A direct comparison is made between the effectiveness of Al, Mg, their alloy (Al3Mg4), and Si powders as additional fuels in explosives using the thermobaric effect. The experiment produced calorimetric measurements of the detonation heat and a record of the overpressure histories which were used to determine the quasistatic pressure (QSP) in an explosion chamber after the detonation of charges from mixtures containing 30 % fuel and 70 % RDX passivated with wax. The measured heat values indicate that Al-Mg alloy is a more effective additional fuel during anaerobic post-detonation reactions than Al and Mg separately. Silicon also exothermically reacts with the detonation products, but the released heat only compensates for the lower amount of RDX in the charge. Similar to the calorimetric measurements, the lowest value ofQSPwas obtained for the mixture with Si powder. In contrast to anaerobic conditions, silicon proved to be an equally effective thermobaric additive as Al, Mg, and Al-Mg powders in air explosions.