Houstons source for info on custom decorative concrete, drivewayS, patios, Stamped/patterned concrete, admixtures for concrete. Also offer links to other related resources

Monday, December 13, 2004

Affordable Concrete Contractors Houston TX, Concrete Patios, Driveways, Foundations

ENTER SITE

Recently, I was contacted by KTRC radio Station in regards to the nationwide
rising concrete costs.

"Apparently we're having a nationwide material shortage" Said David Hunt,
Director of the Stamped Concrete Institute. "All the sand, Gravel and Portland
Cement is being brought in from all over the country to quench Houston's thirst
for Concrete".

The top exporters of cement to the United States are Canada, Thailand and,
ironically, China, according to the Portland Cement Association, a trade
association based in Skokie, Ill. But because of its growing domestic demand,
China has sharply curtailed its cement exports, the association said.

Concrete is vital in Houston Texas because home builders and ten of the
nations Largest Concrete Contractors in the U.S. are voracious consumers of it,
using it for Streets, Overpasses, foundation slabs, driveways and sidewalks.
And Houston is particularly vulnerable to shortages because it imports about 40
percent of its cement compared with a nationwide average of 20 percent.


Many Concrete Plants are trying to lower their costs by "cutting" the concrete
with up to 20% fly ash, versus 100 % Pure Portland Cement.

Fly ash is a fine, glass-like powder recovered from gases created by coal-fired
electric power generation. U.S. power plants produce millions of tons of fly ash
annually, which is usually dumped in landfills. Fly ash is an inexpensive
replacement for portland cement used in concrete, while it actually improves
strength, segregation, and ease of pumping of the concrete. Fly ash is also
used as an ingredient in brick, block, paving, and structural fills.

There is an abundance of Radioactive Elements in Coal and Fly Ash says the
U.S. Geological Survey (USGS)

"Assessment of the radiation exposure from coal burning is critically dependent
on the concentration of radioactive elements in coal and in the fly ash that
remains after combustion."

Data for uranium and thorium content in coal is available from the U.S.
Geological Survey (USGS), which maintains the largest database of
infor-mation on the chemical composition of U.S. coal

For this reason, We at ConcreteForever.com buy our Concrete From Metro
Concrete in Houston because they do not use this radiocactive substance that
is being currently tested for long term effects.

A draft summary of the courthouse project released Oct. 12 by city officials
estimated rising concrete and steel prices added $10 million to $15 million to
the cost of the CourtHouse project. But no numbers have been released to
support those estimates, nor is there a breakdown of how much was originally
budgeted for concrete, steel and other construction materials.

To build the courthouse today, steel and concrete would cost $10.1 million, or
4.5 percent of the $232 million budget. But that $10.1 million does not come
close to explaining the additional $36 million that Mayor John Peyton told City
Council members last November would be needed to complete the courthouse
complex.

City officials now say concrete and steel were not the only construction
materials to rise in price.

"It's misspeaking to say it's just steel and concrete [driving costs up]. It's other
construction materials as well," said Rick Mullaney, general counsel for the city.

In the last year, costs for cement have increased 7.8 percent; asphalt, 6.2
percent; ductile iron pipe, 15.4 percent; corrugated steel pipe, 11.5 percent;
reinforced concrete pipe, 5.8 percent; PVC water pipe, 16.8 percent; lumber,
42.3 percent; reinforcing bar, 42.9 percent; aluminum sheet 6.7 percent and
stainless steel sheet, 19.4 percent, according to an Oct. 25 news release by
the Engineering News Record.

But the city has not provided any estimates of extra costs of materials needed
for the courthouse project, other than steel and concrete.

To build the new Duval County Courthouse, 5,700 tons of structural steel and
3,024 tons of reinforcing steel are needed. In addition to that, 47,000 cubic
yards of concrete are needed, said Brian Murray, vice president of Skanska
USA Building Inc. and project director for the courthouse complex.

Steel costs about $648 a ton, said Tom Cusick, a former administrator at
Bethlehem Steel Co. That equates to $3.7 million for the courthouse.
Reinforcing steel costs about $900 a ton, or $2.7 million, Murray said. And
concrete, according to the Oct. 25 release by the Engineering News Record,
costs, on average, $76.94 per cubic yard, or $3.6 million.


Because concrete must be both strong and workable, a careful balance of the
cement, aggregates, entraining admixtures, hardeners, sand & water ratio is
required when making concrete. Our unique formula is as follows: Tricalcium
silicate 50 % Ca3SiO5 or 3CaO.SiO2
Dicalcium silicate 25 % Ca2SiO4 or 2CaO.SiO2
Tricalcium aluminate 10 % Ca3Al2O6 or 3CaO .Al2O3
Tetracalcium aluminoferrite 10 % Ca4Al2Fe10 or 4CaO.Al2O3.Fe2O3
Gypsum 5 % CaSO4.2H2O. The equation for the hydration of tricalcium silicate is
given by:
Tricalcium silicate + Water--->Calcium silicate hydrate+Calcium hydroxide + heat
2 Ca3SiO5 + 7 H2O ---> 3 CaO.2SiO2.4H2O + 3 Ca(OH)2 + 173.6kJ

Upon the addition of water, tricalcium silicate rapidly reacts to release calcium ions,
hydroxide ions, and a large amount of heat. The pH quickly rises to over 12 because
of the release of alkaline hydroxide (OH-) ions. This initial hydrolysis slows down
quickly after it starts resulting in a decrease in heat evolved.

The reaction slowly continues producing calcium and hydroxide ions until the
system becomes saturated. Once this occurs, the calcium hydroxide starts to
crystallize. Simultaneously, calcium silicate hydrate begins to form. Ions precipitate
out of solution accelerating the reaction of tricalcium silicate to calcium and
hydroxide ions. The evolution of heat is then dramatically increased.

The formation of the calcium hydroxide and calcium silicate hydrate crystals provide
"seeds" upon which more calcium silicate hydrate can form. The calcium silicate
hydrate crystals grow thicker making it more difficult for water molecules to reach the
unhydrated tricalcium silicate. The speed of the reaction is now controlled by the rate
at which water molecules diffuse through the calcium silicate hydrate coating. This
coating thickens over time causing the production of calcium silicate hydrate to
become slower and slower.

When water is added to cement, each of the compounds undergoes hydration and
contributes to the final ConcreteForever.com product. Only the calcium silicates
contribute to strength. Tricalcium silicate is responsible for most of the early strength
(first 7 days). Dicalcium silicate, which reacts more slowly, contributes only to the
strength at later times.

Steel Reinforcement: Preformed bars #3 or greater complying with the requirements
of ASTM A-615, Grade 60, unless otherwise indicated, and of domestic manufacture.
Mesh reinforcement shall conform to the requirements of ASTM A-185.

B. Metal Accessories: Shall include all spacers, chairs, ties, and other devices for
properly spacing, supporting, and fastening reinforcement in place.

C. Cement: Portland cement of North American manufacture conforming to the
requirements of ASTM C-150, Type I or II. Use only one brand of cement throughout
the project, one concrete plant when using integral color.

D. Concrete Aggregates: Shall conform to the requirements of ASTM C-33.
1. Fine Aggregate: Sand shall consist of hard, tough, and preferably siliceous
material, clean, free from mineral or other coatings, soft particles, clay, loam, or
other deleterious matter.

2. Coarse Aggregate: Crushed stone or gravel, having clean, hard, durable,
uncoated particles, free from deleterious matter. The 1-1/2" aggregate shall conform
to gradation #467 and the 3/4" aggregate to the size #67 in Table II of ASTM C-33.
The 3/4" aggregate shall be used for structural slabs, lintel beams, and any other
location where 3/4 of the clear space between reinforcing bars or between bars and
the forms require this size aggregate.

E. Admixtures:

1. Water Reducing Admixture: "Eucon 75" by The Euclid Chemical Company,
Polyheed Non-Chloride by Master Builders, WRDA with Hycol by Grace Construction
Products, or Platocrete 160" by Sika Chemical Corporation. The admixture shall
conform to ASTM C-494, Type A, for proper color pigmentation and not contain more
chloride ions than are present in municipal drinking water.

2. Non-Corrosive, Non-Chloride Accelerator: "Accelguard80" by The Euclid Chemical
Company, or approved equal. The admixture shall conform to ASTM C-494, Type C
or E, and not contain more chloride ions than are present in municipal drinking
water. The admixture manufacturer must have long-term non-corrosive test data
from an independent testing laboratory (or at least a year's duration) using an
acceptable accelerated corrosion test method such as that using electrical potential
measures.

3. Air Entraining Admixture: Conform to ASTM C-260, "Darex AEA" as manufactured
by The Construction Products Division of W.R. Grace & Company, or approved equal
to obtain desired color pigment.

4. Prohibited Admixture: Calcium chloride, thiocyanates or admixture containing
more than 0.05% chloride ions are not permitted.

5. Certification: Written conformance to the above mentioned requirements and the
chloride ion content of the admixture will be required from the admixture
manufacturer prior to mix design review by the Architect.

F. Curing Paper: Water, reinforced appear; "Orange Label Sisalkraft," as
manufactured by the American Sisalkraft
Corporation, "Scuf-Champ,: as manufactured by Ludlow Papers, "Flor-Cur W/S," as
manufactured by Glas-Kraft, or approved equal.

G. Moisture Barrier: "J" Pro Vapor Shield, Super Sampson SS4 or Tu Tuff 4.

H. Color Hardener: L.M. Scofield Company Lithochrome color hardener. Hardener
shall be Brick Red color.

I. Concrete Colorant: L.M. Scofield Company Chromix admixture color shall be
Quarry Red.

J. Release Agent: L.M. Scofield Company Lithochrome antiquing release. Color
shall be broadcast evenly over slab.

K. Floor Slab Sealer: ProSoCo Inc., SLX 100 penetrating sealer.

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