FIELD

This relates to construction materials, and in particular, to structural assembly boards.

BACKGROUND

Magnesium oxide (MgO) cements are used in the construction industry as building material. Cement may be produced by the reaction between magnesium oxide, magnesium sulfate, and water to produce a cementious material.

Cements can be used as a construction material, for example in construction boards, to provide a structural insulated panel that is flame retardant, mould resistant, and recyclable.

SUMMARY

In an embodiment, a structural assembly board may be made from a composition of high-purity MgO, the composition providing properties to reduce manufacturing time, reduce curing time, and maximize structural properties of the board such as strength.

According to an aspect of the invention, a composition for use in making a structural assembly board is provided.

In an embodiment, the composition comprises magnesium oxide (MgO); magnesium sulfate; water; reinforcing fibers; and adhesive.

In another embodiment, the reinforcing fibers are at least one of basalt, polypropylene, hemp, and/or flax. The reinforcing fibers may 1-2 wt % of the composition.

In another embodiment, the adhesive is 2-4 wt % of the composition.

In another embodiment, the composition is free of fly ash.

In another embodiment, the composition comprises aggregate. The aggregate may be at least one of fly ash and perlite.

In another embodiment, the composition further comprising polycarboxylates and polyol polymers.

In another embodiment, the composition further comprises an organic acid. The organic acid may be at least one of citric acid, tartaric acid, sodium malate, adipic acid, tartaric acid and potassium tartarate.

According to another aspect, a structural assembly board made from the composition of the present invention is provided.

In an embodiment, the structural assembly board is free of mesh, e.g. structural reinforcing fiberglass mesh. In another embodiment, the structural assembly board comprises structural reinforcing mesh.

In another embodiment, the structural assembly board has a pore diameter of less than 2 mm.

In another embodiment, the structural assembly board has a density of less than or equal to 1.2 g/mL.

According to another aspect of the invention, a method of manufacturing a structural assembly board is provided.

In another embodiment, the method comprises: dissolving magnesium sulfate in water to form a brine solution; dissolving magnesium oxide in the brine solution to form a cement mixture; mixing the cement mixture with reinforcing fibers; and curing the cement mixture in a mould. The water may be about 40° C. before magnesium sulfate is dissolved into the water. The molar ratio of MgSO4:H2O may be about 1:18-23.

In another embodiment, the cement mixture is cured with at least one conditions selected from 50-90% humidity, 20-35° C., an atmosphere enriched in CO2, and curing for at least 13 days.

In another embodiment, the method further comprises adding organic acid to the solution to promote formation of phase-5 crystalline structure in the cement mixture, the organic acid being 0.1 wt % to 2.5 wt % of the cement mixture. The organic acid may be at least one of citric acid, tartaric acid, sodium malate, adipic acid, and potassium tartarate.

In another embodiment, the method further comprises adding aggregate and reinforcing fibers to the solution.

In another embodiment, the method further comprises cooling the solution to a temperature less than or equal to 35° C. before dissolving magnesium oxide in the solution. The solution may also be about 25° C. to 45° C. when the magnesium oxide is dissolved in the solution.

In another embodiment, the method further comprises mixing the cement mixture for less than 1.5 hours.

In another embodiment, the magnesium oxide has at least two different particles sizes. The magnesium oxide may have a first particle size having a surface area of about 30 m2/g and a second particle size of about 70 m2/g.

In another embodiment, the method further comprises adding at least one of carboxylic functionalized amphiphilic molecules, phosphonic functionalized amphiphilic molecules, and/or polymers to the brine solution.

In another embodiment, the method further comprises adding at least one of NaH2PO4, KH2PO4, and H3PO4, sodium silicate to the solution to improve water resistance.

In another embodiment, the method further comprises coating the board in a hydrophobic film.

