International Concrete Abstracts Portal

The Second CANMET/ACI International Conference was held in Brazil in 1999 and showcased information on emerging high-performance concrete in Brazil and other South American countries. Over 100 papers were submitted from all over the world and were reviewed in accordance with ACI policy. Forty-five were accepted for publication in this volume. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP186

The present paper is devoted to the analysis of the behaviour of high performance concrete structures made with members reinforced with Fiber Reinforced Polymer (FRP) rebars. Models usually adopted for the evaluation of the deformability of steel reinforced concrete structures are described and their use for the analysis of FRP reinforced concrete structures is discussed. A theoretical model, developed taking into account both the real behaviour of materials and the interaction between the reinforcement and the concrete matrix is, thus, used to determine typical quantities that characterize the serviceability of reinforced concrete structures (moment-curvature and load-deflection diagrams). A large numerical investigation has been carried out in order to evidence the influence of predominating geometrical and mechanical parameters on the serviceability behaviour of FRP reinforced concrete beams. Finally, results of an experimental analysis, carried out by flexural tests on concrete beams reinforced with Aramidic Fiber Reinforced Polymer (AFRP) rebars, are described and a comparison between previsions of models and the experimental results has been made.

The results of an experimental investigation on the mechanical properties and durability of high performance concrete are presented. The concrete was produced with two types of cement, two different aggregates (shingle and granite) and addition of silica fume. The compressive and splitting tensile strength as well as the secant modulus of elasticity were evaluated on concrete having compressive strength up to 90 MPa and ages from 16 hours to 91 days. The complete stress-strain curve in compression was obtained at 28 days in a strain controlled mode. The durability tests include abrasion resistance, water permeability and carbonation depth. The results indicate that the mechanical properties investigated have different developments with respect to time. They also show expressively the effect of the different coarse additionally demonstrates significant reduction in water permeability, porosity abrasion resistance. High-performance concrete also proved to be more resistant to carbonation even under poor curing conditions, and higher CO2 concentrations.

Very-high strength concrete (>100 MPa) has been developed using different types of ultra-fine particles: silica fume, ground granulated blast furnace slag, metakaolin, and cristobalite. The effect of the type of ultra-fine particle on some engineering properties of concrete has been investigated: compressive strength, loss of workability and plastic shrinkage. The highest level of strength (120 MPa) was obtained using either 20% slag, or 10% metakaolin, in addition to cement. The workability was maintained for one hour when slag or cristobalite were presenting the mixture. The tests undertaken on plastic shrinkage pointed out that very-high strength concrete developed high plastic shrinkage, specially when pozzolans were used. The use of slag does not affect the plastic shrinkage.

The results of an experimental investigation on the water permeability of high performance concrete are presented. Several aspects were studied including different components for the concrete as well as the load history for the test specimens. The concrete was made with Brazilian Type CP V ARI cement (ASTM Type III), type different aggregates (limestone and gneiss) and silica fume. The concrete compressive strength was above 50 MPa at 28 days. For the water permeability test, the apparatus developed by Ludirdja et al. at the University of Illinois was employed. Permeability test were subjected to different load histories. In series 1, the applied load was equal to 40% of the ultimate compressive strength, while in series 2 this value was increased to 70%. The secant modulus of elasticity and the splitting tensile strength of the concretes at the start of the permeability test were also evaluated. The test results indicate clearly the effects of the load history on the value of the water permeability coefficient. As the load increases, the value of this coefficient also increases. The results also show that for high-performance concrete produced with Brazilian Type CP V ARI cement, the prescribed compressive strength may be reached in a short period of time, but the long-term water permeability coefficient seems to require a longer time to develop.