# Detonability of Ammonium Nitrate Mixtures with the Addition of Organic Materials
## 3 Results and Discussion
### Effect of Amount of Organic Material on Detonation Properties  
The changes in the experimental and calculated detonation velocities (\(D\)) and the calculated detonation heat (\(Q\)) and detonation pressure (\(p_{CJ}\)) with the variation in the volume fraction of rubber and hay are shown in Figure 7.  
As visible from Figure 5, the experimental burst velocity of both the AN/Rubber and AN/Hay mixtures increases with the increase in volume fraction of organic material and reaches its maximum values of 2664 m/s at an 8% volume fraction of hay and 2551 m/s at 15% rubber. For the AN/Rubber mixture, the thermochemical calculation predicts the detonation velocity-volume fraction of the rubber profile similar to that obtained by  
Figure 6: Appearance of steel tube after detonation: (**a**) AN/Rubber (90/10, experiment), and (**b**) ANFO (Autodyn simulation). Figure 7: Changes in calculated detonation velocity, pressure, and heat with variation in volume fraction of rubber (**a**) and hay (**b**). Experimental burst velocities are given for comparison. the experiments; this shows an increase in detonation velocity up to 10.9% by volume (\(D=5002\) m/s), followed by a slow decrease with a further increase in the rubber content. The calculated (ideal) detonation velocity is twice as high as the measured one, which is the consequence of the non-ideal character of detonation under the conditions of this small-cale experiment. Unlike the AN/Rubber mixture, the experimental and calculated detonation velocity-volume fraction profiles are quite different. The calculation predicts a continuous decrease in detonation velocity and pressure with the hay content, while the experiment predicts an increase in velocity with up to 8% of hay. The analysis showed that two factors simultaneously influence the calculated profile: firstly, the composition, and secondly, the density of the mixtures. Compared to rubber, hay contains twice as much carbon and hydrogen per unit of mass. Furthermore, unlike rubber, in addition to carbon and hydrogen, hay contains a certain amount of oxygen. Therefore, its oxygen balance (OB) is more positive than the OB of rubber (OB of hay equals \(-129.4\%\); OB of rubber is \(-332.4\%\)). The result of the above-mentioned calculation is as follows: for the same volume fraction, the AN/Hay mixture produces less H\({}_{2}\)O and CO\({}_{2}\) than the AN/Rubber mixture, which results in a lower detonation heat, velocity, and pressure (Figure 8a). The effect of another factor, density, is shown in Figure 8b. Since hay has a lower density than rubber (\(0.391\) g/cm\({}^{3}\) compared to \(0.466\) g/cm\({}^{3}\)), the addition of hay decreases the density of the AN/Hay mixture more than in the case of the AN/Rubber mixture. Ultimately, the simultaneous action of these two factors, density and composition, results in the calculated detonation velocity-volume fraction profiles of AN/Hay given in Figure 8b. For the sake of validation, we performed the calculation, assuming a constant density of the AN/Hay mixture, and found that detonation velocity continuously increases with the hay content and reaches the maximum value at the zero oxygen balance concentration. This confirms the significant effect of the density of organic material on the detonation velocity. We do not have a sound explanation for why the experimental detonation velocity for the AN/Hay mixture has a very different profile compared to the calculated one. The fact that detonation fails at 15% of hay by volume (6.8% by mass) leads to the conclusion that small-scale experiments are performed at diameters that are close to critical for the AN/Hay mixture, given that a small variation in certain parameters can cause a change in detonation behaviour. For example, the addition of hay may change the failure radius of the mixture or may slow down the decomposition reaction, which will increase or decrease the detonation velocity.