amounts of carbon emissions. Research related to repairing and strengthening existing infrastructure is seeing major developments as new green materials and technologies become available. Improved assessment and retrofit of deficient structures, and performance-based design of new structures are also in high demand. Despite the progress, there are many challenges yet to be addressed. The main objective of this Special Publication is to present results from recent research studies (experimental/numerical/analytical) on the retrofit and repair of structural elements along with the assessment, analysis, and design of structures. Several of these papers were presented at the ACI Fall Convention “Seismic Repair/Retrofit/Strengthening of Bridges at the Element or System Level: Parts 1 and 2.” The presented studies cover various aspects of structural retrofitting and strengthening techniques including the use of rubberized engineered cementitious composite for enhancing the properties of lightweight concrete elements, high-performance concrete jacketing to strengthen reinforced concrete piers/columns, and the behavior of fiber-reinforced-polymer-wrapped concrete cylinders under different environmental conditions. Additionally, the research explores the behavior of concrete-filled FRP tubes under axial compression, innovative bridge retrofit technologies, and retrofit techniques for deficient reinforced concrete columns. There is also a focus on evaluating the seismic response of retrofitted structures, designing guidelines for seismic retrofitting using tension-hardening fiber-reinforced concrete, strengthening unreinforced masonry walls with ferrocement overlays, and developing seismically resilient concrete piers reinforced with titanium alloy bars. The seismic response of a retrofitted curved bridge was also presented where elastomeric bearings of the as-built bridge were replaced by high damping rubber bearings as a part of the seismic retrofit. Recommendations for nonlinear finite element analysis of reinforced concrete columns under seismic loading are also presented to simulate their behavior up to collapse. Overall, the presented studies in this Special Publication demonstrate the potential of new materials, methods, and technologies to improve the performance of various structural elements under different loading conditions, including seismic and environmental loads. These studies are expected to help our practitioners and researchers not only develop more effective and sustainable methods for repairing and strengthening of structures but also improve their analysis and design skills.

This research investigates the High Performance Concrete (HPC) jacketing method to strengthen reinforced circular concrete piers/columns. Four different types of HPC jackets such as Self-Consolidating Concrete (SCC), Engineered Cementitious Composites (ECC) and two types of Ultra-High Performance Concrete (UHPC) with three jacket thicknesses of 25 mm, 38 mm and 51 mm, with same reinforcement configuration were used to strengthen reinforced SCC core piers and analyze behavior. Thirteen pier specimens were tested to failure under concentric axial load applied through the SCC core. Test results indicated performance enhancement of piers strengthened with UHPC and ECC jackets, which not only prevented brittle failure but also improved the ductility and energy absorbing capacity by achieving a superior ultimate axial load capacity increase by more than 90% with a jacket thickness of 33% of the core diameter. Existing Code and analytical equations with reduction factors can be used for predicting axial load capacity of the strengthened piers/columns but choice of equations should be based on types of jacket concrete to ensure safe design.

The use of Titanium Alloy Bars (TiABs) for flexural and transverse reinforcing in new bridge piers located in seismic zones aims to incorporate both durability and seismic resiliency. TiABs offer advantages such as: higher strength, good ductility, excellent durability, and enhanced fatigue-resistance compared to traditional reinforcing bars. The research focuses on the application of TiABs in construction of new bridges located in seismic and corrosive environments. Application of TiABs in bridge piers increases service life, reduces rebar congestion, yields to lower overstrength factor, and limits residual displacement following an earthquake. An approximately 1/3rd scale bridge pier reinforced with TiABs rebars and spirals is tested under quasi-static cyclic loading protocol to investigate seismic performance. The performance of the pier was compared against an equivalent pier reinforced with normal steel rebars and spirals. Results from testing suggested enhanced performance of a pier reinforced with TiABs in terms of reducing rebar congestion, ductility, and residual displacement following a seismic event. The structural performance and durability of bridge piers reinforced with TiABs is not compromised in moderate earthquakes as smaller flexural cracks that are more likely to appear in the plastic hinge zones are not a major concern for this pier.