BRIEF INTRODUCTION OF HEAVY ANFO

Heavy ANFO or ammonium nitrate blends are mixtures of ammonium nitrate prills, fuel oil, and slurries. The ratio of the amount of slurry mixed with the ANFO can be changed to offer either a higher energy load or a load which is water resistant. The cost of heavy ANFO rises with increasing amounts of slurry. A disadvantage using the blends is that since the explosive occupies the entire volume of the blasthole any water in the hole is forced upward. This means that one may have to use the blend in the entire hole.

Some operators try to use heavy ANFO in wet holes, however, they don't use mixtures which contain sufficient slurry. To provide the necessary water resistance, it is recommended that at least 50% slurry be used in heavy ANFO which is to be used under wet boreholes conditions.

Figure 1: Heavy ANFO Bulk Loading Truck

Note:
Sensitivity/density of poured heavy ANFO in the blasthole can vary with the addition of microballoons or chemical gassification. In order to fulfill required density, some supplier give recommendation of lag time before stemming.

Figure 2: Example Product of Heavy ANFO

Figure 3: Another Sample Product of Heavy ANFO