Manufacture of wood-cement composites from Acacia mangium: Mechanistic study of compounds improving the compatibility of Acacia mangium heartwood with Portland cement

Numerous inorganic compounds were screened to identify those capable of minimizing the inhibitory effect of Acacia mangium heartwood on the setting of cement. It was hypothesized that the most effective compounds would be ones that could accelerate the hydration of cement and form complexes with inhibitory phenolic extractives found in the heartwood of A. mangium. Our hypothesis proved correct since compounds such as SnCl₄, AlCl₃, and FeCl₃ and/or their ionic species that were able to bond with the phenolic heartwood constituents of A. mangium as well as accelerate cement hydration were generally more effective at strengthening cement hydration in the presence of A. mangium heartwood than compounds that simply accelerated cement hydration. Compounds containing Ni²⁺, Ag⁺, Fe³⁺, and Co²⁺, that bonded to phenolic constituents of A. mangium heartwood, but lacked the ability to strongly accelerate cement hydration increased maximum hydration temperature attained in wood-cement mixes. The findings suggest that complexation of phenolic heartwood extractives may be an important mechanism by which inorganic compounds reduce the inhibitory effect of certain wood species on the hydration of cement. A combination of compounds including a cost-effective accelerator (such as CaCl₂ or MgCl₂) and an efficient chelating agent (containing such ions as Al³⁺, Sn⁴⁺ or Fe³⁺) may have considerable synergistic effects and could potentially enable wood cement composites to be manufactured from A. mangium.