Abstract Expanded shale is a synthetic, porous, lightweight aggregate calcined at high temperature. The properties and characteristics of expanded shale and the concrete made with it were investigated experimentally, and the results have shown that there is a great deal of influence of shale strength and interfacial bond between the shale and cement pastes on the mechanical properties of this concrete. A new technique, called Enveloping Expanded Shale in Cement paste of low water-cement ratio, EESC, is given and some parameters, such as water-cement ratio in the enveloping layer (Wi/Cj) and the thickness proportion of the enveloping layer (Q/C) etc, are defined in this paper. The influence of these parameters on concrete strength was investigated experimentally. Microhardness and pore size distributions of the interface layer were determined, and SEM was used successfully to observe the differences of interfacial bond. The experimental results of mechanical properties confirm that this new technique, EESC, can strengthen expanded shale and improve the interfacial bond. Thus an excellent concrete can be obtained by EESC. Keywords: Expanded shale, Lightweight aggregate, Strength, Interface, Concrete.