When referring to portland cement, “soundness” refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion (PCA, 1988[1]). This destructive expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO). Most portland cement specifications limit magnesia content and expansion. The typical expansion test places a small sample of cement paste into an autoclave (a high pressure steam vessel). The autoclave is slowly brought to 2.03 MPa (295 psi) then kept at that pressure for 3 hours. The change in specimen length due to its time in the autoclave is measured and reported as a percentage. ASTM C 150, Standard Specification for Portland Cement specifies a maximum autoclave expansion of 0.80 percent for all portland cement types.
Standard Test Methods
- AASHTO T 107 and ASTM C 151: Autoclave Expansion of Portland Cement
- Portland Cement Association (PCA). (1988). Design and Control of Concrete Mixtures. Portland Cement Association. Skokie, IL.↵