SPC is a sulfur polymer composite material that begins melting between 110 and 120°C (230 and 248°F), with an optimum pour temperature between 130 and 140°C (266 and 284°F). The compressive strength of SPC upon cooling averages 27.6 MPa (4,000 psi). Its mechanical strengths continue to increase for at least two years to approximately triple the original strength. As a proven construction concrete, SPC has demonstrated the ability to survive for years in acids and salts that destroy or severely damage hydraulic concretes in months or even weeks. Perhaps SPC's strongest selling point is that it will always melt and pour at approximately 135°C. This feature will allow hazardous or radioactive waste specimens that do not pass the required tests to be remelted and reformulated until they do pass.