Sixty percent of the nation's highly toxic and radioactive mixed wastes are stored at Hanford in 177 deteriorating underground storage tanks. To close or remove these storage tanks from service and place them in a condition that is protective of human health and the environment, the tanks must be physically stabilized to prevent subsidence once wastes have been retrieved. Remaining residual liquid waste in the tanks that cannot be removed must be solidified and the solid wastes encapsulated to meet the Nuclear Regulatory Commission, Department of Energy, Environmental Protection Agency, and the State of Washington requirements. The Department of Energy has developed cementitious flowable concretes to restrict access and provide chemical stabilization for radionuclides. Formulation, laboratory, and field testing for application at Hanford began with flowable, self-leveling structural and non-structural fills. A slump flow equal to or greater than 610 mm, 0% bleed water, and 0.1% (by volume) shrinkage measurements were key parameters guiding reformulation efforts that resulted in highly flowable, self-consolidating concretes that met Hanford 241-C Tank closure short- and long-term regulatory and engineering performance requirements.

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.

In past recent years, high-performance fiber-reinforced concretes (HPFRCs) have been studied by researchers and practitioners for applications in the construction industry. Due to the characteristics of the different mixtures, these materials appear to fulfill a large wide of requirements in structural concrete applications. Different authors have investigated the behavior of such materials, by observing that the contribution of fibers may strongly increase the mechanical properties of plain concrete. This paper reports research on very high-performance concrete (VHPC) reinforced with polymeric fibers and having self-consolidating concrete (SCC) features. A possible application of the studied materials is referred to as panel elements used as building façades. A special concrete mixture has been studied, thus the compressive strength had a target of 120 MPa (17.4 ksi) after 28 days. Flexural tests of notched beams were conducted according to EN 14651. The results obtained were used to implement a numerical model of the VHPFRC panel into two different FEA software (Abaqus & Midas FEA) for the simulation of impact resistance and structural response under UDL (uniformly distributed loading). Results obtained from the analysis showed that the addition of short fibers allows obtaining a higher target of mechanical properties concerning plain concrete, allowing possible new applications of panels without internal traditional reinforcement and reduced thickness.

Speed of production of units/structural elements and efficient use of resources are key driving forces in the precast/prestressed concrete industry and these factors significantly influence the concrete mixtures used by precast producers. For example, the production efficiencies provided by self-consolidating concrete (SCC) led to its rapid and widespread adoption in the precast industry. The development of newer high-performance concretes, such as ultra-high-performance concrete (UHPC), a continued shortage of skilled labor and societal demands with respect to sustainable concrete construction have increased the need for innovative concreting materials, in particular, chemical admixtures to address operational issues regarding concrete mixtures. Some of these issues include mixing time, flowability and flow retention, a high-quality surface finish, and very high-early strength development. In this paper, the authors present and discuss the use of innovative admixtures to address some of these performance issues; specifically, new high-range water-reducing admixtures that, respectively, provide fast wet-out of binder materials and rheology modification, nanotechnology-based strength-enhancing admixtures and a novel workability-retaining admixture.

The inclusion of rubber in concrete mixtures improved the impact resistance but negatively affected the strength and fresh properties of self-consolidating concrete (SCC). The objective of this investigation was to optimize the balance between the improved impact resistance and the reductions in the strength and fresh properties of rubberized SCC mixtures. This investigation evaluated and assessed the type/size and percentage of rubber needed to develop successful SCC mixtures with maximized impact strength and minimized reductions in strength. The studied variables were the type/size of rubber used (crumb rubber (CR) and two sizes of powder rubbers), percentage of rubber (0%, 15%, 25%, 30%, 35%, and 40%), type of concrete (SCC and vibrated concrete), and the use of fibers in the mixture. Because of the fresh properties restrictions of SCC, it was only possible to develop rubberized SCC with up to 25%, 30%, and 35% CR, powder rubber 40/80, and powder rubber 140, respectively. With the absence of fresh properties restrictions of SCC, it was possible to develop vibrated rubberized concrete with up to 40% of any type of rubber. Using higher percentages of rubber in vibrated rubberized concrete dropped the compressive strength to less than 25 MPa (3.63 ksi). The results also indicated that despite the slight improvement in the fresh properties and strength of mixtures with powder rubbers compared to mixtures with CR, mixtures with CR showed significantly higher improvements in the impact resistance.