Concrete coloring compositions and methods

A method, comprising the steps of:

• a) applying to the surface of a fiber cement substrate composition comprising a reaction mixture of (i) a first acid which has a pKa less than 6;
• (ii) a weak base, wherein the conjugate acid of the weak base has a pKa less than 7 and greater than the pKa of the first acid;
• and (iii) one or more metal salts that impart a color when the composition is applied to and reacts with the fiber cement substrate;
• b) causing the composition to react with the substrate and develop color;
• and
• c) applying a protective coating to cover the fibercement surface.

A method, comprising the steps of:

• (a) incorporating a salt of a protonated base into an aqueous liquid carrier, said protonated base having a pKa of less than about 7;
• (b) incorporating a salt of a transition metal into the aqueous liquid carrier;
• and
• (c) causing the aqueous liquid carrier to contact and react with a cementitious surface so as to color the cementitious surface;
• and
• (d) drying the cementitious surface.

A system, comprising:

• (a) a cementitious surface;
• and
• (b) an aqueous composition in contact with the surface so that the composition can react with the surface and develop color, the composition derived from ingredients comprising (i) aqueous species comprising a weak base in equilibrium with a conjugate acid of the weak base, said conjugate acid of the weak base having a pKa of less than about 7;
• and (ii) aqueous species comprising a transition metal ion and a corresponding anion, wherein the salt corresponding to the transition metal ion and the anion is a Lewis acid.