ASTM C956-04 (R2019) PDF Download

ASTM C956-04 (R2019) is a standard specification that outlines the minimum requirements for the installation of cast-in-place reinforced gypsum concrete over permanent formboard. The standard covers various aspects of the installation process, including the design of subpurlins to support live and dead loads, the use of steel shapes that meet the requirements of the specification, the testing of mineral fiber formboard, and the fabrication of hexagonal reinforcing mesh, rectangular reinforcing fabric, gypsum concrete, and expansion filler strip.

The standard specifies that subpurlins should be placed transversely to the purlins and primary framing, with spacing determined by the size of the formboards. Cross tees should be provided at formboard ends that are supported by purlins or primary framing. Formboards should be positioned face down on the flanges of the supporting members, with the ends on top of the purlins. The mesh of wire fabric should be located with the main longitudinal wires at right angles to the subpurlins and adjacent to the formboard at midspan between the purlins.

Furthermore, the standard outlines the placement of expansion filler strips against walls, curbs, nailers, or other rigid surfaces that the gypsum concrete will abut. It also provides guidelines for the mixing and placement of gypsum concrete, emphasizing the importance of thorough mixing without overmixing. It is important to note that the standard includes references to explanatory material in the form of notes and footnotes, which are not considered requirements of the standard.