An admixture includes a cementitious component, an unprocessed biomass component, calcium chloride, calcium carbonate, and an adhesive element. The admixture is suitable for mixing with water to form a flowable material that cures to produce a hardened material. A flowable material includes the admixture and water. A method of producing a flowable material includes turning on a mixer and adding an unprocessed biomass component to a drum of the mixer. The unprocessed biomass component is sprayed with an adhesive element to form a first composition. Calcium carbonate is added to the first composition in the mixing chamber, to form a second composition. The second composition is mixed. A cementitious component is added to the mixed second composition in the mixing chamber, to form a third composition, which is mixed with water and calcium chloride to produce the flowable material. The flowable material cures to form the hardened material.