Chapter 7 Cast-In-Place Concrete
prestressing tendons. Inspections shall include tendon size and strength, chair height, tendon profile, tendon snaking elimination, horizontal ties between chairs and condition of sheathing.
d. Stressing of tendons. The SIER shall verify that tendon stressing operations are in compliance with project specifications. Stressing of tendons shall not start before the specified minimum strength of field- cured test cylinders has been achieved and verified by the SIER and approved by the SER. Continuous monitoring of stressing of tendons is required. Elongation records shall be made and checked against project specifications. Tendon failures or tendon elongations not in compliance with project specifications shall be rejected and the SER shall make recommendations in writing for remedial actions.
e. Concrete. The SIER shall verify use of proper concrete design mix, monitor placement of concrete, and perform inspections and testing listed in NCSBC-Table 1704.4. Continuous monitoring shall be required at the point of discharge from trucks / batch plant, and at the point of deposit / consolidation of concrete. Verify that water added at the site does not exceed that allowed by the mix design.
f. Weldability of reinforcement. If steel reinforcement other than ASTM A 706 is to be welded, the SIER shall verify that the weldability of the reinforcement has been determined in accordance with NCSBC -1903.5.2.
g. Welding of reinforcement. Special inspection of welding of reinforcement is required in accordance with both NCSBC -Table 1704.4 Item 2 and NCSBC -Table 1704.3 Item 5B. Continuous monitoring of welding of reinforcing steel shall be provided where required by NCSBC -Table 1704.3 Item 5B.
Concrete shall be tested in accordance with NCSBC-1905.6 and this section.
NCSBC-1905.6 Evaluation and acceptance of concrete. The criteria for evaluation and acceptance of concrete shall be as specified in Sections 1905.6.2 through 1905.6.5.5.
NCSBC-1905.6.1 Qualified technicians. Concrete shall be tested in accordance with the requirements in Sections 1905.6.2 through 1905.6.5. Qualified field testing technicians shall perform tests on fresh concrete at the job site, prepare specimens required for curing under field conditions, prepare specimens required for testing in the laboratory, and record the temperature of the fresh concrete when preparing specimens for strength tests. Qualified laboratory technicians shall perform all required laboratory tests.
NCSBC-1905.6.2 Frequency of testing. The frequency of conducting strength tests of concrete shall be as specified in Sections 1905.6.2.1 through 1905.6.2.4.
NCSBC-1905.6.2.1 Minimum frequency. Samples for strength tests of each class of concrete placed each day shall be taken not less than once a day, nor less than once for each 150 cubic yards (115 m3) of concrete, nor less than once for each 5,000 square feet (465 m2) of surface area for slabs or walls.
NCSBC-1905.6.2.2 Minimum number. On a given project, if the total volume of concrete is such that the frequency of testing required by Section 1905.6.2.1 would provide less than five strength tests for a given class of concrete, tests shall be made from at least five randomly selected batches or from each batch if fewer than five batches are used.
NCSBC-1905.6.2.3 Small volume. When the total volume of a given class of concrete is less than 50 cubic yards (38 m3), strength tests are not required when evidence of satisfactory strength is