Multi-Scale Physical–Mechanical Characterization of Eco-Self-Compacting Concrete Incorporating Recycled Aggregates and Waste Fibers

In response to the imperative for ecological transition within the construction sector, developing high-performance and durable eco-materials represents a major engineering challenge. The characterization of eco-friendly self-compacting concrete produced from industrial by-products requires establishing reliable constitutive relationships between fundamental physical properties and mechanical performance. The primary objective of this study is to quantify these correlations in order to optimize on-site quality control and reduce reliance on destructive mechanical testing during eco-design phases.

A multi-scale experimental methodology was conducted on three eco-material families incorporating recycled aggregates, waste fiber reinforcements, and local low-carbon binders. Physical characterization was based on pycnometry (density determination), the vacuum saturation method (effective porosity evaluation), and 24-hour water immersion tests (water absorption capacity). Regarding mechanical performance, Unconfined Compressive Strength and Splitting Tensile Strength tests were conducted after 28 and 180 days of curing. Concurrently, non-destructive Ultrasonic Pulse Velocity measurements were used as an indirect method to establish a connection between the internal physical structure and the elastic modulus.

The experimental results indicate a negative correlation between compressive strength and porosity across all tested specimens. Specifically, a reduction of approximately 5% in total porosity translates to an increase in compressive strength of approximately 20%. Elevated water absorption was identified as the primary cause of reduced durability. Material bulk density also proved to be a reliable predictive indicator of shear strength in these eco-materials. These correlations establish a simple and effective methodological framework for in situ quality control of physical and mechanical performance.

This research provides an extensive dataset on green alternatives to conventional materials. By precisely elucidating the relationships between physical and mechanical properties, this study mitigates reliance on destructive testing during preliminary material selection, thereby fostering the large-scale integration of sustainable materials.