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Corrosion performance of the reinforcement was dramatically affected by chemical compositions of pore solution in alkali-activated fly ash. In this study, the electrochemical behavior and surface properties of reinforcement were characterized in chloride-contaminated simulated alkali-activated fly ash pore (SAFP) solution. The results indicated that due to the high alkalinity and formation of zeolite-like adsorption layer (about 20 nm), the reinforcement was still in passive state and exhibited high corrosion resistance in chloride-contaminated SAFP solution. However, the protective effect of passivation film (consisted of mainly FeOOH outer film and FeO inner film) and corrosion resistance of the reinforcement were reduced by chlorides. Further, the chloride threshold in SAFP solution was 10 times larger than simulated cement pore solution, due to the competitive adsorption between OH−/silicates and chlorides. [ABSTRACT FROM AUTHOR]

The development of a green alternative that can partially or completely substitute the Ordinary Portland cement (OPC) as a practical construction material with low CO 2 footprint is an important subject to researchers for decades. The use of artificial pozzolanic materials, e.g. fly ash, slag, silica fume, etc. cannot meet the huge-scale demand for cement replacement. Kaolinitic clay, with its high pozzolanic reactivity after activation and abundant resources worldwide, is regarded as a promising supplementary cementitious material (SCM) for cement. Recent studies have addressed that the utilization of calcined kaolinitic clay as SCM can effectively improve the properties of cement products. This paper presents a comprehensive review of the research progress on activated kaolinitic clay as SCM in the last decade. It systematically introduces the essential properties, activation mechanism and pozzolanic reactivity assessment of kaolinitic clay. Application of calcined clay in two different cementitious systems (calcined clay blended cement and limestone calcined clay cement) is reviewed from the aspects of workability, mechanical properties, and long-term durability properties with the mechanism discussion. Finally, the environmental and economic impacts of the application of calcined clay in different cementitious systems are discussed. [ABSTRACT FROM AUTHOR]