Title:
Rebound in Dry-Mix Shotcrete: Influence of Type of Mineral Admixture
Author(s):
V. Bindiganavile and N. Banthia
Publication:
Materials Journal
Volume:
97
Issue:
2
Appears on pages(s):
115-119
Keywords:
carbon black; fly ash; shotcrete; silica fume.
DOI:
10.14359/813
Date:
3/1/2000
Abstract:
The high rebound in dry-mix shotcrete has severe implications both on its long-term durability and the mechanical performance in service. The use of mineral admixtures is often recommended as a way of reducing rebound, but the exact influence of the admixture dosage rate, shape, and mean size of their particles on the rebound is not clearly understood. In the research reported herein, four mineral admixtures—silica fume, fly ash, high reactivity metakaolin, and carbon black—were investigated in plain and fiber-reinforced dry-mix shotcrete for rebound and other properties. These admixtures represent particle sizes ranging from 0.05 to 10 mm and particle shapes ranging from spherical to plate-like. Results indicate that while fly ash is not as effective, both silica fume and carbon black substantially reduce the rebound. The performance of high reactivity metakaolin lies somewhere in between. Overall, it appears that the mean particle size of the admixture influences the rebound far more than the shape of its particles.