Abstract: A precast roadway slab is pre-tensioned longitudinally and transversely, and may also be post-tensioned. A casting bed has the capability of permitting pre-tensioning of a concrete cast to be carried out within the casting bed in both the longitudinal direction and in the transverse direction. Slots are provided at regular intervals within the side walls and jacking heads of the casting bed for tensioning wires to pass therethrough for pre-tensioning. The process utilizes a multilayer grid of pre-tensioning wires disposed within the casting bed, prior to pouring of the concrete. The cast concrete product can also be made with optional tubular ducts, laid parallel to the longitudinal wires, for post-tensioning subsequent to the cast of the concrete. The post-tensioning of the hardened cast, if called for, takes place at the job site.

Abstract: A precast roadway slab is pre-tensioned longitudinally and transversely, and may also be post-tensioned. A casting bed has the capability of permitting pre-tensioning of a concrete cast to be carried out within the casting bed in both the longitudinal direction and in the transverse direction. Slots are provided at regular intervals within the side walls and jacking heads of the casting bed for tensioning wires to pass therethrough for pre-tensioning. The process utilizes a multilayer grid of pre-tensioning wires disposed within the casting bed, prior to pouring of the concrete. The cast concrete product can also be made with optional tubular ducts, laid parallel to the longitudinal wires, for post-tensioning subsequent to the cast of the concrete. The post-tensioning of the hardened cast, if called for, takes place at the job site.

Abstract: A precast roadway slab is pre-tensioned longitudinally and transversely, and may also be post-tensioned. A casting bed has the capability of permitting pre-tensioning of a concrete cast to be carried out within the casting bed in both the longitudinal direction and in the transverse direction. Slots are provided at regular intervals within the side walls and jacking heads of the casting bed for tensioning wires to pass therethrough for pre-tensioning. The process utilizes a multilayer grid of pre-tensioning wires disposed within the casting bed, prior to pouring of the concrete. The cast concrete product can also be made with optional tubular ducts, laid parallel to the longitudinal wires, for post-tensioning subsequent to the cast of the concrete. The post-tensioning of the hardened cast, if called for, takes place at the job site.

Abstract: A pile cage (2) has a reinforcement structure (4) having a first part (8) adapted to remain in a pile, the first part terminating at a predefined cut-off level (20), and a second part (10) that is protected in order to debond it from concrete cast around it. A split-wailed annular tube (30) is located at the cut-off level (20) and is connected to a supply of pressurised fluid after the concrete has been poured and set. The tube (30) expands under pressure initiating a crack that is propagated by the escape of fluid from the slit (32) towards a centre of the pile at the cut-off level (20). The entire cracked central surface of the cast pile acts as a hydraulic jack separating the pile cap (104) from the remainder of the pile (102).