CRCA @ CSI Chicago Tech Roundtable Structural Lightweight Concrete & Roof Assemblies

www.crca.org

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

CRCA’s Contact Info •Bill McHugh, CSI, CSC Chicago Roofing Contractors Assn. bill@crca.org – 708-449-3340

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

CRCA @ CSI Chicago Roundtable Structural Lightweight Concrete &

Roofing Issues • Outline

– Define – Issues – Discussion

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CRCA @ CSI Chicago Roundtable Concrete

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

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CRCA @ CSI Chicago Roundtable 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).

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CRCA @ CSI Chicago Roundtable Normal Weight Concrete

• Define – Normal Weight Concrete –

• 150 lb/ft3

• Regular Aggregates - Rock

– Lightweight Structural Concrete

• About 110 lb/ft3

• Expanded shales, clays

• Air pockets mean water is held longer

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CRCA @ CSI Chicago Roundtable 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).

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CRCA @ CSI Chicago Roundtable 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

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CRCA @ CSI Chicago Roundtable Structural Lightweight Concrete

• Advantages – Less Weight/Floor – Less Shrinkage – Less Cracking – Fire Resistance

per inch > NWC – Structural

Strength – LEED Credit

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• Disadvantages • ‘Pockets’ hold

Water ½ gallon extra water/SF

• Slow ‘drying’ times • Rewetting occurs • No Standards for

deck acceptability (Same for NWC)

M Dupuis Photo

M Dupuis Photo

M Dupuis Photo

CRCA @ CSI Chicago Roundtable 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.

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CRCA @ CSI Chicago Roundtable 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).

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CRCA @ CSI Chicago Roundtable Lightweight Insulating Concrete

• Vented Edge Details • Vapor Retarders • Nailed Base Sheets

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CRCA @ CSI Chicago Roundtable Structural Lightweight Concrete

• Issues (NRCA Paper) – Adhesion

• Waterproofing • Roofing • Insulations

– Moisture Accumulation – Metal and Fastener Corrosion – Insulation R-Value Loss – Microbial Growth

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CRCA @ CSI Chicago Roundtable 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…

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CRCA @ CSI Chicago Roundtable Structural Lightweight Concrete

• Issues – ASTM F2170 – Standard Test Method for

Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes’.

• Pass or Fail?? • NWC @ 65-85% RH in <90 days. • SLWC @ 65-85% RH in 6 months.

– Is a Roofing Contractor a Concrete Specialist?

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CRCA @ CSI Chicago Roundtable 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.”

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CRCA @ CSI Chicago Roundtable 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.”

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CRCA @ CSI Chicago Roundtable 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

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CRCA @ CSI Chicago Roundtable 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)

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CRCA’s Contact Info •Jason Wilen, AIA, ALA, CDT, RRO National Roofing Contractors Assn. jwilen@nrca.net – 847-299-9070 •Bill McHugh, CSI, CSC Chicago Roofing Contractors Assn. bill@crca.org – 708-449-3340

CRCA @ CSI Chicago Tech Roundtable Structural Lightweight Concrete & Roof Assemblies

www.crca.org

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