QUALITY CONTROL OF CONSTRUCTION MATERIALS (Cement) by K. RAMESH Research Officer, Engineering Materials Laboratory, A.P. Engineering Research Laboratories, Himayatsagar, HYDERABAD

Tests on cement (Physical Tests) Standard consistency Setting times (Initial and Final ) Compressive strength Fineness Soundness Specific Gravity

Standard consistancy Standard consistancy of cement may be defined as the percentage of water (by weight of cement), to be mixed with the cement, to get a cement paste having some stiffness, which is arbitrarily fixed with the help of Vicat apparatus.

Name of the Test: Standard Consistency of Cement. [ IS : 4031 (Part.4) – 1988] 1.Weight of cement (A)=500 g. 2.Observations: S.No. Weight of water (g) Plunger penetration (mm) Weight of water in g for Standard consistency (B)= (Note:For standard consistency the depth of Penetration of vicat plunger should be 5 mm to 7 mm.) 4.Standard consistency in % (P)= B/A * 100= =

Setting times The time at which the cement paste looses its plasticity is termed as initial setting time and the time at which the cement paste becomes hard mass is termed as the final setting time.

Name of the Test: Setting Times of Cement. [ IS : 4031 (Part.5) – 1988] 1.Standard Consistency in % (P)= 2.Weight of cement (A)= 500 g 3.Weight of water in g = 0.85 x P/100 x A = = 4.Starting time (B)= 5.Time at initial setting (C)= (Note: The period elapsing between the time when water is added to the cement and the time at which the vicat needle fails to pierce the test block by 5mm + 0.5mm is termed as the initial setting time.) 6.Time at final setting (D)= (Note: The period elapsing between the time when water is added to the cement and the time at which the vicat needle makes an impression on the surface of the test block while the annular ring fails to do so, is termed as the final setting time.) 7.Initial setting time in min = C – B = 8.Final setting time in min = D – B =

I.S. Requirements for setting times of cement 1. Initial setting time in minutes Not less than Final setting time in minutes Not more than 600

Compressive strength Size of the cube = 7.06 Cm. Cement Mortar = 1 : 3 Ages = 3, 7, 28 days No. of cubes = 3 x 3 = 9 Weight of cement = 200 g Weight of Ennore sand = 600 g Weight of water = (P/4 + 3) % where P = Standard consistancy of cement

Name of the Test: Compressive Strength of Cement. [ IS : 4031 (Part.6) ] 1.Weight of cement for each cube of 7.06 Cm size=200 g 2.Weight of I.S. sand =600 g (Consisting of three grades, each of 200 g) 3.Standard consistency of cement in %(P)= 4.Weight of water in g= (P/4 + 3) x 800 / 100= = 1.Compressive strength: a. Cross sectional area of the 7.06 Cm cube (A)= 50 Cm 2 b. Observations: S.No. Age of testing (days) Compressive Load (Kg) Average Compressive Load (Kg) P=(P 1 +P 2 +P 3 )/3 Average Compressive Strength (N/mm 2 ) =(P/A)/ P1=P1= P2=P2= P3=P3= 2.7 P1=P1= P2=P2= P3=P3= 3.28 P1=P1= P2=P2= P3=P3= (Note: For each age of testing minimum 3 cubes shall be tested.)

I.S. Requirements for compressive strength of cement Compressive strength in N/Sq.mm at the age of IS: Grade IS: Grade IS: Grade a) 3 days16 minimum23 minimum27 minimum b) 7 days22 minimum 33 minimum 37 minimum c) 28 days33 minimum 43 minimum 53 minimum

Fineness Fineness of cement is a measure of the mean size of the cement grains. The rate of strength development of cement depends on the rate of hydration of cement which inturn depends on the fineness of cement.

Name of the Test: Fineness of Cement. [ IS : 4031 (Part.2) ] 1.Specific gravity of cement(  ) = 2.Weight of cement in g=  x V (1 – e) = = Where, V = Bulk volume of bed of cement in Cm 3 = 1.89 e = Desired porosity of bed of cement= Time required for fall of 5 Cm height in sec (T) (Average of 3 readings) = (T 1 +T 2 +T 3 ) / 3 = = 4.Fineness in m 2 /Kg=  T /  = =

I.S. Requirements for fineness of cement Particulars of testFor OPCFor PPC Fineness in Sq.m/KgNot less than 225Not less than 300

Fineness (cm 2 /gm) Compressive strength at the age of (N/mm 2 ) 7 days28 days90 days1 year

Soundness Certain cements undergo large expansion after setting causing disruption of the set and hardened mass. Unsoundness in cement is due to excess lime or excess magnesia in cement Unsoundness in cement due to excess lime is detected by the Lechatelier test. Unsoundness in cement due to excess magnesia & excess lime is detected by the Autoclave test.

I.S. Requirements for Soundness of cement 1. Expansion by Lechatelier test in mm Not more than % Increase in length by Autoclave test Not more than 0.8

Specific gravity Specific gravity of cement may by defined as the weight of cement to the weight of equal volume of water. It is determined by using Lechatelier flask or 50ml specific gravity bottle.

Name of the Test: Specific Gravity of Cement. [ IS : 4031 – 1988] 1.Weight of specific gravity bottle in g (W 1 ) = 2.Weight of specific gravity bottle with about half filled cement in g (W 2 ) = 3.Weight of specific gravity bottle with about half filled cement & rest is filled with kerosene iin g.(W 3 ) = 4.Weight of specific gravity bottle completely filled with kerosene in g (W 4 ) = 5.Specific gravity of cement (  ) (W 2 - W 1 ) = x 0.79 (W 4 - W 1 ) - (W 3 - W 2 ) = (Note : Specific gravity of kerosene is taken as 0.79)