Retarders' effects on some properties of class G cement cured at 80°C

Cement set retarders must assure a predictable time for the cement solidifying at target temperatures to prevent the catastrophic event of cement setting inside a casing and to avoid losses in time and money while waiting on cements with long hardening times. They also must not compromise set cement properties. Calorimetric tests, with sodium lignosulfonate retarder treated at a high pH of 13·4 and temperature of 90°C (SLS-13) revealed a predictable linear change of the class G cement's setting time at temperatures between 50 and 90°C. Comparison of the solid-phase properties of cement hydrated alone or in the presence of several common retarders with those of SLS-13 retarded cement demonstrated that for cements with a similar extent of hydration held at 80°C, SLS-13 improved their compressive strength, decreased the number of voids in the cement body and assured a more compact and less porous morphology. The paper presents comparative thermogravimetric analyses, X-ray diffraction and scanning electron microscopy results of the microproperties of cement hydrated in the presence of sodium gluconate, poly(4-styrenesulfonic acid-co-maleic acid) sodium salt, sodium lignosulfonate or SLS-13 for 17 h at 80°C.