Abstract: Apparatus and method for experimentally determining the compressive material strength of tubular products includes a housing having a cylindrical cavity therein, top and bottom end caps closing opposite ends of the cavity, tubular bladder means mounted in the cavity and defining a pressure chamber larger than the tubular products to be tested and a fluid receiving space between the bladder means and the wall of the cavity, a plurality of small balls substantially filling the pressure chamber around the tubular product being tested, means for pumping hydraulic fluid into the fluid receiving space to cause the bladder means to apply pressure uniformly to said small balls and thence uniformly over the external curved surface of the tubular product. Means are included to continuously monitor and display the magnitude of the pressure applied to the tubular specimen, and to detect and signal tube failure. Tubular specimens can be instrumented to monitor additional testing characteristics.

Abstract: A concrete column forming tube is provided for receiving poured concrete therein to produce a concrete column and which is characterized by producing surface characteristics on the concrete column including a matte finish without seam lines of the forming tube. A flexible cylindrical liner is positioned in a generally friction-fit relationship within an elongate rigid cylindrical tube constructed of partially-overlapped spirally-wound plies of paper adhered together and defining an inside wall surface having spiral seam lines thereon. The flexible liner is constructed of a paperboard layer secured at butted edges and having an inside wall surface of desired paper fiber matte texture and a thickness sufficient to bridge and cover the spiral seam lines on the inside wall surface of the rigid tube to prevent the formation of seam lines on the outside surface of the produced concrete column.