Top 5 Physical Properties of Cement

The important physical properties of cement are fineness, setting time, soundness, standard consistency, and compressive strength. A good quality cement must be uniform in color and free from lumps. When taken in hand, the cement must be cool. Quality cement, when thrown in small amounts into the water must sink.

Fig.1. Cement; Image Courtesy: www.lehighhanson.com

We will discuss the physical properties one by one:

1. Fineness of Cement

Fineness is the measure of the mean size of the grains in a cement sample. If the grain size is less, the surface area will be more for a specified quantity of cement. The rate of hydration and hence the strength attainment is more for a finer cement but shrinkage is high.

Fineness is measured by sieve test or air permeability test. For good quality cement, the residue left after sieving through 90 microns sieve should not exceed ten percent of the weight for sieve test and the specific surface should not be less than 2250 cm2/gm for permeability test.

                 Read ＞＞ Structure of Hydrated Cement Paste (HCP)

2. Setting Time of Cement

The process of changing the cement paste to a hard solid mass is known as the setting. The setting time can be the initial setting time or final setting time. The time at which the cement paste loses its plasticity after the addition of water is known as initial setting time.

It must be sufficient to allow time for mixing, transporting and placing the cement paste. The initial setting time should not be less than 30 minutes for ordinary portland cement. The time elapsed between the moment water is added to the cement and the time when the paste has completely lost its plasticity and has attained sufficient firmness to resist certain definite pressure is called as final setting time. The final setting time must not be more than 60 minutes.

3. Soundness of Cement

Soundness is the property of the cement that makes the cement not to undergo a volume change in large amount after the setting process. The cement that is not sound will result in the cracking and disintegration process.Volume change in cement is caused due to excess lime and magnesia. 

Soundness is measured by means of Le Chatelier's apparatus. The expansion measured in volume for ordinary portland cement must not exceed 10mm.

4. Standard Consistency of Cement

Standard Consistency is a parameter used to measure the setting time and the soundness of the cement. Standard Consistency is defined as the quantity of water required to produce a workable cement paste. This is determined by the Vicat Apparatus. The value of standard consistency ranges from 25 to 35 percent of the dry weight of the cement.

5. Compressive Strength of Cement

It is defined as the characteristic compressive strength at 28 days of curing of a cement mortar cube of 50 cm3 face area prepared in the ratio of 1:3 by adding (p/4 + 3)%  of water, where p is the standard consistency. 

The test is determined by using the compressive testing machine. For OPC the compressive strength must not be less than 33 N/mm2 at 28 days of curing.

Read ＞＞ Hydration of Cement - Stages of Hydration Reaction