S-420 features the high quality and high strength concrete test capping material. It is designated as the most reliable product by many professional testing labs. The high reputation of S-420 raised the demand. Modern buildings such as high-rise construction request S-420 as the minimum strength as qualification. The water to gypsum ratio for S-420 is recommended to be 21-22%. After simply mixing with water, the gypsum is ready to use immediately and will be fully solidified after approximately 30 minutes and reach the strength over 420 kgf/cm2, Equals to 6000psi.