The soundness of the cement is the ability to resist volume changes after hardening. The soundness test on cement is significant because,using unsound cement leads to cracks and hamper the structural quality. A sound cement is one of the key materials used in construction. Therefore it is essential to determine its quality before using it in construction.
Cement tests – Categories
Cement is one of the oldest and most used binding materials and an integral ingredient used in the construction sector. The quality, serviceability, and stability of a structure are directly related to the quality of cement used in it. Hence it is necessary to analyse the quality of cement before using it for works. The tests for determining cement quality are split into two major categories.
- Laboratory test
- Field tests for cement
Field tests on Cement
The quality of cement is determined using some simple field tests. These tests do not require any sophisticated types of equipment and professional skills and get the results very quickly. By conducting these simple tests and analyzing the results we will get an idea about the cement quality and can immediately decide on accepting or rejecting it.
Following are the common field tests conducted to ensure the quality of cement
These are first look tests and the quality of cement is ensured by its smoothness to touch, the colour of cement, etc.
- Checking manufacturing date
- Visual checking of lumps
- Feel test
- Heat of cement
- Water float test
- Setting test
These basic tests give an approximate characteristic of cement. These are easy and quick but not accurate, however help in concluding the acceptance of cement for works.
Laboratory tests for Cement
The laboratory tests defines the physical and chemical properties of cement. It is not possible to check all the cement properties at the site. The main laboratory tests conducted on cement is as follows.
- Fineness Test
- Compressive Strength Test
- Consistency Test on cement
- Setting time
- Soundness Test
- Tensile strength Test
- Heat of hydration
Lab tests require time. But it provides accurate results. In this article, we are going to describe the Soundness test on cement.
Soundness test of cement
The soundness of the cement is the ability to resist volume changes after hardening. The soundness test on cement is significant because usage of unsound cement leads to cracks and hamper the structural quality.
The chemical composition of cement consists of lime. About 60 to 70% of cement is lime. The main function of lime is to help cement in the setting process. A good quality cement do not change its volume after hardening. Following are the reasons for the unsoundness of cement.
- If the cement has an excess amount of lime, expansion or contraction in volume occurs after setting.
- Another reason for unsoundness is the inadequate burning of cement. This leads to cracks, disintegration and a decrease in durability.
- Improper grinding and mixing of raw materials during the manufacturing process of cement.
- Due to the high proportion of magnesium content or sulphate content.
Therefore Soundness test is performed to determine whether the cement shows volume changes or not.
Relevant IS code for soundness test of cement
- IS 4031 (Part 3)-1988
- ASTM C 151-09
- BS EN 196-3: 2005
Soundness of cement is calculated by using Le-chatelier’s apparatus.
- Le-Chatelier mould
- Water bath
- Vernier Calliper
- Pan and trowel
Le-chatelier mould is made using brass. It consists of a spring-tensioned split cylinder and an indicating long arm in its either side. The internal diameter and height of the cylinder are 30mm and 30mm. The size of glass plates is 50mm x 50 mm. For each test, we need three such moulds. The test should be performed at a temperature of 27 ± 2°C and relative humidity of 50 to 80 per cent as per IS code.
Procedure for soundness test on Cement
Before Performing the test, calculate the standard consistency of cement to find out the water required to obtain the normal consistency(P).
- Take about 100 gm of cement and add 0.78-times the water needed to make cement paste with normal consistency.
- Then grease the glass plate and the Le-chatelier mould to avoid the sticking of cement on its surface.
- Fill the cement paste and strike out the excess cement using a trowel.
- Cover the mould with another glass plate and place a weight above the glass plate.
- Then immerse the whole assembly inside the water bath for 24 hours.
- After 24 hours, take out the mould from water and measure the distance between the indicators.
- Note this measurement as L1. After that place, the assembly in the water bath
- Boil the water for 25 to 30 minutes and leave them for 3 hours.
- After that, allow them to cool till it reaches the room temperature.
- Now take out the assembly and measure the distance between the indicators and mark them as L2.
Volume expansion of cement = L1 – L2
L1 is the distance between the indicators after immersing in water for 24 hours
L2 is the distance between the indicators after immersing in water at boiling temperature for 3 hours
This value differs for different types of cement. The expansion of volume for Ordinary portland cement, portland pozzolanic cement, low heat cement and rapid hardening cement should not exceed 10mm. For high alumina cement, super sulphate cement, the volume expansion should not exceed 5mm. Because it contains excess lime or magnesium which is not suitable for construction.