Method and apparatus for casting a concrete product with a substantially horizontal slipform casting process, wherein the concrete mix is fed at least in one step through a limited cross-section moving progressively along with the cast, whereby the height of the product forming part is changed during the cast. The bendable structure, which is preferably configured as a grid, includes a spring that imparts increasingly bowed contours to the grid upon increasingly arched deflection of the spring relative to the seat frame and the guide rail. A plurality of wheels are mounted so as to permit movement of the cart in a direction generally along the longitudinal axis.