Restructuring the Basic Design of Several Accelerator-Based Concrete Mixes by Integrating Superplasticizers

The increasing demand for infrastructure, the need to consolidate aging structures, and the effects of climate change imply the replacement or improvement of traditional concrete. This study investigates three accelerators and their mixtures (Ca(NO₃)₂·4H₂O, Al₂(SO₄)₃·18H₂O, and Na₂S₂O₃·5H₂O) (series I) and their counterparts with superplasticizers (Dynamon SR41) (series II) as additives in standard concrete to improve its functionality. The standard concrete and new concrete mixes were analyzed using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and tests for water absorption, bulk density, and compressive strength. XRD analysis showed that all concrete mixes had similar structures composed of quartz, portlandite, larnite, calcium silicate, ettringite, albite, and muscovite in varying proportions. Their microstructures, as shown by SEM images, revealed the presence of ettringite, portlandite, and C-S-H gel at high magnification (1-5 kx). The addition of the superplasticizer remodeled the surface of the concrete mix, reducing the pore radius and increasing its compaction. These changes helped to reduce its bulk density while increasing the compressive strength. The results showed that all the concrete mixtures are similar to the standard concrete and can replace it for better functionality, but Na₂S₂O₃·5H₂O with superplasticizer concrete mixture had the higher compressive strength, supplying additional benefits.