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  • From: Gene GeRue <genegerue AT ruralize.com>
  • To: homestead AT lists.ibiblio.org
  • Subject: Re: [Homestead] Tvo post- concrete May '99
  • Date: Sun, 19 Feb 2006 16:36:35 -0700

This is a wonderful post and I thank Rob for having saved it and now putting it out for us. Very few details I would add. An alternative to rebar today is chopped fiberglass. Just buy it by the bag and mix according to directions. If you order from a concrete plant check the cost and make the decision when you order. Make sure you have more help than you think you will need. I have been put in the position of having to finish a large slab with only an inexperienced and clumsy helper and I damn near killed myself. That total lack or respect cost the friend any further offer of help by me.

ForestHaven wrote:

> Thanks, Tvo. My thinking's much clearer on this project, now.

>>>tvoivozhd---well, I always feel that I have forgotten something
important, and usually have. So here's some parting admonitions:.

a. Drive the job, don't let it drive you. By that I mean plain
concrete sets rapidly. You have a very limited time to place, screed
and finish it. It also must be very well mixed, but not longer than
necessary. The minute you mix water and Portland, the crystalline
structure starts to form. Prolonged mixing destroys its formation and
weakens the end product. Have on hand and employ the proper tools,
equipment and supplies.

b. Work with the weather, not against it. Don't pour concrete when it
will be exposed to rain before setting. Equally important, a 100
degree, sunny day, with a strong wind can turn an easily managed job
into an unmanageable disaster---setting up before it is properly placed,
before voids can be vibrated out, and before it can be screeded flat,
much less floated and finished.
c
. If you must work against the weather, minimize the obvious problems,
i.e., put retarder in the mix if it is hot and windy, accellerator in
the mix if it is cold, or rain threatens.

d. Protect the concrete during the curing process---keep the surface
damp. It helps to cover it so sun and wind don't dry out the surface.
In extremely hot, dry, windy weather, spray it frequently. And protect a
slab against rain with a cover that won't blow away too.

e. Unless you use a plasticizer, you should vibrate any deep sections
to remove voids. Don't overdo it though, prolonged vibration will cause
the concrete mix to separate and stratify---creating a weak point.

f. Similarly, when finishing, you have to float the slab---generally
with a big four-foot bull float on the end of a six-foot handle. You
want to smooth it, but not bring up too much paste to the surface where
it will constantly be powdering off when cured. It takes judgment as to
when to start floating---the concrete should be setting, but not to the
degree you can't work it. A big engine-powered rotary trowel when they
were first introduced, was the best investment I ever made---made
precise timing unnecessary. You could beat down, make a level and
beautiful finish on a slab that was long beyond any control with manual
floating and trowelling.
You may have to walk on the slab when finishing it. Large enough pieces
of wide board or plywood make it possible without impairing the finish.

g. Like painting, preparation makes a hard job easy, or an easy job
impossible. Use a transit if you have one, a water level or carpenter's
level to level your formwork and grade-stakes, if any (pull the latter
when you have screeded to their tops, and work out the voids) Always
have two level formboards across which you can saw your two by four or
two by six screed. In a wide slab, or one in which you are pouring
close to walls, put in a temporary third board so you have two boards
for screedwork. Pull the temporary board out to finish the slab

Use an adequate type and amount of steel---placed and tied properly as
described in most concrete books. You can pull up road mesh with a hook
after pouring concrete, but it is easier to place steel on bridges which
are left in after the pour---it is the only way you can be sure the
steel is adequately encased by concrete, and near lower (and sometimes
upper) surfaces where the tensile strength of steel should be
focussed---in the middle of the slab it will hold it together, but be
otherwise useless, causing unnecessary cracks and lowered resistance to
loads..

h. Where do you want your water to go? On the interior of a house this
applies primarily to kitchen and bath and expected spills, leaks and
overflows. You don't want a leaky pipe draining into the family room,
particularly if the floor cover is susceptible to water damage. So,
while most slabs should be dead level, sometimes you have to create a
grade to a drain. My idea of a simple, easy to care for house is one
you can hose down. In a warm climate and a house with stone, brick or
CEB walls I wouldn't even put in interior drain plumbing for that
purpose, I would slightly slope the slab to a series of perimeter drains
which would of course be screened---and obtain the additional benefit of
bringing outside air at ground level where it is coolest (through grass
shaded by shrubbery)..

i. Improve your understanding beforehand. There are innumerable books
on concrete and masonry. I have quite a few I bought in used bookstores
and library sales for twenty five cents each. For beginners, the books
with a lot of illustrations on all phases and many different
applications of mason's work, are the most helpful. Your local library
will have or can get on interlibrary loan most all the books you will
really need. If you want to buy some, the best places are used
bookstores and library sales, and for new ones, your local
building-supply stores. In the last, among others, you will find the
"Sunset" series, including the "Garden and Patio Building Book"

The "Masonry" book of the Time-Life series appears from time to time in
used bookstores. A couple of very small books you might run across are
"How to Work with Concrete and Masonry" by Darrell Huff,
SBN 06-463354-3, "Concrete and Masonry" by Richard Day (Fawcett
Publications).

Old standbys are "Basic Construction Techniques For Houses And Small
Buildings Simply Explained", prepared by the U.S. Navy (published by
Dover), ISBN0-486-20242-9, and from TAB Books, "Concrete & Masonry",
ISBN 0-8306-5902-1

Your librarian can obtain the two above, and another useful, newer book,
"The Visual Handbook of Building and Remodeling", by Charlie Wing
(Rodale Press), ISBN 0-87857-901-X


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