State of the art in the technology of using blast furnace slag gravel for concrete members

More than twenty years has already passed since the establishment of JIS for blast furnace slag gravel. However, the annual quantity of use accounts for only 1.5 million tons because of the very few examples of big construction projects. On the other hand, the needs for recycling and saving construction materials have been highlighted recently because of the serious shortages of new natural resources. This report introduces two examples of experimental uses of blast furnace slag gravel in current technological developments. One use is as an aggregate for underground concrete tank-pit in the construction of an LNG facility. The technical method explained keeps the pumpability of fresh concrete mixed with blast furnace slag gravel. It also focuses on the evaluation of the strength of slag grave in extremely low temperatures. The other example deals with the effective use of blast furnace slag gravel as a fine aggregate by mixing it with natural sand. The study explains the measures for an adequate delay in the hardening of a fine slag aggregate after air-cooling. Moreover, an effective method is proposed in mixture of a fine slag aggregate and natural sand.