the molten silver braze material being sucked by capillary action into the bore between the carbide tip insert and the walls of the bore to thus securely retain each of the carbide tips firmly brazed in positon in the head 4 as illustrated in fig1 application of the tool to a surface 19 of a concrete block 21 and the rapid reciprocation of the tool in such a way that the carbide tips 13 impinge against the top surface 19 of the concrete effects a destruction of that surface or a 34 scarifying 34 of the surface by rupturing the top surface to expose the underlying aggregate it has been found that when the carbide tips 13 are secured in the head 4 in an inclined attitude and pattern as illustrated in fig1 through 3 each of the carbide tips 13 presents an arcuate edge portion designated in fig3 by the numeral 22 which impinges against the surface 19 of the concrete to effect rupturing thereof it has also been found that the edge 22 of each of the carbide tips that impinges against the concrete surface i e the first point of impact is the highest point on each of the carbide tips with the arcuate edge of the carbide tip on opposite sides of the highest point progressively biting into the surface of the concrete to effect its destruction in the embodiment of the invention illustrated in fig3 it will be seen that the carbide tips 13 are all inclined in the same direction i e the axes of the cylindrical.