International Concrete Abstracts Portal

Editors: Corina-Maria Aldea and Mahmut Ekenel

This CD contains 8 papers from sessions sponsored by ACI technical committees 544, 549, and 130 at the Fall 2012 ACI Convention in Toronto and two technical sessions at the Fall 2013 ACI Convention in Phoenix. The topics of the papers cover sustainability aspects of using fiber reinforced concrete ranging from durability and interface mechanisms of natural fiber reinforced concrete (FRC), evaluation of eco-mechanical performance of FRC, reducing carbon dioxide emissions of concrete, as well as applications of fiber reinforcement for self-consolidating concrete, bridge link slabs, extruded prefabricated elements, slab systems and fabric-reinforced cementitious matrix systems for strengthening unreinforced masonry walls.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-299

PrimeComposite, a steel fiber reinforced concrete (SFRC) containing proprietary additives to control hygral shrinkage, provides significant reductions in CO2 emissions per square meter and improved performance over traditional slab on grade systems. This paper describes the development of the PrimeComposite system including the structural design approach, which is based upon full-scale mechanical testing results presented here. A typical PrimeComposite slabs on grade is 10 cm thick with single-casting (jointless) areas of up to 6500 m2. At this thickness, rack system loads of 140 kN (back-to-back leg loads) are safely supported.

Masonry as a building technology meets many of the attributes of sustainable construction, thus an economical alternative to demolish-rebuild existing deficient masonry structures is to retrofit them with novel strengthening systems. Current retrofit techniques used to improve flexural capacity of un-reinforced masonry (URM) walls include both internal and external reinforcement with common materials, namely: steel bars, plates, and most recently fiber-reinforced polymers (FRPs). However, significant margins exist to advance these rehabilitation systems by addressing economic, technological, and environmental issues. This paper investigates the effectiveness of strengthening URM walls using carbon fabric-reinforced cementitious matrix (FRCM) as a technique to enhance pseudo-ductility and flexural capacity. The paper reports on the results obtained by testing a total of 18 masonry walls made of clay bricks and concrete blocks strengthened with two different FRCM schemes (one and four fabrics) subjected to uniformly distributed out-of-plane loading were tested. Experimental data from other research programs using FRP system are also presented to show that when normalized flexural capacity is related to a calibrated reinforcement ratio, the two technologies provide similar enhancements.

This paper discusses the effect of discrete pitch-based carbon fibers on the fresh and mechanical properties of self-consolidating concrete. A total of 5 non-air entrained carbon fiber reinforced self-consolidating concrete (CFRSCC) mixtures were produced incorporating fiber volume of 0%, 0.25%, 0.5%, 0.75% and 1% carbon fibers; the water-to-binder ratio (w/b) was 0.35. The fresh properties (filling ability, passing ability, and segregation) and mechanical properties (compressive strength, splitting tensile strength, modulus of rupture and toughness) of the concrete mixtures were determined. The test results revealed that at increasing amount of volume of carbon fibers decreased the filling ability and passing ability of concrete increased. The compressive strength decreased as the volume of carbon fibers increased. However, as the carbon fiber content increased the splitting tensile strength increased. Modulus of rupture and toughness of CFRSCC mixtures also increased as the volume of carbon fibers increased. The results show that it is possible to develop good crack resistant and sustainable CFRSCC mixtures for concrete structures.

The durability performance and interface transition zone of natural fiber reinforced concrete has always been a major concern. Natural fibers due to its hydrophilic nature present a high volume variation which may cause degradation in the fiber-matrix interface. Furthermore, natural FRC may undergo an enhanced aging process, while submitted to a humid environment during which they may suffer a reduction in ultimate strength and toughness. This paper presents how the use of a matrix with low content of calcium hydroxide can mitigate the embrittlement process of natural fibers. The durability performance of the composite systems is examined and the mechanisms for the significant delay in the fiber degradation when the total amount of calcium hydroxide is reduced from the matrix discussed. Furthermore, it is shown how the repeated wetting and drying cycles affects the fiber-matrix interface. Pull-out tests were performed in sisal fiber cement composite systems to study the mechanisms that influence the fiber-matrix bond. The results showed that the use of a matrix with low amount of calcium hydroxide improved the composite durability and that the wetting and drying process reduced the water absorption capacity of the fiber and increased the fiber-matrix bond.