Compressive strength test for cement

COMPRESSIVE STRENGTH TEST

OBJECT

               To determine the compressive strength.

APPARATUS

            Compressive strength testing machine, Mould size 7.06 cm´ 7.06 cm´ 7.06 cm, Temping steel rod 0.6 m long and 16 mm in diameter, Steel pan for mixing the cement.

MATERIAL:- Sample of cement, standard sand.

             

                                     Fig:- Compression testing machine (2000 KN)

PROCEDURE

1. Take 185 gm sieved cement and 555 gm standard sand by weight  (cement-sand ratio is 1:3).
2. Take p/4+3.0 percent of water in case of standard sand and p/4+3.5 percent in case of ordinary sand.
3. Mix cement and sand properly in a non-porous mixing pan. Add water to the mixture and mix until the color of cement mortar reaches uniformly. The mixing time should not be more than 5 min.
4. The mixture is filled in the cubic mould in three layers. Each layer is compacted with temping rod.
5. Mould is kept in damp condition for 24 hrs.
6. Now, the cement block is released from the mould and immersed in a water tank.
7. After 3 days, 7 days and 28 days the compressive strength of cement is tested by using the compressive strength-testing machine.

                     Table:- Compressive strength at 7 days of cement

s.no.	size, cm	area cm2	load, kg	comp. st.	avg. st.  KG/CM2
1	7.05*7.05	49.98	10500	210.06
2	7.05*7.05	49.98	10400	208.06	242.74
3	7.05*7.05	49.98	15500	310.09

CALCULATION

 Compressive strength = P/A
Where,

P=Maximum load applied to the cube. (N)

A=Cross sectional area (Calculated from the mean dimensions) (mm²)

§  Compressive strength is reported to the nearest 0.5 N/mm².

§  Specimens that are manifestly faulty, or that give strengths differing by more than 10% from the average value of all the test specimen should not be considered.

§  Test three cubes for compressive strength for each period of curing.

RESULT

                Compressive strength is 242.7 kg/cm²  at 7 days.

PRECAUTIONS

§  The mould should be oiled before use

§  The weighing should be done accurately

§  The temperature and humidity must be accurately controlled

§  Increase the load gradually during testing.

§  The cubes should be tested immediately after taking out of water and not allowed to dry until they fail under testing.

§  The gauging time should be strictly observed.

§  The cubes should be tested on their sides and not on their faces.