Abstract: A method of cementing a wellbore comprising preparing a wellbore cementing composition comprising a cementitious materials and a modified biopolymer additive wherein the modified biopolymer additive is the reaction product of a process comprising contacting a biopolymer and an organic carbonate to form a reaction mixture and subjecting the reaction mixture to a temperature of from about 100° F. to about 250° F. and placing the wellbore cementing fluid in the wellbore. A method of cementing a wellbore comprising contacting a modified biopolymer additive with a cementitious slurry to produce a wellbore cementing composition having an initial viscosity, v0; placing the wellbore cementing composition to a desired depth in a subterranean formation wherein the wellbore cementing composition has a transitional viscosity, vt, during placement in the subterranean formation and a final viscosity, vf, at the desired depth wherein vf?vt>v0; and allowing the wellbore cementing composition to set.