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Watergels Vs Emulsions

In order to evaluate bulk explosives, it is worth going through the main characteristics of the different types present in the market. Bulk explosives today are dominated by three different families of explosives, namely ANFO, emulsions and watergels. In general terms, the following characteristics apply to these families:

Watergels

  • High energy content ( RIOFLEX ~ 911 cal/g);
  • Low water content (~10%). Better use of explosive energy as less water (inert) has to be heated to the explosion temperature (~2500 K);
  • Uses high energy water soluble fuels;
  • 100% Water resistant. RIOFLEX is crosslinked in the borehole which renders it resistant to dynamic ground water in boreholes and stemming contamination;
  • Totally pumpable. Makes possible a consistent displacement of the borehole water interface by loading from the bottom up;
  • Constant density. No need for in-hole chemically gassing. This facilitates accurate charge and stemming lengths;
  • Uniform performance irrespective of water presence in the boreholes;
  • Universal bulk explosive for wet/dry conditions. Makes it possible to drill expanded patterns consistently, irrespective of weather conditions.

UEE’s RIOFLEX belongs to this family

Emulsions

  • Medium energy content (700-800 cal/g), less than standard ANFO;
  • High water content: 18 ~ 20%;
  • Low cost fuels (diesel, etc);
  • 100% water resistant;
  • Chemically gassing is required to render the emulsion detonable. Other forms of lowering density are too expensive.
  • Low cost, weak explosive. Straight emulsion is never used alone for the previous reason. Strong bulk emulsions would be prohibitively expensive;
  • Emulsions cannot be crosslinked economically. Lower viscosity than watergels which renders them susceptible to dynamic water disruption and stemming penetration;
  • The obvious low cost way of enhancing emulsion performance is by dry additions of ANFO and/or Ammonium Nitrate prills to lower the overall water content within similar density ranges;
  • Emulsions are normally marketed not as a single universal product but rather as a series of Heavy ANFO’s intended for either dry or wet holes:

+ Dry Holes :

  • Normally mixture of 30% emulsion and 70% ANFO. The emulsion fills the voids between AN prills with a noticeable increase in density;
  • Basically an "enhanced ANFO";
  • Very low water resistance;
  • Not pumpable. Only augerable from the collar of the hole and therefore requires a completely dry hole in order to be effective;
  • Can be used in bigger patterns than standard ANFO because of the increased density.

+ Wet Holes

  • Mixture of 70% Emulsion and 30% ANFO;
  • Basically an "enhanced emulsion";
  • Water resistant;
  • Pumpable;
  • Effective in wet holes as long as the pattern stays similar or slightly bigger than an ANFO pattern in the same rock.

Emulsions came into the market as a low cost bulk explosive for the big volumes of the mining industry. Both emulsions and heavy ANFOs find their best application in mining where big hole diameters and quantities justify a sacrifice in performance for a lower unit cost. In mining, fragmentation and heave is not the main goal of blasting as most of the rock blasted will go to the mine dump handled by huge loading and hauling equipment. The only rock that has to be fragmented is the ore, which is a small percentage of the total rock blasted.

In contrast to this, with quarry applications most of the rock has to be crushed and sold as a low cost product for the construction and civil works industry. Crushing of quarry materials only proceeds down to sizes of millimetres. Primary crushing in quarries is greatly affected by the degree of rock fragmentation in the quarry face. Whereas, in mining primary crushing is only a marginal cost compared with secondary and tertiary crushing to the size of microns which is beyond the range of explosive fragmentation. These different realities make emulsions and heavy ANFO’s the best choice for mining applications. In fact, the main reason for the explosives companies to switch their explosive technology to emulsions and Heavy ANFO’s is the need to compete in the big explosives mining markets.