a process for producing a composite structural element , which includes the steps of providing a thin - section wall part , placing the thin - section wall part into a mold , applying reinforcing elements to the thin - section wall part , placing a counter - mold onto the mold for forming a mold cavity , and introducing a binder having a foaming agent into said mold cavity via one of injection cannulas and nozzles , after a set time delay a foaming of the binder occurring for encapsulating the reinforcing elements on all sides .