Concrete Made with Calcium-Enriched Fly Ash


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Title: Concrete Made with Calcium-Enriched Fly Ash

Author(s): Shui Cuijuan, Gong Luoshu, and Wang Haimin

Publication: Special Publication

Volume: 91


Appears on pages(s): 387-412

Keywords: calcium; carbonation; compressive strength; concrete durability; concretes; fly ash; freeze-thaw durability; x-ray diffraction.

Date: 2/1/1986

Fly ash in China contains low CaO (5%) and is obtained by burning bituminous coal. Thus such a fly ash concrete exhibits low early strength at an optimal dosage of 10-20%. Two methods were adopted to increase the dosage of fly ash (1) introducing calcium directly during burning or (2) as an additive. The effect of dosage of such fly ash on strength, shrinkage, frost resistance, carbonation and steel corrosion of concrete was investigated. Method 1 is effective in improving the activity of fly ash and permits the optimal dosage of fly ash to increase by 30-4O%. Early strength of concrete is also increased. Method 2 is applicable to steam-cured fly ash concrete at a high dosage (5O-60%). X-ray diffraction analysis was used to study the process of reaction between fly ash and cement.