Geopolymer concretes are gaining wide acceptance for alternative material choices in civil engineering and infrastructure applications. The objective of this study is to evaluate structural performance and responses of rectangular plain geopolymer concrete members. Geopolymer concrete specimens with various compressive strengths were experimentally evaluated for torsional strength and deformation. The relations between shear modulus and compressive strength were established. The K factors based on theory of primary torsion were evaluated for design purposes.