Grading of Cement based on American and European Codes

Grading of Cement based on American and European Codes
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In the earlier part of this series (Grades of Ordinary Portland Cement Based on IS Codes), I discussed the grading of Ordinary Portland Cement (OPC) based on Indian Code. OPC is graded differently by the American Society for Testing and Materials (ASTM) and the European Standard. This article talks about the grading system of cement by the two mentioned standards.

Grades of Cement as per American Standard – ASTM C 150

This standard divides Portland cement in eight different types as follows :

TypeI For use when the special properties specified for any other type are not required.
Type IA Air-entraining cement for the same uses as Type I, where air-entrainment is desired.
Type II For general use, more especially when moderate sulfate resistance or moderate heat of hydration is desired.
Type IIA Air-entraining cement for the same uses as Type II, where air-entrainment is desired.
Type III For use when high early strength is desired.
Type IIIA Air-entraining cement for the same use as Type III, where air-entrainment is desired.
Type IV For use when a low heat of hydration is desired.
Type V For use when high sulfate resistance is desired.

Some cements are designated with a combined type classified, indicating that the cements is fulfilling the requirements of both the type of cements and it fit to use for either purpose. Ex: Type I/II.

Air-entraining cement is a special type of cement where air bubbles are intentionally incorporated in the cement by means of special agents. These air bubbles help in providing space for expansion of minute water droplets in concrete due to freezing and thawing action. This protects the concrete from cracking.

Standard Physical Requirement of various cement types

1. Air content of mortar

Air content of mortar in percent volume is 12 for all the cement types except for air-entraining cement. For air-entraining cement, max air content of mortar is 22% and min air content of mortar is 16%.

The code specifically says that the percentage air content indicated here does not ensure that the desired air content will be obtained in concrete.

Code – ASTM C185: Test method for Air Content of Hydraulic Cement Mortar.

2. Fineness

The code specifies two test that can be used to check the fineness of cement – Turbidimeter test and Air permeability test. Though the code gives liberty to the testing laboratories to decide the method of testing, it specifies that the if the sample fails to meet the requirements of air permeability test, the requirements of turbidimeter test will govern.

The code gives the fineness requirement for these two tests in terms of ‘Average Value’ and ‘Any one sample’. ‘Average value’ is the average value of five consecutive samples tested from a source. The value of ‘Any one sample’ indicates result of a test or average of tests performed on one sample.

When tested for fineness by Turbidimeter test, the specific surface of cement in terms of ‘average value’ (min) shall be 160 m²/kg and in terms of ‘any one sample’ (min) shall be 150 m²/kg. This is applicable to all grades of cement except Type III and IIIA. The max value of specific surface of cement in terms of ‘average value’ and ‘any one sample’ shall be 240 m²/kg and 245 m²/kg respectively. The max values are indicated for type II, IIA and IV only.

When tested for fineness by Air Permeability, the specific surface of cement in terms of ‘average value’ (min) shall be 280 m²/kg and in terms of ‘any one sample’ (min) shall be 260 m²/kg. This is applicable to all grades of cement except Type III and IIIA.

The max value of specific surface of cement in terms of ‘average value’ and ‘any one sample’ shall be 420 m²/kg and 430 m²/kg respectively. The max values are indicated for type II, IIA and IV only.

The code
does not specify fineness value for type III and IIIA.

Code – ASTM C115: Test Method for Fineness of Portland Cement by the Turbidimeter.

ASTM C204: Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus

3. Soundness

When test by Autoclave test, unaerated cement shall not have an
expansion of more than 0.8 percent. This is applicable to all grades of cement.

Code – ASTM C151: Test Method for Autoclave Expansion of Hydraulic Cement.

4. Compressive Strength:

The compressive strength requirement of various types of cements as specified by the code is given in the table below.

Cement Type Compressive Strength in MPa
1 day 3 days 7 days 28 days
Type I 12 19
Type IA 10 16
Type II 10 17
Type IIA 8 14
Type III 12 24
Type IIIA 10 19
Type IV 7 17
Type V 8 15 21

Code – ASTM C109/109M: Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube Specimens).

5. Setting Time

When tested by Vicat apparatus method, the setting time of cement
shall conform to the following requirement.

Time of setting shall not be less than 45 mins and shall not be
more than 375 mins. The setting time requirement is applicable to all grades of
cement.

Code – ASTM C191 : Test Methods for Time of Setting of Hydraulic Cement by Vicat Needle.

Grades of Cement as per European Standard – EN-197-1

This code classifies cement in three basic class – Class 32.5,
Class 42.5 and Class 52.5 based on the compressive strength of cement mortar
cube at 28 days.

Mechanical
Requirement of Various Cement Class

1. Compressive Strength

The compressive strength is categorized as mechanical requirement of cement in this code. Based on early strength of cement, each class is divided into two sub-class indicated by N and R.

The class with ordinary early strength is indicated by N and class with high early strength is indicated by R. The compressive strength requirement as specified by the code is given in table below.

Cement Class Compressive Strength (MPa)
Early Strength Standard Strength
2 days 7 days 28 days
32.5 N >/= 16.0 >/= 32.5 upto 52.5
32.5 R >/= 10.0
42.5 N >/= 10.0 >/= 42.5 upto 62.5
42.5 R >/=20.0
52.5 N >/= 20.0 >/= 52.5
52.5 R >/= 30.0

Code – EN 196-1 :  Methods of testing
cement. Determination of strength

Physical
Requirement of Various Cement Class

1. Initial Setting Time

When tested by Vicat apparatus method, the setting time of cement shall conform to the following requirement.

Cement Class Initial Setting Time
(mins)
32.5 >/= 75
42.5 >/= 60
52.5 >/= 45

Code – EN 196-3: Methods of testing cement. Determination of setting times and soundness

2. Soundness

When tested by ‘Le-Chatelier’ method, unaerated cement shall have
an expansion of less than or equal to 10mm. This is applicable to all the
cement class.

Code – EN 196-3: Methods of
testing cement. Determination of setting times and soundness

References:

  1. ASTM C150-07 : Standard Specification for Portland Cement.
  2. EN 197-1 : Composition, specifications and conformity for common cements.
  3. https://theconstructor.org/concrete/air-entrained-cement/23745/



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