Effect of mechanical activation of fly ash added to Moroccan Portland cement

Abstract

Nowadays, the cement industry is the largest emitter of CO2. In 2015, cement production accounts for roughly 8% of global CO2 emissions. In order to reduce this impact, cement plants are working on alternative solutions, for instance, producing cement by adding additives like fly ash known for reducing the emissions of CO2 and minimizing production costs. The thermal power stations in Morocco produce more than 500 000 tons per year. For ecological and sustainable development reasons, it is desirable to recycle these quantities according to beneficial methods to their addition in the cement. This study aims to investigate the influence of grinding fly ash on the physico-chemical and mechanical properties of fly ash blended CPJ45 cement. The addition of the fly ash particles to the grinder leads respectively to the breakage of the particles and to reduce the agglomeration effect in the balls of cement grinder. Fly ash milling was found to improve particles fineness, and increase the silica and alumina content in the cement. Furthermore, milled fly ash blended cements show higher compressive strength compared to unmilled fly ash blended cements, due to improved fly ash reactivity through their mechanical activation.

The Effect of Mechanical Activation of Fly Ash on Cement-Based Materials Hydration and Hardened State Properties

“…The data in Table 2 show that the amount of SiO 2 and Al 2 O 3 in the AFA composition increased by about 1-1.5% after mechanical activation. Other researchers [43][44][45] also noticed such an effect. The mechanical activation process causes the fragmentation of coarse particles, increases the specific surface area, and increases the amount of Si and Al in the fly ash.…”

“…The reactivity of fly ash varies with median particle size and increases rapidly when the particle size is reduced to less than 7 µm, resulting in the faster creation of a hydration product. Additional information about fly ash milling is presented in the research of [44,45]. The fly ash was milled together with cement because the addition of the fly ash can decrease the agglomeration effect in the milling device.…”

Effects of Wet Separated and High Speed Milling Fly Ash Added in High Volume to Cementitious Materials

“…Decrease in crystal state, gross distortion and enhanced reactivity of fly ash occurred due to vibratory ring mechanical milling, whereas enhanced reactivity is less prominent for planetary and conventional ball mills [11]. Fly ash milling was found to improve particle fineness, to increase the silica and alumina content in the cement, milled fly ash blended cements show higher compressive strength compared to un-milled fly ash blended cements, due to improved fly ash reactivity through their mechanical activation [12]. Higher pozzolanic activity for fly ash was achieved for the same specific surface area using high-speed pin mill with two counter rotors, and this type of mill can be a promising means of improving its properties via grinding and mechanical activation [13].…”