Improve your construction quality by referring to IS codes on testing and sampling of concrete
Testing and sampling of concrete is an essential step to ensure the construction meets the quality requirements. But how to figure out which tests to carry out? And what procedure to follow? Enters IS code.
The Indian Standard codes are ready reference guides for construction practitioners covering almost every aspect including tests, procedures, and quality requirements.
Here are four IS codes on methods of testing and sampling of concrete, if referred to, will improve your construction quality.
- IS 1199: 1959
- IS 9013: 1978
- IS 9284: 1979
- IS 3085: 1965
1. IS 1199:1959: Methods of sampling and analysis of concrete
As you know, testing of the raw materials for concrete and concrete, both fresh and hardened, should be part of the quality control program. These tests help achieve higher efficiency of the materials used and greater assurance of the performance of the concrete in regard to both strength and durability. The test should be simple, direct, and convenient to apply. This standard ensures all three.
This code mentions the following procedures:
- Procedure for the sampling of fresh concrete in the field
- Securing and preparing test specimens from hardened concrete
- Tests for workability
- Slump test
- Compacting factor test
- Flow of cement concrete using flow table
- Determination of Consistency of Concrete by Vee-Bee Consistometer Method
- Analysis of freshly mixed concrete
This method of analysis deals with the procedure for determining the proportions of the constituents of freshly mixed concrete, where the nominal size of the largest aggregate does not exceed 38 mm.
- Determination of the specific gravity of aggregates
- Sieve Analysis
- Determination of weight per cubic metre, yield, cement factor, and air content of freshly mixed concrete
- Cement content of hardened Portland cement concrete
- Drying shrinkage and moisture movement tests
The code, however, does not mention tests for the strength of concrete.
For that, you need to refer to IS 516: 1959 - Methods of test for the strength of concrete which covers tests for the determination of the following properties of cement concrete.
- Flexural strength
- Compressive strength
- Modulus of elasticity
One delimiting factor in determining the compressive strength of concrete is that concrete requires 28 days to reach the hardened state.
Suppose you are constructing a dam that expects a strength of 100 kN/m3 but after hardening of concrete, the test results show the strength to be only 50 KN/m3. What now? The work has already progressed and you are lagging behind the schedule. Will you break the structure?
Well, for this situation to not happen, you have I.S. 9013: 1978.
2. IS 9013:1978- Method of Making, Curing and Determining Compressive Strength of Accelerated Cured Concrete Test Specimens
This standard describes the method of making, curing, and testing in compression concrete specimens cured by two accelerated methods.
These methods may be used for quality-control purposes, or for the prediction of the normal strength of concrete at later ages, by the use of an appropriate correlation-curve obtained by testing normally-cured and accelerated cured concrete specimens of the mix proportion and materials to be used at the site. Appendix A of the code contains such case study-based correlation curves
These tests can save rework and, in turn, time and cost in case of strength failure of concrete.
The following two methods of accelerated curing have been covered in this standard:
- Warm-water method
- Boiling-water method.
You can refer to the code for details.
3. IS 9284:1979- Abrasion Resistance Test
Concrete is tough material. But for how long will it sustain in case of constant hammering or vibrations? How do you test that the railway sleepers made of concrete keep the track intact even after passing of thousands of railways passing over them? I.S. 9284: 1979 - Method of Test for Abrasion Resistance of Concrete gives the answer.
The code states, "Abrasion resistance of concrete is one of the measures of its durability. Deterioration of concrete surface may occur due to abrasion by sliding, scraping, percussion or action of abrasive materials carried by water. Therefore, it becomes difficult to ‘assess the abrasion resistance of concrete, as the mode of abrasive action in each case may vary, but evaluation of relative resistance of concrete surfaces is possible."
This standard describes the method of assessing the relative resistance of concrete surfaces by finding the abrasion loss of the specimen subjected to an abrasive charge. The procedure laid down in this standard approximately simulates abrasion under physical effects suffered by concrete pavements ( roads and airfields), industrial floors, railway platforms, dock yards, footpaths, etc. This applies generally for normal weight concrete with a density of 24-26 kN/m3."
This standard covers the determination of abrasion resistance characteristics of concrete under physical effects only by subjecting it to the impingement of air-driven silica-sand using l0 cm concrete cubes.
The Working Principle is as follows: The surface of the concrete cubes is subjected to impingement of an abrasive charge. As a result, abrasion of the concrete surface of the cubes occurs and the resulting loss in mass of the cubes is taken as the abrasion loss of concrete.
4. IS 3085:1965- Check the permeability
Another key aspect of concrete is how it will perform when it comes in contact with water. Will it pass the water through it?
As the code states, "Permeability of cement mortar or concrete is of particular significance in structures which are intended to retain water or which come into contact with water. Permeability is also related to the durability of concrete, especially its resistance, against progressive deterioration under exposure to severe climate, and leaching due to prolonged seepage of water, particularly when it contains aggressive gases or minerals in solution. The determination of the permeability characteristics of mortar and concrete is important."
IS 3085:1965 describes the method of testing for the permeability of cement mortar and concrete, the specimens of which are cast in the laboratory are obtained by cutting out cores from existing structures.
Principle: The test consists in subjecting the mortar or concrete specimen of known dimensions, contained in a specially designed cell, to a known hydrostatic pressure from one side, measuring the quantity of water percolating through it during a given interval of time, and computing the coefficient of permeability. The test permits measurement of the water entering the specimen as well as that escaping it.
What next? Refer to these codes when you need them.
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