Basic On-Site Quality Tests on cement, sand, and aggregate that can be carried out at construction sites without involving complex machinery that all Civil Engineers should be aware of.
The construction quality is largely influenced by the quality of materials applied on the site. The finest structural design is a failure if cement, sand or aggregates are of low quality. Although laboratory testing provides accurate results, field test is fast, cheap, and highly helpful in the daily inspection of the site.
Quality test in Construction
The importance of quality tests in construction.
We shall discuss the importance of field testing construction material before we dive into the individual tests:
- Identify adulteration, or substandard materials.
- Avoid structural flaws and service pandemics.
- Less wastage and rework of material.
- Follow basic IS code recommendations.
- Reduce time and laboratory testing cost.
Quality tests on Cement
The binding material of both concrete and mortar is cement. Low quality of cement may lead to low strength, cracks and failure to last.
1.1 Visual Inspection tests on cement
Purpose: To test freshness and overall quality of cement.
Procedure for tests on cement:
- Observe the color of cement
- It must be grey and with a bit of greenish tone.
- Check for lumps
Observations on cement tests: The presence of lumps implies absorbency. The cement must be smooth and not gritty. Cement that is good does not have hard lumps & One should not take lumpy cement.
1.2 Hand Insertion Tests on cement
Purpose: To test the fineness and moisture content.
Procedure: Take the bag of cement and insert your hand in it.
Observations on cement tests:
- The cement should feel cool
- Warm feeling is a sign of the beginning of hydration.
1.3 Float Tests on cement
Purpose: To determine the fineness of cement.
Procedure: Takes a little amount of cement & drop it on the surface of water.
Observations on cement test: Before sinking, good cement takes a period of time. In case it sinks at once, quality can be low.
1.4 Smell Tests on cement
Purpose: To detect adulteration.
Procedure: Smell the cement sample
Observations: Cement must not be earthy and clay-like in smell. The smell means impurities.
1.5 Check of Packing Date (Very Important) tests on cement
Purpose: To ensure cement freshness.
Key Point: Cement is to be used ideally within 90days of production. Strength reduces with time Age of Cement Reduction in Strength.
- 3 months ~20% loss
- 6 months ~30% loss
- 12 months ~40% loss
Quality Tests on Fine Aggregates–Sand test in the filed
The sand is very important in the workability, strength and durability of concrete and mortar. Sand of bad quality results in cracks, shrinkages, and low strengths.
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Given below are the fine aggregates tests.
2.1 Visual Examination Test
Purpose: To examine purity and dirtiness.
Procedure: Observe sand with naked eyes
Observations: The sand must be clean and without clay, silt and organic material. Contamination is evidenced by the presence of roots, shells or debris.
2.2 Silt Content Test (Bottle Test)
Purpose: To establish percentage of silt in sand.
Procedure: Take a transparent bottle .Fill it with sand up to 1/3 height. Add water and shake thoroughly. Allow it to settle for 3–4 hours
Observations: Sand is covered with a silt layer.
Permissible Limit: The level of silt should not be more than 8 percent of concrete works.Too much silt means the loss of bond.
2.3 Organic Impurities Test
Purpose: To pick up destructive organic matter.
Procedure: The sand is mixed with sodium hydroxide solution. Allow to rest 24 hours.
Observations: The presence of dark brown color implies organic impurities.
2.4 Bulking of Sand Test
Purpose: To ensure rise in volume caused by moistness.
Why It Matters: Bulking has an impact on concrete volume batching.
Procedure: Prepare wet sand in a vessel. Saturated sand to another container. Compare volumes
Observations: Sand may bulk up to 20–30%.Experiencing correct volume when batching.
2.5 Touch Test
Purpose: To check cleanliness.
Procedure: Rub sand between palms
Observations: Clean sand leaves no stain. Clay coats the hands with dirty sand.
Quality Tests on Coarse Aggregates
Concrete contains aggregates, which constitute 60-75 percent of the volume of the concrete. They have a direct impact on compressive strength and durability on their quality.
Given below the coarse aggregate tests
3.1 Visual Shape Test
Purpose: To check particle shape.
Observations: Aggregates ought to be angular or cubical. No flaky and long particles. Flaky aggregates decrease the strength and workability.
3.2 Size Distribution Check
Purpose: To ensure proper grading.
Procedure: Physically examine aggregate sizes. See to it that it is distributed uniformly.
Importance: Incorrect grading amplifies use of cement.
3.3 Cleanliness Test
Purpose: To detect dust and clay.
Procedure: Rub aggregates with hands .Wash sample with water
Observations: Water should not turn muddy
3.4. Aggregate Crushing Test (Field Indication)
Purpose: To test strength (estimated).
Procedure: Between fingers, place aggregate.Try to break manually
Observations: Good aggregates are not supposed to be squashed easily.
3.5 Soundness Test (Simple Field Method)
Purpose: To counter against resistance to weathering.
Procedure: Soak aggregates in water.Dry them in sun repeatedly
Observations: There is no breakage and disintegration, which is a good sign.
3.6 Water Absorption (Site Level) Test.
Purpose: To check porosity.
Procedure: Weigh dry aggregate.Soak for 24 hours.Weigh again
Limit: The absorption of water must not be more than 2%..Even though field tests are valuable, they possess certain drawbacks:
- Inaccurate compared to laboratory tests.
- Unable to establish precise values of strength.
- Only to be taken as preliminary checks.
Always conduct lab tests for:
- Important RCC members
- High-rise structures
- Bridges and heavy load constructions.
Site Engineer Best Practices.
- Materials should always be checked on delivery.
- Keep a material test register.
- Do away with materials which fail simple field tests.
- Keep cement in well-ventilated places.
- Washed sand and aggregates should be used where possible.
Frequently Asked questions (FAQ).
Q1. Are field tests good with cement?
Yes, field testing would be used to determine bad or contaminated cement, however, strength tests had to be done in the lab.
Q2. What is the maximum silt content of sand?
Not more than 8 percent by volume of concrete works.
Q3. Is it possible to use the river sand untested?
No. River sand can have silt and organic contaminations and it has to be checked.
Q4. What is the significance of bulking of sand?
Bulking impacts on volume batching, which causes flawed proportions of mixes.
Conclusion:
Tests on Cement, sand, and aggregate are user-friendly, but potent and cost-effective techniques to maintain the quality of construction on hand. All the site engineers and the contractors must be conversant with these tests in order to prevent structural failure, cost increases, and low workmanship.
Although field tests do not substitute the laboratory tests, they serve as a line of defense in the quality control. Integrating site-level tests with appropriate laboratory tests will guarantee safe, sustainable and cost-effective construction.