A study on the effective utilization of ultrafine fly ash and silica fume content in high-performance concrete through an experimental approach.

Conventional cement production is a major source of CO emissions. As a result, there is an increasing emphasis on finding sustainable alternatives for cement and their appropriate proportion in concrete. This investigation explores the optimization of supplementary cementitious materials (SCM) like ultrafine fly ash (UFFA) and silica fume (SF) content in high-performance concrete (HPC). The study includes the production of binary and ternary concrete mixes by replacing Portland cement with UFFA and SF at 0, 5, 10, and 15 %. A total of 16 mixes were prepared and evaluated in three stages. The first stage involved assessing the mechanical properties using compressive strength test and non-destructive test (NDT) results at various intervals. The second stage included durability tests, such as water absorption, volume of voids, and water permeability tests. In the third stage, characterization studies like XRD, TGA, and FTIR were conducted on the finalized mixes at 28 and 90 day intervals to find the optimum mix. The NDT findings revealed that all HPC mixes had superior quality, with a velocity of more than 5 km/s. From the test results, the ternary mix U10S15 exhibited superior compressive strengths of 104.28 MPa at 90 days of curing. The durability test results also demonstrated that the blend U10S15 showed a lower water absorption of 1.26 %, indicating a 44.9 % reduction in water absorption with extended curing. The FTIR and TGA analysis of HPC mixes demonstrated that blending the optimal amounts of UFFA and SF results in a dense microstructure. The mixture U10S15 exhibits a considerable peak shift from 950 to 980 cm⁻. XRD peaks confirmed the presence of extra hydration peaks in blended specimens at 28° of 2θ. The optimized HPC mix containing 10 % UFFA and 15 % SF (U10S15) is appropriate for water-retaining structures due to its high strength, lower permeability, and higher particle packing effect.