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Lynn Javoroski CSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski

Post Number: 871
Registered: 07-2002
Posted on Friday, May 08, 2009 - 12:16 pm:   Edit PostDelete PostPrint Post

Does anyone have a paragraph or two specifying a medium sandblast finish? I've been asked to write such a thing for the structural engineer to include in his concrete spec. I know the architect will need samples, and a mock-up, and that it's considered "medium", and PCI says that means about half the surface is exposed aggregate. Is there anything else I can include?
Richard Gonser AIA CSI CCCA
Intermediate Member
Username: rich_gonser

Post Number: 4
Registered: 11-2008
Posted on Friday, May 08, 2009 - 12:57 pm:   Edit PostDelete PostPrint Post

This is what I've used on a lot of tilt-up buildings in Southern California.
1.4 SUBMITTALS
D. Field Sample: Prepare concrete wall sample to indicate range of sandblast finish textures for preliminary selection by Architect. Upon approval, produce final 50 square foot sample on concrete wall for final approval by Architect. [This is used where we really want to get involved with the Owner in the execution of this in the field.]
3.10. ABRASIVE-BLAST FINISH
A. Abrasive-Blast Finish: Provide abrasive-blast finish where indicated on the Drawings. Abrasive-blast finish is noted as "sandblast" or "sandblasted" on the Drawings.
1. Perform abrasive blasting 24 to 72 hours after casting when concrete strength ranges between 1000 and 1500 psi (6.9 and 10.3 MPa).
2. Coordinate with formwork construction, concrete placement schedule, and formwork removal to ensure that surfaces to be abrasive blasted are treated at the same age for uniform results.
B. Surface Continuity: Perform abrasive-blast finishing in as continuous an operation as possible, utilizing same work crew to maintain continuity of finish on each surface or area of Work. Maintain required patterns or variances in depths of blast to match design reference sample or mockup.
C. Depth of Cut: Use an abrasive grit of proper type and gradation to expose aggregate and surrounding matrix surfaces to match design reference sample or mockup, as follows:
1. Brush: Remove cement matrix to eliminate surface sheen and expose face of fine aggregate. No reveal.
2. Light: Expose fine aggregate with occasional exposure of coarse aggregate and uniform color. Maximum reveal 1/16-inch (1.5 mm).
3. Medium: Generally expose coarse aggregate with slight reveal. Maximum reveal 1/4-inch (6 mm).
4. Heavy: Expose and reveal coarse aggregate to a maximum projection of one-third of its diameter; reveal 1/4- to 1/2-inch (6 to 12 mm).
D. Abrasive Blasting: Abrasive blast corners and edges of patterns carefully, using back-up boards, to maintain uniform corner or edge line. Determine type of nozzle, nozzle pressure, and blasting techniques required to match design reference sample or mockup.
E. Concrete Cleaning: After abrasive blasting to required depth is completed, clean surface with commercial concrete cleaner, as produced by ProSoCo or equal, according to the manufacturer's instructions and recommendations.
1. Thoroughly neutralize and flush cleaning solution from finished surfaces with water under pressure.
2. Protect adjacent materials and finishes from washing and run-off.
Richard Gonser AIA CSI CCCA
Advanced Member
Username: rich_gonser

Post Number: 5
Registered: 11-2008
Posted on Friday, May 08, 2009 - 12:59 pm:   Edit PostDelete PostPrint Post

FYI, the 24 to 72 hours and PSI issues in A.1 are minimums.
Lynn Javoroski CSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski

Post Number: 872
Registered: 07-2002
Posted on Friday, May 08, 2009 - 01:12 pm:   Edit PostDelete PostPrint Post

Thank you! That's great.
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre

Post Number: 875
Registered: 07-2002


Posted on Monday, May 11, 2009 - 02:38 pm:   Edit PostDelete PostPrint Post

however, be sure and ask for a sample. one firm's "medium" is another firm's "light" and every designer will have a different visual image of what they want. the visual look is very dependent on the operator. Ask for 3 sample panels or so -- say, 4' x 4' size, in some portion of the building where it won't matter what they look like.
Lynn Javoroski CSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski

Post Number: 873
Registered: 07-2002
Posted on Monday, May 11, 2009 - 03:24 pm:   Edit PostDelete PostPrint Post

Thanks. We've requested initial samples 12x12, and 50 sq. ft. mock-ups on an area that will be back-filled. We've stated that the mock-up has to be repeated until the architect is satisfied. And they can't change equipment or the guy doing it once it's approved. We wound up not including the definition of "medium" at this point (it's a 90% estimate package), but can put it in if we need it. From what we have, they should be able to put a dollar amount to the finish.

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