US EPA

7261781 

Journal Article 

HYDRATION AND MECHANICAL PROPERTIES OF REACTIVE MAGNESIA AND SODIUM CARBONATE-ACTIVATED FLY ASH/SLAG PASTE BLENDS 

Abdalqader, AF; Al-Tabbaa, A; , 

2014 

R I L E M PUBLICATIONS 

BAGNEUX 

269-280 

WOS:000360467500026 

The cement and concrete industries currently face increasing pressures to meet the requirements of sustainability as they are responsible for similar to 5-10% of man-made CO2 emissions. Initiatives to minimise the use of Portland cement (PC), by increasing the use of industrial by-products and the developments of alternative cements are on-going on a global scale. A system of alkali-activated fly ash (FA)/slag (AAFS) mixtures as a clinkerless cement was studied. The activation of the FA/slag paste mixes with different dosages of Na2CO3, as a relatively sustainable activator, was investigated and the effect of incorporating various proportions of reactive magnesia (MgO), for enhanced strength and reduced shrinkage, was also examined. Mechanical, mineralogical, and microstructural characterisation of the cement pastes was carried out using the unconfined compressive strength, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. It was found that activating FA/slag mixtures with Na2CO3 generally increased the strength with time, and with significant increase as the activator dosage increased. At early ages, the mixes activated with 10% Na2CO3 developed comparable or better strengths to the reference mix of 70% slag and 30% PC. Additionally, using reactive MgO in the mixes also enhanced the strength at all ages. The hydration products were mainly C-S-H gel, of low-crystallinity and rich in Al and may have included Na in its structure, and hydrotalcite-like phases. 

Shi, C; Shen, X; 

2nd International Conference on Advances in Chemically-Activated Materials (CAM-China) 

Changsha, PEOPLES R CHINA