Low-carbon magnesium potassium phosphate cement (MKPC) binder comprising caustic calcined magnesia and potassium hydroxide activated biochar from softwood technical lignin

Biochar augmentation in cementitious materials is attractive for enhancing the products' mechanical properties and improving sustainability. Softwood technical lignin biochar (5 wt-%) was used to augment MKPC as a replacement material, with increased surface area through KOH activation. Hard-burned (1000 °C) MgO was used as precursor. XRD and SEM-EDX analyses showed “struvite-K” as the primary component of the MKPC materials. MKPC materials including the 2-hour KOH-activated biochar showed the lowest porosity, highest strength and stiffness. Replacing MKPC with KOH-activated biochar can increase strength properties and reduce MKPC binder usage, providing a sustainable approach for precast applications.