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.

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.

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.

Pavement subgrade is an in-situ material upon which the pavement structure is constructed. A soil with a high plasticity index will experience high shrinkage and swell depending upon its moisture content with detrimental impacts on its supported pavement structure. Removing and replacing the weak soil with better-quality soil is an alternative to stabilization of poor subgrade soil and may be a very expensive solution, typically for large road networks. Secondly, stabilization of weak soil -subgrade using conventional cement may not be sustainable due to its high CO₂ footprint. The feasibility of this non-conventional method using blended geopolymer binder for stabilization of weak subgrade soil was investigated compared to the conventional cement stabilization method. Laboratory testing of design mixes included unconfined compression test, maximum dry density, CBR and shrink & swell testing determining its feasibility and optimum extent. This research paper will present the findings on the effectiveness of blended geopolymer (fly ash and slag) as an alternative to conventional cement-based soil stabilizers for weak subgrade and its sustainability potential.

Scrap tyres are one of the most serious wastes that are landfilled with small percentages. Recycled scrap tyres are being used in different domains of industry because they are notdegradable. The experimental work focused on mechanical properties and durability indicators of self-compacting sand concretes blended with recycled rubber. Such modified concretes comprised 5, 10, 15 and 20% of rubber fine powder (RFP) and coarse particles (RCP) as partial substitutions of natural sand and aggregates. To shed light on physical and mechanical properties rubber particles effects, ordinary vibrated and self-compacting as well as self-compacting sand concretes (SCSCs) were characterised. Special attention was given to compression and bending performances of SCSCs. Identification of two durability indicators — water porosity and density — was assessed, according to AFGC specifications. Experimental findings enhanced previous literature reported statements and demonstrated that use of rubber particles as substitutes improved performances of elaborated SCSCs and produced eco-friendly materials that are appropriate for large surface applications such as pavements and terraces as well as civil engineering constructions.