The first section of this two-part article dealt with the use of mechanical and thermic methods in the demolition of concrete. This, the second and final section, discusses the use of explosives, radar waves and outlines operating procedures. The use of explosives for demolition requires an expert knowledge of both the nature of the charge being used and its action. A misfire, or partial explosion of a series of charges, can prove both expensive and dangerous to rectify. The most important advance in explosive engineering has been the development of millisecond delay electric blasting caps. These have made possible major demolitions within city limits without causing damage to neighboring structures, buried services, or even the most delicate equipment. Even with a large explosion, vibration can be kept down to the level of that caused by a passing truck. The technique uses large numbers of strategically located charges that are kept very small. The shot is wired in series which enables each charge to be fired in a prescribed pattern. Accurate location of the charges at critical stress points utilizes the structure's own weight to complete the destruction. Such a method depends on a very careful analysis of the structural forces prevailing, and requires fault-free placement of the charges. For these reason problems of this nature should be referred to an explosives specialist. The English have done some experimenting with the use of a beam of high power microwaves to produce intense local heating sufficient to crack and split away concrete. The theory is based on driving a wedge of heat into the mass of concrete. These radar waves are applied to the concrete through a rectangular copper tube or probe designed to channel and concentrate at one point the power generated by the microwaves. British scientists are now confident that only minor technological difficulties remain before the tool can be made available to the construction industry, since the theory and operating practicality of the device has been proven. Whatever the method chosen, or the size of the job, procedure to be followed must revolve around several key factors: services, such as gas and water; access; loadings; structural members; and worker protection to assure an adequate job can be done.