International Concrete Abstracts Portal

NEU: An ACI Center of Excellence for Carbon Neutral Concrete introduced its new third-party Validation/Verification Program for the cement and concrete industries. NEU’s Program provides third party validation or verification of the environmental claims of both existing and innovative new products and technologies associated with reduced carbon cement, concrete production, and concrete products following International Organization for Standardization (ISO) standards.

Dean Frank, Executive Director of NEU: An ACI Center of Excellence for Carbon Neutral Concrete, participated in the National Institute of Standards and Technology (NIST) Low Carbon Cements and Concretes Consortium second annual in-person meeting in Frederick, MD, USA. Frank also attended the White House Office of Science and Technology Policy (OSTP) Concrete Innovation Summit at the Eisenhower Executive Office Building on the White House grounds.

An emerging strategy to reduce the concrete industry’s carbon emissions is the use of ternary binders prepared with Portland cement, limestone filler, and supplementary cementitious materials. However, in most cement standards, the limestone content permitted in these ternary binders limits their potential to reduce these emissions. In this study, concrete was prepared with a ternary blended cement containing Portland cement, ground granulated blast furnace slag, and limestone filler at a filler content significantly higher than is currently permitted in EN 197. To achieve the desired mechanical and durability properties when employing a high filler content, a significant reduction in the water-binder ratio is required. Thus, the primary challenge for concrete formulation with such a binder is achieving the required rheological properties at a water content that allows the concrete to meet its strength and durability targets. Here, the rheological properties of a high filler—low water concrete were investigated at the concrete scale via rotational rheometry and compared with a more conventional ready-mix concrete. The results show that it is possible to produce concrete consistent with the workability demands of the ready-mix concrete industry in France with a binder intensity of less than 3.0 (kg/m³)/MPa [0.035 (lbs/yd³)/psi].

Fiber reinforced polymers (FRP) are commonly used to seismically retrofit concrete structural walls. Limited design guidance for the seismic application of FRP strengthening is currently available to designers in guidelines such as ACI PRC-440.2-17 or standards like ASCE/SEI 41-17. This paper presents the description and results of an experimental effort to investigate the effectiveness of FRP retrofitted concrete walls. The specimen wall thickness was either 6 in or 12 in, which represents a typical range of wall thickness seen in older buildings. To better reflect the most common applications seen in the industry, the walls were retrofitted with FRP, and anchored with fiber anchors only on one side of the wall. The study demonstrates that the effectiveness of FRP is reduced as the wall thickness increases and that the FRP must be anchored to the wall for any tangible benefit. The results are used to assess the current provisions in ACI PRC-440.2-17 and ASCE/SEI 41-17. It is apparent that additional testing is required to better understand the complexities involved in the FRP strengthening of shear walls and such testing is scheduled for the near future.

The seismic performance of reinforced concrete (RC) structures relies on their ability to dissipate earthquake-induced energy through hysteric behavior. Ductility, energy dissipation, and viscous damping are commonly used as performance indicators for steel-RC seismic force-resisting systems (SFRSs). However, while several previous studies have proposed energy-based indices to assess energy dissipation and damping of steel-RC SFRSs, there is a lack of research on fiber-reinforced polymer (FRP)-RC structures. This study examines the applicability of the existing energy dissipation and damping models developed for steel-RC columns to glass FRP (GFRP)-RC ones, where the relationships between energy indices and equivalent viscous damping versus displacement ductility were analyzed for GFRP-RC circular columns from the literature. In addition, prediction models were derived to estimate energy dissipation, viscous damping, and stiffness degradation of such types of columns. It was concluded that similar lower limit values for energy-based ductility parameters of steel-RC columns can be applied to GFRP-RC circular columns, whereas the minimum value and analytical models for the equivalent viscous damping ratio developed for steel-RC columns are not applicable. The derived models for energy indices, viscous damping, and stiffness degradation had an R2 factor of up to 0.99, 0.7, and 0.83, respectively. These findings contribute to the development of seismic design provisions for GFRP-RC structures, addressing the limitations in current codes and standards.