Rapid setting, water durable binder composition

A method of providing a lightweight cement board comprising:

• forming a mixture of:
• a) a reactive powder comprising
• cement at about 10-40 wt. % of the reactive powder,
• β-stucco at about 30-75 wt. % of the reactive powder, and
• pozzolanic material at about 5-30 wt. % of the reactive powder, wherein the pozzolanic material comprises fly ash,
• b) a plasticizer in an amount equal to about 0.05-3 wt. %, preferably 0.1-3 wt. %, of the reactive powder, and
• c) water, wherein the reactive powder:water weight ratio is 100:40-70
• d) 5-50 vol. %, on a wet basis, entrained air;
• and
• e) optional additive selected from at least one member of the group consisting of aluminum sulfate, nucleating agent, retarder, alkanolamine, air-entraining agent, metal phosphate, inorganic secondary set accelerator, lightweight filler, secondary filler, and scrim;
• under conditions which provide an initial slurry temperature of at least about 40° F.

A cement board having a density of about 40 to 80 pcf and having a continuous phase resulting from the curing of an aqueous mixture comprising:

• a) a reactive powder comprising
• cement at about 10-40 wt. % of the reactive powder,
• β-stucco at about 30-75 wt. % of the reactive powder, and
• pozzolanic material at about 5-30 wt. % of the reactive powder, wherein the pozzolanic material comprises fly ash,
• b) a plasticizer in an amount equal to about 0.05-3 wt. % of the reactive powder, and
• c) water, wherein the reactive powder:water weight ratio is 100:40-70
• d) 5-50 vol. %, on a wet basis, entrained air;
• and
• e) optional additive selected from at least one member of the group consisting of aluminum sulfate, nucleating agent, retarder, alkanolamine, air-entraining agent, metal phosphate, inorganic secondary set accelerator, lightweight filler, secondary filler, and scrim.