The definition of specific gravity involves the comparison between the weight of a particular substance and an equal volume of water. For Portland cement, the specific gravity value is typically around 3.15. However, this value changes for Portland pozzolan cements and Portland blast furnace cements, which have a value close to 2.90. This information comes from the Portland Cement Association (PCA) in 1988.
To determine the specific gravity of cement, kerosene is used as it does not react with the cement.
Significance of Specific Gravity of Cement
The specific gravity of cement can be affected by its moisture content, which can cause an increase or decrease in its value. This is because cement particles have pores or particles that can hold water. A nominal mix, which is used in construction, requires cement with a specific gravity of 3.15, so any changes in this value can affect the mix design. To ensure the quality of the mix, it is crucial to test the specific gravity of the cement before starting the mixing process.
Due to the impact of moisture content on specific gravity, it is not advisable to use old stock cement in construction. Old stock cement may have been exposed to external moisture, which can affect its specific gravity. If the specific gravity of cement is greater than 3.19, it indicates that the cement was not finely minced during production or has a high moisture content. The presence of moisture content in cement is often identified by the presence of chunks in the cement. Therefore, it is crucial to check the specific gravity of cement to ensure its quality and suitability for use in construction projects.
Specific Gravity Test on Cement
Equipment and Apparatus
The experiment involves the use of a Le Chatelier’s flask and a weighing balance, along with kerosene that is guaranteed to be free from water. The Le Chatelier’s flask is a glass container used to study the effects of various factors on chemical equilibria. Meanwhile, the weighing balance is a tool used to measure the mass of objects with great accuracy. The kerosene used in the experiment has been specifically chosen for its lack of water content.
Fig.1: Specific Gravity of Cement Test Apparatus
The “Le Chaterlier’s flask” is a specialized glass flask used for chemical experiments. It is composed of thin glass and has a bulb at the bottom, which can hold up to 250 ml of liquid. The bulb has a mean diameter of 7.8 cm, and the stem is graduated in millimeters. The zero graduation point is located at a distance of 8.8 cm from the top of the bulb.
At a distance of 2 cm from the zero point, there is another smaller bulb with a length of 3.5 cm and a capacity of 17 ml. Additionally, the stem is marked with 18 ml at a distance of 1 cm from the bulb and is graduated up to 24 ml. The portion of the stem above the 24 ml mark is in the form of a funnel with a diameter of 5 cm.
Overall, the Le Chaterlier’s flask is designed to allow for precise measurement and control of liquid volumes in chemical experiments. Its unique design allows for the manipulation of chemical reactions by altering the amounts of reactants and products present in the flask.
Procedure for Specific Gravity Test on Cement
In the given procedure, a flask is used and it is first allowed to dry completely to ensure that there is no liquid or moisture present. The weight of the empty flask is then measured and recorded as W1.
Next, a bottle is filled with approximately 50gm of cement, which corresponds to half of the bottle’s capacity, and closed with a stopper. The weight of the arrangement including the stopper is measured and recorded as W2.
To the bottle containing cement, kerosene is added until the top of the bottle is reached. The mixture is then thoroughly mixed to remove any air bubbles. The flask is then filled with this mixture, along with the stoppered bottle, and the entire arrangement is weighed and recorded as W3.
The flask is then emptied and filled to the top with kerosene. The arrangement is weighed again and recorded as W4.
Observations and Calculations
The Specific Gravity (SG) of cement is an important physical property that helps determine the quality and consistency of cement used in construction. It is defined as the ratio of the density of cement to the density of water at a specific temperature and pressure.
The formula used to calculate the specific gravity of cement is:
SG = Density of Cement / Density of Water at a specific temperature and pressure
This formula takes into account the fact that the density of water can change depending on the temperature and pressure at which it is measured. By comparing the density of cement to the density of water at the same temperature and pressure, the specific gravity of cement can be calculated.
The specific gravity of cement is an important factor in determining its strength and durability, as well as its suitability for different applications. It is typically measured using a pycnometer, which is a specialized instrument designed to accurately measure the volume and density of materials.
In summary, the specific gravity of cement is a crucial physical property that can be calculated using the formula SG = Density of Cement / Density of Water at a specific temperature and pressure. This value can help determine the quality and suitability of cement for different construction applications.
The specific gravity of kerosene is given as 0.79g/cc. It is important to note that duplicate determination of specific gravity should agree within 0.01 to ensure accuracy in the measurement. In order to obtain precise and reliable results, it is essential to maintain a constant temperature of the flask before each reading is taken. Therefore, proper care should be taken to ensure that the flask is held at a consistent temperature throughout the measurement process. This will help to eliminate any potential sources of error and ensure that the specific gravity of kerosene is accurately determined.
Result
The specific gravity of a sample of cement =