ASTM C926-20b PDF Download

ASTM C926-20b is a standard specification that outlines the requirements for the application of Portland cement-based plaster for both exterior (stucco) and interior work. The standard includes tables for proportioning different plaster mixes and determining the appropriate plaster thickness.

The materials used in the plaster application must meet specific criteria, such as using Portland cement, air-entraining Portland cement, masonry cement, blended hydraulic cement, or plastic cement. Hydrated lime of Type S is also required, along with aggregates like perlite and sand for the base and job-mixed finish coats. Water, admixtures, and fibers are also important components.

The specification provides guidance on preparing solid bases, such as masonry, stone, cast-in-place or precast concrete, through methods like sandblasting, wire brushing, acid etching, chipping, or a combination of techniques. It also addresses important topics such as curing to resist cracking, materials protection and storage, environmental conditions, and the application of plaster, finish-coat, and fog-coat. The plaster application can be done either by hand or machine, up to the specified nominal thickness, on metal and solid plaster bases.