CRCA s Industry Affairs & Steep & Shingle Committees May 17, 2016

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1 CSI Chicago Tech Roundtable Structural Lightweight Concrete & Roof Assemblies CRCA s Industry Affairs & Steep & Shingle Committees May 17, 2016

2 CRCA s Contact Info Bill McHugh, CSI, CSC Chicago Roofing Contractors Assn. bill@crca.org

3 10,000+ Circulation Roofing Contractors Roofing Consultants Specifiers GC s Bldg Owners FREE SUBSCRIPTION info@crca.org CRCA TODAY FREE

4 Structural Lightweight Concrete & Outline Define Issues Discussion Roofing Issues 4

5 Concrete Definitions NWC Normal Weight Concrete Sand Lightweight Siliceous Aggregate LWSC Lightweight Structural Concrete Carbonate Aggregate Lightweight Aggregate Lightweight Insulating Concrete Cellular Perlite Vermiculite 5

6 Normal Weight Concrete Siliceous aggregate. Concrete made with normal-weight aggregates consisting mainly of silica or compounds other than calcium or magnesium carbonate, which contains more than 40-percent quartz, chert or flint. Sand-lightweight. Concrete made with a combination of expanded clay, shale, slag, slate, sintered fly ash, or any natural lightweight aggregate meeting ASTM C 330 and possessing equivalent fire-resistance properties and natural sand. Its unit weight is generally between 105 and 120 pcf (1680 and 1920 kg/m3). 6

7 Define Normal Weight Concrete Normal Weight Concrete 150 lb/ft 3 Regular Aggregates - Rock Lightweight Structural Concrete About 110 lb/ ft 3 Expanded shales, clays Air pockets mean water is held longer 7

8 Structural Lightweight Concrete IBC 2015 Carbonate aggregate. Concrete made with aggregates consisting mainly of calcium or magnesium carbonate, such as limestone or dolomite, and containing 40 percent or less quartz, chert or flint. Lightweight aggregate. Concrete made with aggregates of expanded clay, shale, slag or slate or sintered fly ash or any natural lightweight aggregate meeting ASTM C 330 and possessing equivalent fire-resistance properties and weighing 85 to 115 pcf (1360 to 1840 kg/m3). 8

9 Structural Lightweight Concrete No cautions from Concrete Industry Roofing Industry Moisture Accumulation Adhesion Loss Adhesive Issues with H2O & other adhesives Metal Fastener Corrosion Insulation R-value loss Microbial Growth 9

10 Structural Lightweight Concrete Advantages Less Weight/Floor Less Shrinkage Less Cracking Fire Resistance per inch > NWC Structural Strength LEED Credit Disadvantages Pockets hold Water ½ gallon extra water/sf Slow drying times Rewetting occurs No Standards for deck acceptability (Same for NWC) 10

11 M Dupuis Photo

12 M Dupuis Photo

13 M Dupuis Photo

14 Lightweight Insulating Concrete Cellular. A lightweight insulating concrete made by mixing a preformed foam with Portland cement slurry and having a dry unit weight of approximately 30 pcf (480 kg/ m3). Perlite. A lightweight insulating concrete having a dry unit weight of approximately 30 pcf (480 kg/m3) made with perlite concrete aggregate. Perlite aggregate is produced from a volcanic rock which, when heated, expands to form a glass-like material of cellular structure. 14

15 Lightweight Insulating Concrete Vermiculite. A light weight insulating concrete made with vermiculite concrete aggregate which is laminated micaceous material produced by expanding the ore at high temperatures. When added to a Portland cement slurry the resulting concrete has a dry unit weight of approximately 30 pcf (480 kg/m3). 15

16 Lightweight Insulating Concrete Vented Edge Details Vapor Retarders Nailed Base Sheets 16

17 Structural Lightweight Concrete Issues (NRCA Paper) Adhesion Waterproofing Roofing Insulations Moisture Accumulation Metal and Fastener Corrosion Insulation R-Value Loss Microbial Growth 17

18 Structural Lightweight Concrete Issues Manufacturers Exclusions Warranties Deck suitable for accepting Roof Covering Good Roofing Practice Wind Uplift after aging on SLWC? Can t tell what is SLWC or NWC in Roofing.. Deck Accepted 18

19 Issues Structural Lightweight Concrete ASTM F2170 Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes. Pass or Fail?? 65-85% RH in <90 days % RH in 6 months. Is a Roofing Contractor a Concrete Specialist? 19

20 Structural Lightweight Concrete NRCA s Position - General Decision of when a newly placed concrete substrate is ready to be covered with a new roof system be made by the building s structural engineer, general contractor, concrete supplier, concrete placement contractor, each of whom likely will have more knowledge than the roofing contractor about the particular concrete s curing and moisture release rates. It also may be useful to consult the building s project or roof system designer and roof system manufacturer. 20

21 Structural Lightweight Concrete NRCA s Position NRCA s Premise and Position is consistent with the flooring industry Furthermore in new construction, NRCA recommends designers not specify and construction managers and general contractors not use lightweight structural concrete for roof decks or as toppings for roof decks. In NRCA s opinion, the risks of moisture related problems associated with lightweight structural concrete roof decks outweigh the potential benefits. 21

22 Structural Lightweight Concrete NRCA s Position In the event lightweight structural concrete is used. Specify Drying Parameters with ASTM F2170 Maximium 75% RH, lower depending on insulation. DO NOT USE perliite, woodfiber, paper facers 22

23 Structural Lightweight Concrete NRCA s Position Reroofing Above Deck Venting Design Perimeter Venting Seal Concrete Moisture In High Bond Strength Vapor Retarder High Quality 12-15mil thick two part epoxy, (Flooring) 23

24 CRCA s Contact Info Jason Wilen, AIA, ALA, CDT, RRO National Roofing Contractors Assn. jwilen@nrca.net Bill McHugh, CSI, CSC Chicago Roofing Contractors Assn. bill@crca.org

25 CSI Chicago Tech Roundtable Structural Lightweight Concrete & Roof Assemblies CRCA s Industry Affairs & Steep & Shingle Committees May 17, 2016