International Concrete Abstracts Portal

Hybrid cements contain a small amount of Portland cement; the rest of the binder is made up of pozzolanic or latent hydraulic admixtures. Another component is an alkaline activator. These binders, therefore, combine the advantages of alkaline activation and Portland cement. In this work, a combination of Portland cement, ground granulated blast furnace slag (GBFS), siliceous fly ash (FA), and ground recycled masonry (GRM) is chosen. The GRM mainly contains ground bricks - i.e., heat-treated clay with potential pozzolanic properties and usually about 7-8% CaCO3 from the original mortar. Sodium water glass modified with potassium hydroxide is used as an activator. Potassium ions improve the workability of the mixture and limit the efflorescence of the hardened mixture. The dose of cement was optimized, as well as the dose of the activator. Furthermore, mixtures with different GBFS or FA and GMR ratios were tested. With an optimal composition and a water-to-binder ratio of 0.50, it is possible to achieve compressive strengths between 15 and 20 MPa at the age of 28 days, with the expectation of further improvement.

The increasing demand for sustainable building products with lower carbon footprints is a huge global challenge that can hardly be faced by conventional cementitious mixtures. In this context, the use of alternative primary binders, such as hydraulic lime, should be explored. Research in this direction should aim at the development of innovative eco-friendly materials with suitable mechanical performance. For the retrofitting of masonry structures, for instance, it may be necessary to improve their mechanical properties by incorporating supplementary cementitious materials (SCMs), further reducing, at the same time, their environmental impact.

This study investigates the effects of silica fume and metakaolin included either individually or together alongside natural hydraulic lime. The mechanical performance of such binary and ternary binders has been characterized in terms of flexural and compressive strength. Moreover, scanning electron microscopy (SEM) has been used to study the microstructure of the mixtures. Finally, a preliminary investigation concerning the effect of curing time in lime-based mixtures with combined silica fume and metakaolin has been performed to investigate the possible benefits of this approach. The results highlight the superior pozzolanic efficacy of silica fume compared to metakaolin and point towards the proper dosages of SCMs to achieve optimal mechanical performance.

The 16th International Symposium on Fiber-Reinforced Polymer (FRP) Reinforcement for Concrete Structures (FRPRCS-16) was organized by ACI Committee 440 (Fiber-Reinforced Polymer Reinforcement) and held on March 23 and 24, 2024, at the ACI Spring 2024 Convention in New Orleans, LA. FRPRCS-16 gathers researchers, practitioners, owners, and manufacturers from the United States and abroad, involved in the use of FRPs as reinforcement for concrete and masonry structures, both for new construction and for strengthening and rehabilitation of existing structures. FRPRCS is the longest running conference series on the application of FRP in civil construction, commencing in Vancouver, BC, in 1993. FRPRCS has been one of the two official conference series of the International Institute for FRP in Construction (IIFC) since 2018 (the other is the CICE series). These conference series rotate between Europe, Asia, and the Americas, with alternating years between CICE and FRPRCS. The ACI convention has previously cosponsored the FRPRCS symposium in Anaheim (2017), Tampa (2011), Kansas City (2005), and Baltimore (1999). This Special Publication contains a total of 52 peer-reviewed technical manuscripts from 20 different countries from around the world. Papers are organized in the following topics: (1) FRP Bond and Anchorage in Concrete Structures; (2) Strengthening of Concrete Structures using FRP Systems; (3) FRP Materials, Properties, Tests and Standards; (4) Emerging FRP Systems and Successful Project Applications; (5) FRP-Reinforced Concrete Structures; (6) Advances in FRP Applications in Masonry Structures; (7) Seismic Resistance of FRP-Reinforced/Strengthened Concrete Structures; (8) Behavior of Prestressed Concrete Structures; (9) FRP Use in column Applications; (10) Effect of Extreme Events on FRP-Reinforced/Strengthened Structures; (11) Durability of FRP Systems; and (12) Advanced Analysis of FRP Reinforced Concrete Structures. The breadth and depth of the knowledge presented in these papers is clear evidence of the maturity of the field of composite materials in civil infrastructure. The ACI Committee 440 is witness to this evolution, with its first published ACI CODE-440.11, “Building Code Requirements for Structural Concrete with Glass Fiber Reinforced Polymer (CFRP) Bars,” published in 2022. A second code document on fiber reinforced polymer for repair and rehabilitation of concrete is under development. The publication of the sixteenth volume in the symposium series could not have occurred without the support and dedication of many individuals. The editors would like to recognize the authors who diligently submitted their original papers; the reviewers, many of them members of ACI Committee 440, who provided critical review and direction to improve these papers; ACI editorial staff who guided the publication process; and the support of the American Concrete Institute (ACI) and the International Institute for FRP in Construction (IIFC) during the many months of preparation for the Symposium.

Unreinforced masonry buildings (URM) are particularly vulnerable to local out-of-plane failure mechanisms of the walls during earthquakes. This study investigates the effectiveness of a relatively novel class of inorganic composite materials, namely Fibre Reinforced Mortars (FRM), for the out-of-plane strengthening of masonry walls. Experimental tests by using a setup to perform out-of-plane tests on masonry panels, part of an enlarged ongoing testing campaign, are presented herein. Two types of masonry walls are investigated: solid clay brick masonry walls and tuff masonry walls. The specimens are subjected to compressive axial load and out-of-plane horizontal actions according to a “four-point bending test” scheme. Two specimens are reinforced before testing with FRM in double-side configuration, while other two specimens are tested in their bare configuration. Experimental results in terms of capacity curves and deformed shapes are reported and discussed. The preliminary results attest that FRMs are effective in increasing the out-of-plane capacity of masonry walls and in postponing the activation of the out-of-plane failure mechanism.

his paper presents an experimental study on the discontinuous confinement of small-scale masonry columns using a FRCM system. The study aims to investigate the effectiveness of the FRCM in enhancing compressive strength and ductility under axial loading condition. In detail, the adopted FRCM system was composed of a cementitious matrix reinforced with PBO mesh. It was applied to the masonry columns using a discontinuous wrapping technique, which involved wrapping the FRCM material around the column in segments, leaving gaps between the segments itself.

More in deep, the experimental program included twelve specimens, ten (i.e. five couples) of which were wrapped with the PBO-FRCM system using the discontinuous wrapping technique, while the remaining two columns were left unconfined and served as the control group. The columns were measured concerning the load-displacement behavior, ultimate strength and failure mode and then compared between the FRCM-confined and unconfined columns. In particular, the amount of fiber in the vertical direction was kept constant, while the scheme of confinement was varied by both changing the strip width and spacing. In total, five different schemes of discontinuous confinement were proved. The performed research aims to contribute to the knowledge in the field of FRCM-masonry confinement, mainly focusing on the influence of the mentioned parameter.