INFLUENCE OF NANO-SILICA AND GROUND GRANULATED BLAST FURNACE SLAG ON CEMENT USING STATISTICAL DESIGN OF EXPERIMENT by Arvinder Singh
Cement and concrete have been subjected to modification in earlier research works for the enhancement in its properties. However investigating the properties of concrete at nano-level is a comparatively new concept and nanotechnology can be applied to Civil Engineering by various concepts including addition of nanomaterials like Nano-Silica. On the other hand, use of waste materials as a replacement of cement is the need of the hour and the waste materials like furnace slag does possess cementetious character. This study was performed to study the effect of addition of Nano-Silica (Nano-SiO2) (0 - 3% by weight of cement) and waste material Ground Granulated Blast Furnace Slag (GGBS) (25 – 65% by weight of cement) on the physical properties of cement like Standard Consistency, Setting times, Compressive Strength at the ages of 7, 28 days. For structuring and analyzing the experiment, the Factorial design approach was adopted. From the study it was observed that addition of even small amount of Nano-Silica can drastically change the characteristics of cement like increase in the early age strength by 15% for 3% Nano-Silica replacement due to the acceleration of hydration of cement, but it also caused the increase in consistency limit from 28% to 31%. The setting times were also drastically reduced with addition of Nano-Silica. GGBS addition however resulted in slowed the hydration reaction, decrease in strength gain and water requirement due to its low hydraulic reactivity. However, by adding GGBS alongwith Nano-Silica it restricted the drastic drop in setting times of cement and also resulted in increased compressive strength by 11% at 2% Nano-Silica and 45% GGBS replacement due to the consumption of Ca(OH)2 and formation of additional C-S-H by both Nano-Silica and GGBS. Beyond the range 2% Nano-Silica and 45% GGBS the strength reduction was noticed probably due the decrease in the available free lime concentration at high concentrations of Nano-Silica and GGBS. The analysis of above experiment was carried out using factorial design of experiment, ANOVA was adopted for analysis of the 28-day Compressive strength which gave the result that Nano-Silica had more profound effect on strength of cement. Regression analysis was adopted to derive a relationship between the compressive strength of cement and different proportions of Nano-Silica and GGBS.