1) Consistency Test
(Unit-%) – Consistency test is performed on Vicat Apparatus of 40mm depth. Consistency of cement is defined as the amount of water required in % by weight of cement to penetrate the 10 mm plunger to a depth of 33-35 mm from top or 5-7 mm from bottom in gauge time 3-5 minutes.
- The range of consistency of cement is 25-35%.
2) Initial Setting Time (Dormant period)
(Unit-minutes) (Temperature 27 +/- 2 degree and 90% Relative Humidity) Cement paste is prepared by adding 0.85 times the water required to give a paste of standard consistency and Vicat apparatus is used with a needle having a diameter of 1 mm. initial setting time is the time required to harden the cement paste such that the needle penetrates up to from the top or 5mm(+/-) 0.5mm from the bottom. The initial setting time is the time when cement paste starts losing its plasticity. It is the endpoint when the wet mix can’t be molded into shape. (the maximum temperature at the final setting).
Read More———————— Types of Cement
3) Final Setting Time
(Unit- minutes/Hours) (Temperature 27 +/- 2 degree and 90% Relative Humidity) Same cement paste, as used in the initial setting, it is the period elapsing between the time, water is added to the cement and the time, the needle makes an impression on the surface of the text block, while the attachment fails to i.e. plunger fails to make an impression. It is the time the paste lost its plasticity.
Initial setting time for ordinary portland cement (OPC) should not be less than 30 minutes but for low heat cement the initial setting time is 60 minutes and the Final setting time for OPC and Low heat cement should not be more than 600 minutes.
4) Strength Test
Compressive Strength Mix is prepared of Ennore sand (special sand from Ennore, Tamil Nadu) and
cement in the ratio of 3:1 and quantity of water added is % of (Cement + Sand)
(Where w is the consistency of cement ). The mix is placed in a mold of cube size 7.06cm and Area = 50cm2
The compressive strength is calculated after 28 days of curing the cube. Commonly available cement is of Grade 43, 53, 63. Grade 43 means indicates the compression strength of the cement concrete after 28 days of setting. 43 Grade Cement attains compression strength of 43 mpa (megapascals) in 28 days of setting compared to 53 mpa attained by 53 Grade cement.
- 53 Grade cement is used for fast-paced construction where initial strength is to be achieved quickly. 53 Grade cement has a fast setting compared to 43-grade cement. 53 Grade attains 27 mpa in 7 days compared to 23 mpa by 43-grade cement.
- 3 Grade OPC cement is Used in RCC and pre-stressed concrete of higher grades, cement grouts, instant plugging mortars, etc. where initial higher strength is the criteria. 43 Grade OPC Cement is commonly used for plastering works, Non-RCC structures, pathways, etc where initial setting time is not of importance.
The mortar of cement and sand is prepared. The proportion is 1:3 which means that (x) gm of cement is mixed with 3(x) gm of sand, The water is added to the mortar. The quantity of water is the percent by weight of cement and sand. The mortar is placed in briquette molds.
- The cross-sectional area of the briquette at its least section is 6.45 cm2. Hence the ultimate tensile stress of cement paste is obtained from the following relation: Ultimate tensile stress = failing load / 6.45
- The tensile stress at the end of 3 days should not be less than 20 kg/cm2 or 2 N/mm2 and that at the end of 7 days should not be less than 25 kg/cm2 or 2.50 N/mm2.
- The tensile strength of cement mortar is 10% of the compressive strength of cement mortar.
Specific Gravity of Cement
Le Chatelier Flask to determine Specific gravity of cement.(G=3.15 approx)
W1 is empty weight of flask, W2 is empty weight+ Cement, W3 = Weight of flask+ cement + Kerosene, W4 is weight of flak+ full-filled kerosene.
5) Soundness Test
(Unit –mm) IS-4031, Soundness means the ability to resist volume expansion. For checking excessive expansion due to excess of lime(CaO), gypsum, and magnesia (MgO )(>6% ). The maximum allowable expansion 10mm, for high alumina cement and super sulphate it is 5mm.
Water used in soundness test is
- Le-chatelier test for checking soundness of free lime only. (expansion is measured when cement paste, is placed in boiling water for 3 hour, after 24hour setting)
- Auto-clave test is used for checking soundness due to unburn magnesia and Lime both. (Allowable limit 0.8%, for all cement) (Autoclave test is done when Magnesia is more than 3%)
Watch Video ——————– Types of Mortar
6) Fineness Test
(Unit –cm2 /gm) the fineness of cement is responsible for the rate of hydration and hence the rate of gain of strength and also the rate of evolution of heat, Increase in fineness of cement also increases the drying shrinkage of concrete and hence creates cracks in structures.
a) Air permeability method unit ( ⁄ ) (IS 269)
b) Wagner Turbidimeter
c) Nitrogen Abortion method.
d) Dry sieving (IS 4031)
Fineness of OPC is 2250cm2 /gm and rapid hardening cement is 3250cm2 /gm
7) Heat of Hydration
1 gm of cement liberates 90 caloriess of heat in 7 days and 100 calories in 28 days.
a) Vacuum Flash ( Short test, result in few days)
b) Adiabatic calorimeter ( Longer period test)