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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 18 Abstracts search results
July 1, 2022
E. Redaelli, M. Carsana, A. Filippi, F. Lollini
The use of recycled aggregates allows for reducing the environmental impact of concrete materials, by reducing the amount of waste and limiting the consumption of natural resources. Recycled asphalt pavement (RAP) is a granular material that comes from the milling of road pavements whose size and distribution make it suitable as aggregate for concrete. The environmental benefits of the replacement of natural aggregate with RAP need to be assessed with a better understanding of the long-term behavior of RAP concrete, considering the evolution of its performance in time and its ability to guarantee an adequate service life when exposed in operating conditions. This note presents the preliminary results of research on the effect of RAP on concrete properties. The addition of RAP aggregate affects concrete properties in a fresh and hardened state. Some parameters showed clear trends with the percentage of RAP, however, also other factors (e.g. w/c ratio and curing time) seem to play a role. Compressive strength and dynamic modulus of elasticity of RAP concrete were always lower compared to reference concrete, while the electrical resistivity did not show a clear trend. Further investigations will be carried out to clarify the role of RAP aggregate.
Andrea Filippi, Maddalena Carsana, Federica Lollini, Elena Redaelli
The milling of road pavements produces a granular material (called recycled asphalt pavement, RAP) whose size and distribution are suitable for its use as aggregate in concrete. The use of RAP as aggregate in concrete would have a twofold beneficial effect: reducing the amount of wasted asphalt and limiting the consumption of natural aggregates. In view of an assessment of the actual environmental benefits of concrete made with RAP aggregate, a thorough evaluation of its performance needs to be carried out, both on the short term (e.g., workability, shrinkage) and on the long term (e.g., resistance to aggressive environment and protection of embedded reinforcement from corrosion). Structural and mechanical properties (e.g., compressive strength, modulus of elasticity) also need to be assessed. This note presents the preliminary results of laboratory tests aimed at the characterization of RAP as aggregate to produce concrete. The characterization included analyses of size distribution by sieving, assessment of fine, chloride content, ESEM observations and XRD analyses, moisture content, and water absorption. Tests were performed on batches of RAP coming from different production plants to assess the variability and also, for comparison, on natural limestone aggregate. Results show a particle size distribution with a good replicability within the same site; all particle size fractions seem to be covered and the maximum diameter is around 21-22 mm. Regarding the microstructure of the aggregates, this is practically the same as for natural aggregates, except for the bituminous coating. The chloride content was negligible. Water absorption is higher compared to values of natural aggregates, probably because of surface dust layers and various impurities, which soak more water.
N. Klein, F. Lang-Scharli, T. Kränkel, C. Gehlen
We analyzed pervious concrete with regard to its acoustic absorption behavior. For this purpose, we cast a pervious concrete test series using different coarse aggregates varying in shape (crushed vs. rounded) or size (2-5 mm (0.08-0.20 in.)), to 8-11 mm (0.31-0.43 in.)). All test series were compacted in a gyratory compactor with variable intensities to reach an aimed total porosity of 25.0, 22.5, and 20.0 % by vol. and thus to evaluate the effect of the amount of the porosity beside the effects of aggregate shape and geometry on the acoustic absorption. Furthermore, we quantified the effect of the pervious concrete layer height on its acoustic absorption by a stepwise alternate cutting and measuring of the specimens at layer heights from 100 mm (3.94 in.) to 40 mm (1.74 in.). We used the first maximum of the absorption coefficient, its frequency, and the sound wave propagation speed in the porous material to evaluate the acoustic absorption. In general, a higher porosity, bigger grain size, the use of rounded aggregates, and higher cylinder height increases the acoustic absorption. A characteristic pore structure factor was found, which allows a prediction of the frequency in dependence of the cylinder height.
September 30, 2019
Anol Mukhopadhyay and Xijun Shi
Potential issues associated with depletion of good aggregate sources and management of excess RAP stockpiles increasingly motivate use of RAP in PCC as a coarse aggregate replacement. Texas has shown great interest in disposing excess RAP stockpiles and a systematic study on using RAP in PCC for Texas pavement applications was conducted by the authors recently. This paper provides a concise summary of the findings from this study. The major conclusions are (1) PCC mixture with dense aggregate gradation can be achieved by adding coarse
RAP with adequate intermediate sized particles, which offers better overall performance in terms of workability and mechanical properties, (2) RAP-PCC with coarse RAP replacement up to 40% showed considerable reduction for modulus of rupture. Asphalt cohesive failure (crack passing
through the asphalt layer) was found to be the main mechanism responsible for the strength reductions, (3) the addition of allowable amounts of RAP into PCC provides equivalent durability performance relative to plain PCC, and (4) constructing pavements with RAP-PCC yields economic, environmental and social benefits.
March 17, 2017
The ACI Committee 544 on fibre-reinforced concrete (FRC) has been involved in development and dissemination of technical information for nearly a half century. A key advantage in using FRC is the reduction in construction time compared to the traditional reinforcing bars or welded wire mesh. Application areas for FRC have extended to areas where high early strength and ductility are important and include pavement, shotcrete and structures such as bridge deck slabs, or rock slide stabilization. In these cases, the material properties must
be measured using experimental test data obtained from an experimental program. Test results must be analysed in order to obtain effective stress strain responses that can be incorporated in analytical, or computer simulation. A list of examples including wall panels, hydraulic structures, airport pavements, and industrial floor overlays are described. To maintain integrity without collapse, such structural elements need to be designed with proper material models and analysis tools discussed.
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