Oh yes, the voice of experience right here. evil grin David Ferrin www.jaws-users.com ----- Original Message ----- From: "Boyce, Ray" <[EMAIL PROTECTED]> To: <blindhandyman@yahoogroups.com> Sent: Wednesday, February 06, 2008 6:51 PM Subject: [BlindHandyMan] Concrete, Snow and Ice
> Summary: Concrete driveways are susceptible to damage from deicing salts > and freezing temperatures. Ice crystals form in the cement and need a > place to > expand. Your concrete should have an additive mixed in to create air > pockets for these ice crystals. > > DEAR TIM: Winter is fast approaching. Within the past month, I had a new > concrete driveway and sidewalk installed. I am concerned about surface > scaling > caused by deicing salts and freezing temperatures. Is my new concrete at > risk and what, if anything, can be done to minimize the damage caused by > salt > and ice? A. L. > > DEAR A. L.: Many homeowners ask this same question. Because of the > relatively high initial expense of installing concrete, homeowners want > their driveways > and sidewalks to last as long as possible. Virtually everyone knows that > deicing salts and freezing temperatures can damage concrete - concrete > that has > not been ordered, placed, finished and cured properly that is. > > Your new driveway is extremely susceptible to damage in its first year. > Only use sand for traction. Concrete, contrary to popular belief, is not > a totally > 'solid' object. It contains microscopic passageways. These passageways > are created during the initial crystallization process as concrete > transforms from > the liquid to the solid state. These tunnels are created as the needles > of the interlocking > cement > paste crystals grow. > > Water cannot be compressed. When water freezes and turns into ice, its > volume expands by about nine percent. If there is not sufficient room > within the > passageways to accommodate this expansion, the ice can begin to break > the needles of the interlocking cement paste crystals. Your freshly > poured concrete > already has a high water content. Although it appears dry, there is > quite possibly a large quantity of free water still within the crystal > structure. > > Deicing salts can also cause similar problems. The presence of salts in > concrete can create high internal pressures. Deicing salts melt snow and > ice and > create a salty brine which is absorbed into concrete. As the temperature > drops and ice crystals begin to form, the concentration of the unfrozen > salt brine > begins to increase. This brine actually attracts water creating a > pressure difference within the network of cement paste crystals. This > pressure can and > does fracture some of the crystals. > > Fortunately, there are things that can be done to minimize the damage > from these forces. When concrete is mixed, additives can be included > which create > very small air bubbles within the concrete as it dries. These air > bubbles provide a place for the expanding ice crystals to relieve their > pressure. Residential > concrete should have an air content of five to seven percent. > > Concrete strength is a function of the amount of cement powder that is > added to the mix. This strength is often measured in pounds per square > inch or PSI. > Residential concrete subjected to freezing or deicing salts should > attain a minimum strength of 4,000 PSI. You can order concrete with > higher PSI strengths. > The concrete can only attain this strength if it is properly cured. A > liquid curing compound should be applied to your concrete as soon as the > final finish > has been applied. > > When finishing or placing concrete, never add extra water to the mix. > Also, do not sprinkle water on top of the concrete as it is being > finished. Never > finish concrete that has standing water on the surface. > > These practices dilute the amount of cement paste at the surface of the > concrete. With less cement, there are fewer crystals to hold things > together. > > You can also apply > special sealants > to the concrete which minimize the absorption of water or salt brine. > Many of these sealants are highly effective and can often help to > protect concrete > which has been improperly installed. These sealants should have the > capability to breathe. Water vapor from the soil beneath the slabs must > be able to > evaporate into the air. > > ********************************************************************** > This message and its attachments may contain legally > privileged or confidential information. If you are not the > intended recipient, you must not disclose or use the > information contained in it. If you have received this e-mail > in error, please notify the sender immediately by return > e-mail and delete the e-mail. > > Any content of this message and its attachments which > does not relate to the official business of Eraring Energy > must be taken not to have been sent or endorsed by > Eraring Energy. No warranty is made that the e-mail or > attachment(s) are free from computer virus or other defect. > ********************************************************************** > > > > [Non-text portions of this message have been removed] > > > > To listen to the show archives go to link > http://acbradio.org/handyman.html > or > ftp://ftp.acbradio.org/acbradio-archives/handyman/ > > The Pod Cast address for the Blind Handy Man Show is. > http://www.acbradio.org/news/xml/podcast.php?pgm=saturday > > Visit The Blind Handy Man Files Page To Review Contributions From Various > List Members At The Following address: > http://www.jaws-users.com/JAWS/handyman/ > > Visit the archives page at the following address > http://www.mail-archive.com/blindhandyman@yahoogroups.com/ > > If you would like to join the JAWS Users List, then visit the following > address for more information: > http://www.jaws-users.com/ > For a complete list of email commands pertaining to the Blind Handy Man > list just send a blank message to: > [EMAIL PROTECTED] > Yahoo! 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