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A contractor we supply is going to pour a number of exposed architectural walls with 8000 psi, 50% slag mix. In samples, the concrete has a very dark green color, like it is stained. The color is not fading very fast. Will the color completely disappear? Does chemical curing compound have any...
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Is there a good way to correlate core compressive strength and flexural strength? I have a job in which there was only one beam broken, at 28 days, and there are not enough sets to perform any statistical analysis. We are planning to core the pavement and are looking for a comparison between the...
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I am working on providing material for crane counterweights. What is considered a normal weight loss (in pounds per cubic foot) for concrete from its plastic weight to a normal exposure weight after a month or two? My guess would be in the area of a pound or two per cubic foot.
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About 3 hours after our contractors poured a concrete patio, it began to rain and continued to rain for 2 hours. How will that compromise the integrity of the concrete with respect to strength, durability, and so on over the long term?
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Seven days after our contractor poured a concrete driveway, the concerned homeowner called us, instead of the contractor, when he started noticing small pop marks throughout the concrete. After speaking with the concrete finisher and after considering all of the possibilities, we concluded it was...
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What are the effects of using fly ash in concrete pavements? Does it have an impact on abrasion resistance of the mix? Are case studies or field data available, especially where more than 30% fly ash was used in the mix?
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Editor's note: Two readers responded to recent articles on self-consolidating concrete (SCC).
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Editor's note: Two readers responded to recent articles on self-consolidating concrete
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I have a customer who tore out a slab with delamination problems. He subsequently found some sections where the #4 bar had not bonded to the concrete at all. Naturally, he is assuming the concrete is "bad." Besides oil and rust what other reasons can explain the lack of...
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Is it common to get different air readings when using a pressure meter and a roll-a-meter or volumetric meter? I continually get a difference of about 0.8% to 1%, but I feel very sure my meters are calibrated correctly. The higher reading is from the pressure meter.
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Does the water for concrete have to be completely void of salt (from seawater)? What happens if it is not?
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We are trying to use regular transit mixers to produce roller compacted concrete (RRC). Most of our markets do not have a central mixer available. We have developed a mix that discharges fairly well from a non-paving mixer. It has sand (39%), #67 limestone (10%), #8 pea gravel (48%), and Type C fly...
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The drivers at one of our plants have been using about 800 to 850 gallons of fresh water to wash out their mixers at the end of their shift. The amount of wash water often becomes a problem when we’re busy in the summer. Is there any way to reduce this quantity? I've heard that some producers are...
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My husband is a concrete contractor. He does basements, walls, slabs, etc. A doctor has told him that he has "concrete palsy." The first time it appeared was after he had cleaned out the inside of a drum on a truck, which involved vibration and a lot of dust. About three days afterward the skin on...
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A flooring contractor has experienced problems on four occasions over the years with his two-part polyurethane floor covering not bonding to our concrete slab-on-grade. He has said that the acid-etch process prior to installing the covering did not react very well with our slab surface, based on...