Cylindrical mould made from a laminated plastic material flat sheet (1 ) and two equal covers, respectively the top cover (2) and the bottom cover (2'), for moulding of composite test pieces for the construction industry, characterized by said flat sheet (1), in its dismantled shape, consists of a substantially rectangular body, defining a narrow strip (5) in its upper end, inferiorly bounded by a marking line (3) throughout its length and which defines the filling maximal limit of said cylindrical mould, said narrow strip presenting cuts (7), which defines respectively tabs (8) and openings (6) and said tabs (8) being foldable in its base, and defining another narrow strip in its lower end (9, 10) provided with a first set of contiguous trapezoidal fringes (9) and a second set of contiguous trapezoidal fringes (10), the said fringes (10) of said second set being equal or smaller than the fringes (9) of the first set, said lower strip ending at a certain distance from the respective side ends of said flat she
