Usman Javed

The surge in production of cement due to the rapid growth of the construction industry has an adverse effect on the environment globally caused by the huge amount of carbon dioxide emission. To produce an environment-friendly concrete, this study investigated the effective contribution of silica fume on the various mechanical and durability characteristics of high-strength concrete. In this regard, the incorporation of silica fume was carried out with progressive proportions of 0, 5, 10, 15, 20, 25 and 30% by weight of cement constituting various concrete mixes – namely, CM, SF05, SF10, SF15, SF20, SF25 and SF30, respectively. The mechanical and durability properties of concrete improved with the incorporation of silica fume up to 15% replacement. However, excessive replacement of silica fume has an adverse effect on the mechanical and durability properties of cement due to the dilution effect on cement. Similarly, in terms of mechanical characteristics, the proposed 15% substitution of silica fume resulted in the highest compressive and flexural strengths with respect to those of CM. The maximum reduction in strength loss with respect to that of the control mix was 41.17 and 28.04% for sulfuric and hydrochloric acids due to the formation of a densified microstructure.

Using biomass waste as supplementary cementing material (SCM) in concrete has attracted researchers’ attention for efficient waste utilization and reducing cement demand. Sugarcane bagasse ash (SCBA) is one such example of biomass waste. It is an agricultural waste obtained when sugarcane bagasse from the sugar industry is used for power generation and disposed of in open-air dumping sites. Its waste disposal causes the generation of particulate matter, degrading air quality. In this study, the effect of processed SCBA as SCM in concrete has been investigated. The processing of the SCBA involved the removal of fibrous and carbon-containing particles by sieving followed by grinding. The SCBA was ground for 45 min until the surface area was comparable to that of cement and was then used for further characterization and incorporation into concrete. The 45 min grinding time resulted in 2.92 times higher pozzolanic reactivity of the SCBA. The SCBA was incorporated by replacing cement in different weight fractions (10%, 20%, 30%, 40%) in concrete. Test results showed that the concrete workability increased with SCBA incorporation, whereas the resulting concrete density was reduced. The results of the mechanical properties, including compressive sstrength and hardened density, were enhanced upon the cement replacement by SCBA. Concrete containing 30% SCBA can be used for structural applications as its 28 days compressive strength was 21 MPa, which complies with ACI 318-16 specifications. Concrete resistance against scaling and leaching due to adverse effects of sulfuric and hydrochloric acid considerably increased with SCBA addition and was due to microstructure densification by secondary hydrates formation as lower portlandite content was detected by thermogravimetric analysis. Hence, SCBA processing increases its reactivity, as reflected by the improved mechanical properties and greater durability of SCBA-incorporated concrete.