Cement Test - Field And Laboratory Test

What are the Different Types of Cement Tests?

Cement Testing Methods are used to determine cement's qualities, including its specific gravity, strength, fineness, consistency, etc. Before using a material in a construction project, it must be tested.

This article will discuss different types of cement tests based on their physical and chemical properties. These test of cement are further divided into two categories-

• Field Test of cement
• Laboratory Test of cement

Field Test Of Cement

In a field test of cement, generally, we take ordinary portland cement to determine its properties of cement. Field tests are generally examined based on cement's physical touch and feel. Some points are discussed below for a field cement test.

• Cement is always free from lumps and should be homogeneous throughout the bag.
• The color of cement should always be greenish gray.
• When putting your hand into the bag of cement, it should feel cool.
• A pinch of cement between two fingers always makes the cement texture smooth and soft.
• When a small amount of cement is taken and thrown into any water container, the cement particle does not sink immediately; it should float for some time and then sink.

Laboratory Test of Cement

In laboratory test of cement, samples should be taken from 12 different bags or from 12 different heap points. Laboratory cement tests generally consider its chemical properties, fineness, consistency, initial setting time and final setting time, soundness, specific gravity, the heat of hydration, and strength determination. Some of these are explained below.

Fineness Test of Cement

To find the mean diameter of cement particles, known as the fineness test of cement. This is done by -

(i) Sieve method - In this 100 gm of sample and 90-micron sieve is used to measure grain size of cement particles and by the help of mechanical shaker, this is shaken for 15min.

(ii) Air permeability method- This method works on the specific surface area measurement by using Nurse & Blaines apparatus. The specific surface area depends on the cement type used in the cement test.

Table: Minimum specific area basis on types of cement

(iii) Wagner turbidimeter method- This method also works on specific surface area measurements.

Consistency Test of Cement

To find the fluidity of cement paste after adding the water to the cement, the method is called as consistency test of cement. These types of cement tests are done to prepare cement paste 30% water is required, but it varies on different types of cement.

To find the consistency of cement Vicat apparatus is used, which will indicate the penetration of the plunger in cement paste mold is upto 5 mm to 7 mm from the bottom and 33 mm to 35 mm from the top of the Vicat's apparatus.

To perform Vicats apparatus test for consistency, some parameters should be maintained, such as humidity of 90%, room temperature 27⁰C, etc.

Setting Time Test of Cement

After some time, the cement paste becomes stiff. This stiffness is measured in terms of setting time. For this cement test, 0.85P water is mixed in cement where P is the standard consistency of cement paste. This is classified into two categories as-.

• Initial setting time-With the help of Vicat's apparatus, this cement test is performed in the laboratory. In place of a plunger, a 1.13mm dia needle is attached to Vicat's apparatus. This needle is free fall into the cement paste mold by self-weight; this penetration occurs upto 35 mm from the top and is considered the initial cement setting time. Generally, it is 30min for OPC and varies with types of cement.
• Final setting time- This type of cement test is also done by Vicat's apparatus by using a collar in place of a 1.13 mm needle. The collar diameter is 5mm. When the collar free falls from Vicat's apparatus and touches the surface of cement paste mold but doesn't penetrate or not put marks over the surface of cement mold considered as final setting time. Generally, it is taken 10 hours for OPC but varies with the type of cement.

Table: Setting time basis on types of cement.

Soundness Test of Cement

This cement test is done after the initial setting time because, after the initial setting time, expansion of cement has occurred, and this test measures the volume change due to expansion. For the soundness test of cement, we consider 0.78P consistency, where P is the standard consistency of water.

The soundness test of cement is done by two methods-

• Autoclave method - In this method, the expansion of cement due to lime and magnesia is measured. The autoclave mold dimension is 25mm x 25mm x 282mm and this result comes into %. Generally, it comes at a maximum of 0.8%. For this cement test, we take a 25mm diameter sample put in an autoclave apparatus for 1 to 1.25hours under the pressure of 21kh/cm².
• Le-Chatelier method- In this method unsoundness test of cement is due to only free lime. The le-chatelier test sample is 100 gm of cement with 0.78P water consistency. For this test, expansion of cement is a maximum of 10 mm for ordinary portland cement, rapid hardening cement, low heat cement, and portland pozzolana cement.

Strength Test of Cement

This cement test is done to find cement's tensile or compressive strength. We take a 1:3 (cement: sand) sample to measure cement's strength. This type of cement test is classified as.

1. Tensile strength test of cement- In this cement test method, humidity of 90%, room temperature 27⁰C should be maintained, and water consistency is taken (0.2P+2.5%) of the combined weight of cement and sand and where P is the standard consistency. Briquette test apparatus is used where the test apparatus across-sectional area is 6.45 cm², and a minimum of 6 test samples are used.

In general ordinary portland cement, tensile strength should not be less than 2 N/mm² for 3 days and 2.5 N/mm²for 7 days. OPC cement tensile strength is considered 10-15% of compressive strength in this cement test. In this cement test, the applicable rate of loading is 1.2 to 2.4 N/mm²/min.

2. Compressive strength test of cement- In this cement test method, humidity of 90%, room temperature 27⁰C should be maintained, and water consistency is taken (0.25P+2.5%) of the combined weight of cement and sand and where P is the standard consistency.

The compressive strength test on the cement sample is taken as 7.06 cm³, or the cross-section area of the sample is considered to be approximately 50 cm².

In general ordinary portland cement and portland pozzolana cement have a minimum of 3 days of compressive strength of 16 N/mm2, and for 7 days, compressive strength of 22 N/mm². For this, to prepare the sample, cement and sand are taken at 185gm (approx.200 gm) and 555 gm (approx.) 600 gm, respectively. In this test, the applicable loading rate is 35 N/mm²/min, and a minimum of 3 samples are taken for this test.

Specific Gravity of Cement Test

This cement test is also done with the help of the Le-Chateliers flask apparatus. In this test of cement specific gravity of ordinary portland cement is 3.15, which is heavier than water; that's by when cement particles sink in water. Specific gravity depends on the behavior of the cement particle. In this way, we consider its optimum range as 3.1 to 3.16.

Heat of Hydration Test of Cement

This cement test is also done to control the temperature of the structure. In this test, when cement is mixed with water heat is generated, and this heat reaches 50⁰C temperature. The components responsible for this temperature rising are alite, belite, celite and felite.

These components are used in the proportions as per demanding the structures as heavy structures are using low heat cement or rapid construction work needed earlier strength hence those components are responsible for the early and slow gaining strength by their heat realinsing capacity.

Chemical Composition Test of Cement

This cement test signifies the different component limits in the mixture of cement. Many types of chemicals are used in cement formation, and their certain limits allow the appropriate strength to the cement. Some of these are should be in limit as.

• The weight of magnesia should be less than 5% of the total weight.
• Total sulfur should be less than 2.75%.
• The total lime saturation factor should be in the range of 0.66 to 1.02.
• Total alumina should be 66% of iron. etc.