You are here:

Construction Industry/Rock salt finish on driveway, grey concrete

Advertisement

Expert: - 7/9/2008


Question
Roger, I'm experiencing a rust color stain in the small salt created pockets of the rolled finish and some small dribbles of rust runs on concrete on in-between areas of a driveway and sidewalk. I used a limestone rock and do not think ASR is the issue.  Can an alkali (like rock salt) hang around(year ago when poured) and expose a surface steel and react and cause this stain or is it salt in a limestone reacting with a sparse amount of iron?  I'm miffed as this is new to me in the ten years in the business.  Thoughts?

Answer
Brian

It could be the water used in the cement mixture.  Water with a high iron content.  My experience with stains is usually caused by the limestone leaching white marks. Yes, the salt left in little pockets may not have been fully washed away.  As the minute amount of water in the little pockets evaporated, the salt remained.  This along with the irons in the agregate may be the culpret.

Also, what is the agregate used in the ready-mix?  It may contain high iron content also.  Concrete companies are constantly looking for the best buy if they don't mine their own agregate.  Perhaps the pits they previously mined are played out and the new one has a high iron content.

Hope this has been helpful.

Roger

Construction Industry

All Answers

Answers by Expert:

Ask Experts

Volunteer

Roger Zona

Expertise

I am experienced in all types of construction: residential, industrial and commercial; single family, multi-family, mid-rise and high rise buildings (16 story office building) as well as remodeling, additions and tenant improvements. I can field most any question that relates to general construction. I have consulted with infrastructure (utility) contractors also and have a good general knowledge of underground utility construction for subdivisions and commercial projects.

Experience

After college, I began my career in the construction industry. I chose to become an apprentice Architect and 4 yrs later I opened my own architectural design firm. Six years later I moved to Florida to buy & develop land and build. I became a State of Florida Certified General Contractor and operated my business for 45 years. I built all types of residential and commercial buildings including warehouses, shopping centers, high rise apartments and office buildings and developed sites for other contractors. I retired and became a consultant to the construction industry. I maintain my license and continuing education requirements, operate a small construction company and write a weekly newspaper column for the Palm Beach Post (a Cox publication) with the byline "Ask The Contractor". I am the "technical editor" for a publisher of books that relate to home maintenance.

Organizations
Previously - NAHA Currently - FLCA (Florida Licensed Contractors Assoc.)

Publications
Palm Beach Post newspaper - weekly Q & A column Happy Herald monthly real estate publication - monthly column

Education/Credentials
Michigan State University University of Detroit BS in Engineering

Past/Present Clients
I built a home in Palm Beach for a member of the Pulitzer Family. I was responsible for the completion of a twin hi-rise condominium project for G.E. Credit. I was a partner in the successful development of a P.U.D. (Planned Urban Development) subdivision. I represented the largest home builder from France (Bati Service, S.A.) in the development of a subdivision and the design and construction of the homes.

©2012 About.com, a part of The New York Times Company. All rights reserved.