17.1 Inspection
To ensure that the construction complies with the design an inspection procedure should be set up covering materials, records, workmanship and construction.
17.1.1
Tests should be made on reinforcement and the constituent materials of concrete in accordance with the relevant standards. Where applicable, use should be made of suitable quality assurance schemes.
17.1.2
Care should be taken to see that:
- a) design and detail are capable of being executed to a suitable standard, with due allowance for dimensional tolerances;
- b) there are clear instructions on inspection standards;
- c) there are clear instructions on permissible deviations;
- d) elements critical to workmanship, structural performance, durability and appearance are identified; and
- e) there is a system to verify that the quality is satisfactory in individual parts of the structure, especially the critical ones.
17.2
Immediately after stripping the formwork, all concrete shall be carefully inspected and any defective work or small defects either removed or made good before concrete has thoroughly hardened.
17.3 Testing
In case of doubt regarding the grade of concrete used, either due to poor workmanship or based on results of cube strength tests, compressive strength tests of concrete on the basis of 17.4 and/or load test (see 17.6) may be carried out.
17.4 Core Test
17.4.1
The points from which cores are to be taken and the number of cores required shall be at the discretion of the engineer-in-charge and shall be representative of the whole of concrete concerned. In no case, however, shall fewer than three cores be tested.
17.4.2
Cores shall be prepared and tested as described in IS 516.
17.4.3
Concrete in the member represented by a core test shall be considered acceptable if the average equivalent cube strength of the cores is equal to at least 85 percent of the cube strength of the grade of concrete specified for the corresponding age and no individual core has a strength less than 75 percent.
17.5
In case the core test results do not satisfy the requirements of 17.4.3 or where such tests have not been done, load test (17.6) may be resorted to.
17.6 Load Tests for Flexural Member
17.6.1
Load tests should be carried out as soon as
Table 11 Characteristic Compressive Strength Compliance Requirement
(Clauses 16.1 and 16.3)
| Specified Grade | Mean of the Group of 4 Non-Overlapping Consecutive Test Results in N/mm2 | Individual Test Results in N/mm2 |
|---|---|---|
| (1) | (2) | (3) |
| M 15 | ≥ fck + 0.825 x established standard deviation (rounded off to nearest 0.5 N/mm2) or fck + 3 N/mm2, whichever is greater | ≥ fck N/mm2 |
| M 20 or above | ≥ fck + 0.825 x established standard deviation (rounded off to nearest 0.5 N/mm2) or fck + 4 N/mm2, whichever is greater | ≥ fck N/mm2 |
NOTE-In the absence of established value of standard deviation, the values given in Table 8 may be assumed, and attempt should be made to obtain results of 30 samples as early as possible to establish the value of standard deviation.
possible after expiry of 28 days from the time of placing of concrete.
17.6.2
The structure should be subjected to a load equal to full dead load of the structure plus 1.25 times the imposed load for a period of 24 h and then the imposed load shall be removed.
NOTE—Dead load includes self weight of the structural members plus weight of finishes and walls or partitions, if any as considered in the design
17.6.3
The deflection due to imposed load only shall be recorded. If within 24 h of removal of the imposed load, the structure does not recover at least 75 percent of the deflection under superimposed load, the test may be repeated after a lapse of 72 h. If the recovery is less than 80 percent, the structure shall be deemed to be unacceptable.
17.6.3.1
If the maximum deflection in mm, shown during 24 h under load is less than , where is the effective span in m; and , the overall depth of the section in mm, it is not necessary for the recovery to be measured and the recovery provisions of 17.6.3 shall
not apply.
17.7 Members Other Than Flexural Members
Members other than flexural members should be preferably investigated by analysis.
17.8 Non-destructive Tests
Non-destructive tests are used to obtain estimation of the properties of concrete in the structure. The methods adopted include ultrasonic pulse velocity [see IS 13311 (Part 1)] and rebound hammer [IS 13311 (Part 2)], probe penetration, pullout and maturity. Non-destructive tests provide alternatives to core tests for estimating the strength of concrete in a structure, or can supplement the data obtained from a limited number of cores. These methods are based on measuring a concrete property that bears some relationship to strength. The accuracy of these methods, in part, is determined by the degree of correlation between strength and the physical quality measured by the non-destructive tests.
Any of these methods may be adopted, in which case the acceptance criteria shall be agreed upon prior to testing.