Avoiding cracking and curling in concrete flooring upon which water-based adhesives are employed
View Patent ↗The invention provides a method for making a concrete floor slab using sub-grade waterproofing in a manner that favors the use of water-based adhesives for affixing floor covering materials. The method comprises casting a hydratable cementitious composition onto a flooring membrane, the composition having a shrinkage reduction admixture and a water:cementitious binder ratio sufficiently low that substantially all of the water moisture is retained in the hydration reaction, and achieving a fully adhered bond with the flooring membrane.
1. Method for making a concrete floor structure, comprising:
applying onto a substrate having a horizontal upward-facing surface a continuous waterproofing membrane having a polymeric film carrier sheet having two major sides and a self-adhering, pressure-sensitive waterproofing adhesive layer disposed on at least one of said two major sides, said waterproofing adhesive comprising a synthetic adhesive having an average thickness of 2–60 mils; said adhesive being selected from butyl rubber based adhesives, polyisobutylene based adhesives, polyisobutyl based adhesives, acrylic based adhesives, vinyl ether based adhesives, styrene-isoprene-styrene based adhesives, styrene-ethylene-butylene-styrene based adhesives, and styrene-butadiene-styrene based adhesives; and said waterproofing adhesive layer side being disposed in an upwards direction when said membrane is applied onto said substrate; said waterproofing membrane further comprising a protective layer comprising an elastomeric coating layer, or a finely divided particulate layer, or both of said layers whereby said protective layer is operative to resist foot traffic while permitting concrete to be cast onto said adhesive and protective layers so as to bond mechanically with said adhesive layer; and
casting a hydratable mortar or concrete composition, which comprises a hydratable cementitious binder and water in a water/cementitious binder ratio of no less than 0.20 and no greater than 0.45 by weight, onto said waterproofing adhesive layer and protective coating layer side of said waterproofing membrane and allowing said composition to bond to and form a horizontal slab upon said membrane, said composition further comprising a comb polymer polycarboxylate superplasticizer in an amount no less than 0.03 and in an amount no greater than 5.0% based on dry weight of hydratable cementitious binder in said composition, said comb polymer polycarboxylate superplasticizer having a carbon-containing backbone with pendent cement-anchoring members and pendent oxyalkylene groups; and said mortar or concrete composition further comprising at least one shrinkage reducing admixture in an amount no less than 0.05% and in an amount no greater than 5.0% based on dry weight of said hydratable cementitious binder, said at least one shrinkage reducing admixture being selected from the group consisting of an oxyalkylene glycol, an oxyalkylene ether adduct of an alcohol, glycol, or glycerol, and an ammonium salt of tall oil fatty acid; and said mortar or concrete composition further having a vapor transmission rate equal to or less than 3 pounds/1000 square feet/24 hours at 3–90 days after placement.
2. The method of claim 1 wherein said shrinkage reducing admixture comprises di-propylene glycol tertiary butyl ether and di-propylene glycol.
3. The method of claim 1 wherein said mortar or concrete composition further comprises fibers.
4. The method of claim 1 wherein said shrinkage reducing admixture comprises a mixture of a first component (a) including at least one alkyl ether oxyalkylene adduct represented by the formula RO(AO)nH wherein A is an alkylene group, O is an oxygen atom, R is an alkyl group, and n is an integer from 1 to 3; and a second component (b) including an oxyalkylene glycol represented by the formula HO(AO) m H wherein A is an alkylene radical, O is an oxygen atom, and m is an integer of 1 to 3.
5. The method of claim 1 wherein said first component (a) further comprises dipropylene glycol t-butyl ether, tripropylene glycol t-butyl ether, or mixtures thereof; and said second component (b) further comprises dipropylene glycol, tripropylene glycol, or mixtures thereof.
6. The method of claim 1 wherein said protective coating is acrylic.
7. The method of claim 1 further comprising applying a water-based adhesive layer onto said composition within 3–90 days after casting said mortar or concrete composition onto said membrane; and applying a floor covering onto said water-based adhesive layer within 3–90 days after casting said composition onto said membrane.