Abstract
Coal bottom ash is normally used as aggregate in mortars and concretes. When it is ground, its characteristics are modified. Therefore, the assessment of its long-term durability must be realized in depth. In this sense, an accelerated chloride ingress test has been performed on reinforced mortars made of Portland cement with different amounts of coal bottom ash (CBA) and/or coal fly ash (CFA). Corrosion potential and corrosion rate were continuously monitored. Cement replacement with bottom and fly ash had beneficial long-term effects regarding chloride penetration resistance. Concerning corrosion performance, by far the most dominant influencing parameter was the ash content. Chloride diffusion coefficient in natural test conditions decreased from 23 × 10−12 m2/s in cements without coal ashes to 4.5 × 10−12 m2/s in cements with 35% by weight of coal ashes. Moreover, the time to steel corrosion initiation went from 102 h to about 500 h, respectively. Therefore, this work presents experimental evidence that confirms the positive effect of both types of coal ashes (CBA and CFA) with regard to the concrete steel corrosion.
Highlights
Chloride penetration from seawater into concrete in coastal areas and the associated risk for reinforcement corrosion is recognized as the most important deterioration mechanism for offshore and coastal reinforced concrete structures worldwide [1,2]
The influence of coal fly ash on chloride ingress and resulting reinforcement corrosion in concrete has been reported in many studies over the last decades [18,19,20]
A standardized setup based on chloride ingress by applying an electrical field was used to study the initiation stage of chloride induced reinforcement corrosion in several mortar mixes made of coal bottom ash, coal fly ash and common Portland cement
Summary
Chloride penetration from seawater into concrete in coastal areas and the associated risk for reinforcement corrosion is recognized as the most important deterioration mechanism for offshore and coastal reinforced concrete structures worldwide [1,2]. Coal fly ash is frequently used in mortars and concretes exposed to chloride environments because the pozzolanic additions have a significant influence on the chloride ion transportation. The influence of coal fly ash on chloride ingress and resulting reinforcement corrosion in concrete has been reported in many studies over the last decades [18,19,20]. The influence of coal fly ash in cement-based materials on the corrosion processes is mainly due to microstructural changes, lime consumption due to the pozzolanic reaction and binding capacity. A standardized setup based on chloride ingress by applying an electrical field was used to study the initiation stage of chloride induced reinforcement corrosion in several mortar mixes made of coal bottom ash, coal fly ash and common Portland cement. Corrosion assessment of coal bottom ash in combination with coal fly ash in reinforced mortars was investigated
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