**4. Properties and types of cement**

#### **4.1 Physical properties**

Cement used are characteristic by its physical properties, which can control the quality of the cement. Some parameters of good cement are [13]:


### *4.1.1 Fineness of the cement*

Fineness is defined as the particle size of the cement. It is an important factor influencing the cement's rate of hydration. The reaction between cement and water occurs only at the surface of the solid particles, thus the accumulation of large particles on the surface of unreacted material could hinder the overall reaction.

The required fineness of good cement is achieved during the cement manufacturing process by grinding the clinker, with the most common method used for both controlling the grinding process and testing the finished cement [14].

One method is to measure the surface area per unit weight of cement by determining the rate of passage of air through a bed of cement [15].

#### *4.1.2 Soundness of the cement*

Soundness is defined as the immunity of cement to shrinking upon hardening. After the cement has set, it must not undergo any noticeable expansion, which can be caused by the presence of too much hard-burned free lime and magnesia. After setting, a good cement retains its volume without any deferred expansion.

Unsoundness in cement may appear after several years, so tests must be performed to ensure soundness and determine the possibility of this risk occurring [16].

• Le-Chatelier test

This method examines the expansion of cement caused by undesired excess lime. Cement paste is sandwiched between two glass plates and immersed in water for 24 hours at room temperature. It is then removed to measure the distance between the indicators before being returned to the water and boiled for at least an hour. The space between indicator points is measured again after the device has cooled. This distance should not be greater than 10 mm in a good-quality cement [17].

#### • Autoclave test

In this test, the cement paste is placed in an autoclave device (high-pressure steam vessel) to be cured. The pressure is slowly brought to about 2 MPa, and the temperature increased to 210°C. The past is then kept in the autoclave for three hours. After bringing the autoclave to room temperature and pressure gradually, the specimen's length change is measured and expressed as a percentage. A maximum

*Characterizations of Cement and Modern Sustainable Concrete Incorporating Different Waste… DOI: http://dx.doi.org/10.5772/intechopen.100447*

**Figure 1.** *Le-Chatelier apparatus [18].*

of 0.8 percent autoclave expansion is required for good-quality cement according to the American Society for Testing and Materials (ASTM) (**Figure 1**) [17].

#### *4.1.3 Consistency of cement*

Consistence is the minimum amount of water required to complete the chemical reaction between water and the cementation material.

Determining standard consistency of cement is essential because if less water is added than the standard consistency would not complete chemical reaction and more water would increase water-cement ratio in either two cases will result in the reduction in strength**.** A Vicat apparatus is used to obtain the correct consistency of cement.

#### • Vicat test

The Vicat apparatus is loaded with cement paste and the plunger of the apparatus is lowered until it touches the top surface of the cement. The plunger, which has a length of about 50 mm and a diameter of about 10 mm, will penetrate the cement to a certain depth depending on its consistency. When the needle penetrates 10 mm into a cement, it is said that the cement has a normal consistency.

To obtain a standard or normal consistency of cement, only 25–35% water by weight of cement should be added (**Figure 2**) [19, 20].

#### *4.1.4 Setting time of the cement*

When water is added to cement, it hardens and sets. This period can vary according to several factors, including cement fineness, chemical content, cement– water ratio, and admixtures. Setting time could also be used to predict hydration rate. There are two important setting times that can be measured:

Initial setting time is the time it takes for the cement paste to lose its plasticity as soon as the water is added to cement.

Final setting time is the time taken for the cement to harden and completely lose its plasticity and be able to sustain some small loads.

A Vicat test can also be used to measure and test the setting time of the cement according to ASTM guidelines [20].

**Figure 2.** *Vicat apparatus [18].*
