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Perform releasing of prestressed steel in pretensioned piles in such an
order that eccentricity of prestress will be minimized. Gradually release
tension in strands from anchorage. Detension after approval by pile
manufacturer's quality control representative. Perform transfer of
prestressing force when concrete has reached a minimum compressive strength
of [_____] MPa psi.
2.3.6
Marking
Mark pile to identify in-place impact face.
Marking shall be clearly
visible during driving.
2.4
PRODUCT QUALITY CONTROL
Where piling is manufactured in a plant with an established quality control
program as attested to by a current certification in the PCI Certification
Program for Quality Control, perform product quality control procedures in
accordance with PCI MNL-116. Where piling is manufactured by specialists
or in plants not currently enrolled in the PCI Certification Program for
Quality Control, set up a product quality control system in accordance with
PCI MNL-116 and perform concrete and aggregate quality control testing
using an independent commercial testing laboratory approved by the
Contracting Officer in accordance with the following.
2.4.1
Aggregate Tests
Take samples of fine and coarse aggregate at the concrete batch plant and
test. Perform mechanical analysis (one test for each aggregate size) in
accordance with ASTM C 136 including determination of the specific gravity.
Tabulate the results of the tests in accordance with ASTM C 33.
2.4.2
Strength Tests
Sample concrete in accordance with ASTM C 172 at the time the concrete is
deposited for each production line. Compression tests shall conform to
methods of ASTM C 39 and ASTM C 31/C 31M. Perform slump tests in
accordance with ASTM C 143/C 143M. Mold at least six cylinders per day or
for every 15 cubic meter 20 cubic yards of concrete placed, whichever is
greater. Test two cylinders of the set at 7 days of 14 days, or at a time
for establishing transfer of prestressing force (release strength) and
removal of pile from forms. Perform strength tests 28 days after molding
using the remaining cylinders of the set. Cure the cylinders in the same
manner as the piles and place at the point where the poorest curing
conditions are offered. This is the coolest point in the bed for steam
curing. Cylinders to be tested at 28 days shall be moist cured.
2.4.3
Changes in Proportions
If, after evaluation of strength test results, the compressive strength is
less than the specified compressive strength, make adjustments in the
proportions and water content and changes in the temperature, moisture, and
curing procedures as necessary to secure the specified strength. Submit
changes to the Contracting Officer in writing.
2.4.4
Compressive Strength Test Results
Evaluate compression test results at 28 days in accordance with ACI 214R
SECTION 02395
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