The use of renewable and bio-based composites is of great importance in the construction industry as they promote the sustainability due to their environment-friendly nature. Hemp-based concretes have been of great interest and prominent bio-composites in the recent years owing to their superior hygroscopic and thermal properties, however, they have inadequate mechanical strength. This research investigates a new type of bio-composite based on the mixture of magnesium phosphate cement (MPC), fly ash (FA) and corn stalk (CS). The study determines the feasibility of using this composite as an insulation and structural material. Several concrete mixtures were formulated with different concentrations (varying from 5% to 30% CS content) and two sizes of corn stalk (LCS and SCS) to develop corn stalk magnesium phosphate cement concrete (CS-MPC concrete). The compressive strength, thermal conductivity, capillary water uptake and water absorption properties of all the bio-composites were investigated. The study concluded that CS-MPC concrete falls in the category of lightweight concrete, and exhibited the improved thermal (lambda = 0.0510 and 0.0986 W.m(-1).K-1 with 30% CS content for LCS-MPC and SCS-MPC concrete) and mechanical properties (fc' =6.98 MPa and 9.44 MPa with 20% CS content for LCS-MPC and SCS-MPC concrete; fc' = 1.75 MPa and 2.60 MPa with 30% CS content for LCS-MPC and SCS-MPC concrete) which are imperative for non-structural and structural applications. Moreover, CS-MPC composites also showed better hygroscopic performance (capillary water uptake) in comparison to previous studies. Morphology of CS-MPC composite by SEM revealed that CS and binder had good interaction with each other during the hydration process. Finally, it was concluded that CS as plant aggregate and MPC as binder with advanced thermal and mechanical properties are better alternatives as compared to hemp hurd and cement or lime for production of bio-composite. Further tests to determine the important properties of this bio-composite are also under consideration. (C) 2018 Elsevier B.V. All rights reserved.