Cement properties can be categorized into two types. Chemical properties and Physical properties. For quality controlling purpose of concrete or cementing materials, chemical properties are normally ignored and physical properties are taken into consideration. In this post we are going to share physical properties of Portland cement.
Physical Properties of Portland Cement
- Setting Time
- Compressive Strength
- Heat of Hydration, and
- Specific Gravity.
Fineness of cement means the particles size of cement. It affects the hydration process of cement. That means it affects the rate of strength gain of cement.
Cement has a trend to shrink when it is hardened. This is called soundness of cement. Good soundness cement doesn’t shrink after hardening.
Consistency means the required water to produce plastic cement paste for particular cement. Thus one can know the water-cement ratio for better workability of mix.
As soon as water is mixed with Portland cement, hydration process starts and it begins to set. Cement has two setting time, initial-setting time and final-setting time. In construction, initial-setting time shouldn’t be too early and final-setting time shouldn’t be too late. Normally, initial-setting time is 30 to 45 minutes and final-setting time is below 10 hours.
Cement has three types of strengths. Compressive strength, Tensile strength and Flexural strength. However, compressive strength is taken into consideration, the rest can be ignored. For knowing compressive strength of cement, Only cement paste can’t be tested. For this purpose, either cement-sand mortar cubes or”cement-concrete cubes” are made. The testing result of cubes can be affected by several things such as water-cement ratio, curing and dampness of cubes during testing. Minimum compressive strength result for 3 days mortar cube should be 16 N/mm2 and for 7 days cube should be 22 N/mm2.
Heat of Hydration
Cement reacts as soon as the water is added. It is called hydration. During hydration cement generates heat. This is the Heat of Hydration. Heat of Hydration is influenced by several things. Such as Cement’s ingredients, fineness of cement and water-cement ratio, etc. During large volume concreting cement creates much heat in the center of concrete structure. This extreme heat can affect the quality of concrete. On the other hand, Heat of Hydration can be helpful during cold weather concreting.
Specific Gravity of cement is necessary for calculating the mass for desired volume of cement. The Specific Gravity of normal type of cement is 3.15.
Which cement property/properties do you consider most when choosing cement for you structure?