Exposed Aggregate Concrete

Log Out | Topics | Search Moderators | Register | Edit Profile

Thread Last Poster Posts Pages Last Post   Closed: New threads not accepted on this page

Author Message Dean E. McCarty New member Username: Dean_e_mccarty Post Number: 4 Registered: 08-2002 Posted on Tuesday, October 08, 2002 - 12:00 pm:    I am trying to find specification language (products and execution) for exposed aggregate concrete, and I am having great diffuclty. I would appreciate any direction that any of you can offer. If someone has a specification to forward, please send it to my e-mail. dean@mccartyconsulting.com Thanks in advance. Anonymous Posted on Thursday, October 10, 2002 - 03:58 pm:    AIA MasterSpec has Section 02751 for flatwork and 03331 for formed work; both have language for exposed aggregate finishes. Robin E. Snyder Senior Member Username: robin Post Number: 29 Registered: 08-2004 Posted on Monday, October 10, 2005 - 07:23 pm:    Does anyone know of any standards/tolerances etc that apply to exposed aggregate? I have been searching on PCA and ACI's website to no avail. I have a client that has some crummy exp agg and we are looking for some type of industry standards that can be used as a barometer. William Wagner Senior Member Username: bill_black Post Number: 10 Registered: 07-2005 Posted on Tuesday, October 11, 2005 - 08:03 am:    If I remember right ACI's Manual of Concrete Practices has the how-to's of architectural exposed concrete. I have always had to ask a structural engineer for the sections. The problem I have run into is even with this the results are up for interpretation. Dave Metzger Senior Member Username: davemetzger Post Number: 141 Registered: 07-2001 Posted on Tuesday, October 11, 2005 - 09:12 am:    How exposed do you want the aggregate to be? And how uniform the exposure? And even if there were industry standards governing the appearance of exposed aggregate concrete (and I'm not aware of any), the results are still largely dependent on workmanship--the skill and conscientiousness of the mechanic. This is a good example of the value of samples and mockups. Require the submittal of a quantity of 12 inch square samples; use the accepted sample as the basis for a large constructed mockup. Require that the mechanic who will do the final work also do the mockup. The accepted mockup then becomes the standard of workmanship for the project. It's even better if there is a sample made prior to bidding, that is available for bidders to see. Tom Heineman RA, FCSI, SCIP Senior Member Username: tom_heineman Post Number: 60 Registered: 06-2002 Posted on Wednesday, October 12, 2005 - 08:30 am:    The first question is "exposed?" or "seeded?" Exposed is a subtractive process. Sometimes a garden hose and stiff broom will do this. Timing is critical, so you can get into chemical retarders. Now go to the Metzger doctrine of "how exposed?", "how uniform?", "How much do you trust the skill, common sense and conscience of an unknown mechanic?", and "get a couple of 2'x2' job samples". With two samples you can often go the "a little more (or less) this way" route. If the area is large, N mechanics will product N results. That equation is linear. Then there's seeding, an additive process. Very often you will use an identifiable graded stone that is not from your area, and which will be bought from a supplier. The stones can be uniformly small in size and spherical in shape, which often creates a boring and slippery result. As you get into graded mixes with some larger stones, appearance and safety improve, especially if you do not trowel absolutely flat, if you use crushed stone instead of spherical gravel, if you let the color vary, and if you state how much of the matrix you want washed and broomed away before it sets. Don't forget reseeding starved areas before it's too late. I suspect the secret Metzger doctrine is to be there and talk with the mechanic before the samples are made, not just appear afterward to express dissatisfaction. The consummate skill of the specifier comes into play in exposed aggregate work. Can you express in 30 or 40 words what you have in mind? The CA person at the site (hopefully you) will determine the success of the result. Dave Metzger Senior Member Username: davemetzger Post Number: 142 Registered: 07-2001 Posted on Wednesday, October 12, 2005 - 08:53 am:    The "secret Metzger doctrine"? I could tell you what it is, but then I'd have to kill you (inside the beltway humor) John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 427 Registered: 03-2002 Posted on Wednesday, October 12, 2005 - 09:10 am:    I thought that inside the beltway they don't kill anyone, they just launch a five-year long congressional investigation during which you wish you were dead. George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 81 Registered: 11-2004 Posted on Wednesday, October 12, 2005 - 10:05 am:    How about specifying "Acceptable Installers"? We do this by the back door anyway, when we call for installers approved/certified/licensed by the manufacturer. In this case, we don't have a manufacturer, but we probably know which concrete finishers can give us the concrete finish we want. There is a famous ancient masonry spec: "Brickwork like that done by John Doe". Maybe we need to go back to that century old way of specifying what we want, when the skill of the mechanic is the essence of the product quality. Tom Heineman RA, FCSI, SCIP Senior Member Username: tom_heineman Post Number: 62 Registered: 06-2002 Posted on Wednesday, October 12, 2005 - 10:26 am:    One trait I might specify for an "acceptable installer" is "factory trained". It's hard to find an exposed aggregate factory in my area. As a small contractor's office help, I noticed that my boss hired carpenters after asking them to show their hands. (In our small firm, carpenters laid block, cast concrete, and yes, maybe once or twice exposed some aggregate.) I'm not sure what I would look for in a concrete finisher. Alkali burns? Ask Metzger. He probably fixes them with his eyes and looks long and deeply into their souls.