International Concrete Abstracts Portal

There is a lack of comprehensive guidelines for the use of fiber-reinforced polymer (FRP) dowels in concrete pavement construction. In light of this, NEx: An ACI Center of Excellence for Nonmetallic Building Materials has announced a newly published document SG23.03 (25): NEx Guideline: FRP Dowels in Concrete Pavements.

Increasing use of deicing chemicals can pose a great risk of premature failure of concrete infrastructure such as pavements and bridge decks. This article discusses an immersion study of ordinary portland cement and high-volume fly ash mortars in MgCl₂ solution under room temperature and its influence on mechanical properties and transport property.

To support a rapid integration of sustainability principles into paving concrete practice, this study provides a closer look into readily implementable cement and concrete decarbonization strategies. To do so, this study relies on combined stakeholder involvement, quantitative analysis using Life Cycle Assessment (LCA), and the state-of-the-practice in the US paving concrete industry to understand merits of each solution. The results indicate that concrete mix design optimization is a promising, yet not widely applied solution that can reduce costs, enhance durability, and provide average carbon emissions savings of 14 percent. Use of supplementary cementitious materials (SCM) is another solution with multiple benefits, however, the use of SCM is already widely implemented across the USA. Industry-wide improvement in cement carbon footprint due to energy efficiency can provide additional savings of up to 10 percent. Quantifying the environmental footprint of concrete is critical to inform decision-making and enable more sustainable outcomes.

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.

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.