The synergistic effect of secondary raw materials and nano additive on the properties of cement matrix

Abstract

The purpose of the research presented in this paper was to analyse the synergistic effect of nano SiO2 (NS), fluidized catalytic cracking catalyst waste (FCCCw) and calcinated at 700oC temperature paper sludge waste (PSw) on the properties the cement matrix. Nano materials are known to reduce voids between cement particles, accelerate cement hydration, and increase the strength of cement matrix. A certain amount of FCCCw and PSw in the cement mix also accelerates cement hydration and increase the compressive strength of the system, but it is important to analyse the synergistic effect of these materials on the properties of cement matrix. The results showed that both waste materials are active pozzolanic additives. The optimal quantities in terms of positive effect on the cement matrix are 10% of FCCCw and 2.5% of PSw. The paper presents the results of XRD analysis, density, ultrasonic pulse velocity and compressive strength tests with hardened cement paste. A 22% increase in compressive strength compared to the control specimen was observed in specimens where 10% of cement was replaced by FCCCw and where NS was additionally added. The replacement of cement by 2.5% of PSw increases the compressive strength about 7%. Moreover, the compressive strength of specimens containing 10% of FCCCw, 2.5% of PSw and NS increases even though the content of cement is reduced. Hardened cement paste specimens containing FCCCw, PSw, and NS have better density and ultrasonic pulse velocity values. XRD analysis showed that a combination of FCCCw, PSw, and NS added to the cement mix increases the amount of calcium hydrosilicates formed, reduces the amount of free portlandite and unreacted cement minerals (allite and belite).