BONDING OLD AND NEW CONCRETE.
The difficulty so long found in bonding together new and old concrete has been obviated by a recent patent. This bond consists of an extract of coal tar, used instead of water as the mixing agent for neat Portland cement. The mixture is laid in 1/8-in. to 1/4-in layers on the old concrete surface, and immediately followed by new concrete or mortar. The inventor says that the compound is entirely insoluble and forms a complete and monolithic bond between the old and new work.