API SPEC 10A pdf download Cements and Materials for Well Cementing 4 Requirements 4.1 Specification, Chemical, and Physical Requirements 4.1.1 Classes and Grades 4.1.1.1 General Well cements shall be specified using the classes A, B, C, D, G, or H and the grades ordinary (O), moderate sulfate-resistant (MSR), and high sulfate-resistant (HSR). Composite well cements shall be specified using classes...