Federal Aviation

Administration

Memorandum

Date: February 7, 2023

To: All Airports Regional Division Managers

From: Michael A.P. Meyers, P.E. 

Manager, Airports Engineering Division, AAS-100

Through: Alberto Cruz, Manager, Design and Construction Branch, AAS-110 

Prepared by: Harold Honey, Civil Engineer, Design and Construction, AAS-110

Subject: Engineering Brief No. 106, Guidance for the Implementation of Changes in 

Industry Cement Standard Specifications

This Engineering Brief (EB) provides interim guidance on the specification of cements to be 

used with construction of airfield pavements (cement treated subgrade, stabilized subbase, 

stabilized base, rigid pavement, and concrete for miscellaneous structures).

Attachment
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EB No. #106 FAA Airport Engineering Division Page 2 of 8

FAA

Airports

ENGINEERING BRIEF #106

Guidance for the Implementation of Changes in Industry 

Cement Standard Specifications

I Purpose.

This Engineering Brief (EB) specifies design guidance for the selection of cement in 

pavement specifications in Advisory Circular (AC) 150/5370-10H, Standard 

Specifications for Construction of Airports.

II Background.

The Federal Aviation Administration (FAA) has identified a need for guidance for 

specifying which cement to use with pavement specifications. The use of blended 

cements as specified in ASTM International (ASTM) C595 / American Association of 

State Highway and Transportation Officials (AASHTO) M240 is becoming more 

common due to the reduced carbon footprint of blended cements as compared to 

traditional portland cements. ASTM C150 / AASHTO M80 no longer includes the option 

for low-alkali cement. This EB addresses the cements appropriate for use on airport 

pavement construction and how and when it is necessary to report the alkali content of 

cement.

III Application.

This EB is intended as interim guidance for the specification of cement for use in 

subgrade, subbase, base, and pavements.

IV Questions.

Contact the FAA’s Harold Honey at harold.honey@faa.gov, Jeff Crislip at 

jeffrey.d.crislip@faa.gov, Harold Muniz at harold.muniz-ruiz@faa.gov, or the current 

designated pavement engineers for any questions about this EB.

V Effective Date.

This EB is effective after signature by the Manager of the FAA Airports Engineering 

Division, AAS-100.

VI Applicable Documents.

AC 150/5370-10, Standard Specifications for Construction of Airports.
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Table of Contents

1.0 Introduction....................................................................................................................... 4

1.1. EB Guideline Justification. ..................................................................................... 4

1.2. Explanation of Terms.............................................................................................. 4

1.3. State/Local Role...................................................................................................... 4

2.0 Sustainable Cements......................................................................................................... 4

2.1. CO2 Emissions......................................................................................................... 4

2.2. When to Specify Blended Cements. ....................................................................... 4

2.3. When to Specify Standard Portland Cements......................................................... 5

3.0 Alkalies in Cement. ........................................................................................................... 5

3.1. What are Alkalies in Cement? ................................................................................ 5

3.2. Why the Concern with the Alkali Content of Cement? .......................................... 5

3.3. Alkali Content......................................................................................................... 5

3.4. Equivalent Alkali “Na2Oeq”................................................................................... 5

3.5. When to Limit Alkali Loading of Concrete Mixture .............................................. 6

3.6. How to Calculate Alkali Loading of Concrete Mixture.......................................... 6

4.0 Modifications to AC 150/5370-10H. ................................................................................ 6

4.1. P-153 Controlled Low-Strength Material (CLSM)................................................. 6

4.2. P-207 In-place, Full-Depth Reclamation (FDR) Recycled Asphalt Aggregate Base 

Course. .................................................................................................................... 6

4.3. P-220 Cement Treated Soil Base Course................................................................ 6

4.4. P-307 Cement Treated Permeable Base Course (CTPB)........................................ 7

4.5. P-501 Cement Concrete Pavement. ........................................................................ 7

4.6. P-610 Concrete for Miscellaneous Structures......................................................... 7

Acronym List................................................................................................................................. 8
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EB No. #106 FAA Airport Engineering Division Page 4 of 8

1.0 Introduction.

1.1. EB Guideline Justification.

Many cement producers have transitioned from the production of Types I and II plain 

cements, as specified in ASTM C150, to producing blended hydraulic cements such as

portland-limestone cement (IL) and other blended cements, as specified in ASTM C595. 

In addition, ASTM C150 eliminated the optional requirement of “low alkali” cements, 

and ASTM C595 has added a special property designation, HE, for high-early strength.

This EB addresses what cements are appropriate for use on airport pavement construction 

and how and when it is necessary to report the alkali content of cement. Note: This EB 

does not change the need to perform aggregate reactivity testing following ASTM C1260 

and aggregate mitigation testing following ASTM C1567 as specified in AC 150/5370-

10.

1.2. Explanation of Terms.

Terms used in this EB:

1. Alkali Content, Na2Oeq: Value in percent, determined by reporting the sodium and 

potassium oxides determined using the procedure in ASTM C114 for determination 

of sodium and potassium oxides in hydraulic cements. Report the equivalent alkali 

content using the following formula: Na2Oeq = % Na2O + 0.658  % K2O.

2. Alkali Loading: Amount of alkalies contributed by the cement in a concrete mixture, 

expressed in lb/yd3or kg/m3, calculated by multiplying the portland cement fraction 

of the concrete in lb/yd3or kg/m3, by the alkali content of the portland cement or the 

portland cement portion of a blended cement divided by 100.

1.3. State/Local Role.

State regulators, Departments of Transportation (DoTs), and local communities can use

the guidance and best practices outlined in this EB.

2.0 Sustainable Cements.

2.1. CO2 Emissions.

The use of blended cements has environmental and performance-related benefits. 

Blended cements, as specified in ASTM C595, contribute to sustainable construction by 

conserving natural resources and lowering energy consumption during manufacturing

resulting in reduced CO2 emissions. Generally, blended cements are acceptable to use in 

place of plain cements, as specified in ASTM C150, on a 1:1 replacement. Blended 

cements are often more economical, increase strength and durability, and influence other 

properties such as water demand or reactivity of aggregates.

2.2. When to Specify Blended Cements.

It is acceptable to use blended cements with P-153, P-207, P-220, P-307, P-501, or P-610. 

The FAA encourages project engineers to specify all appropriate cements available in the 

project area. The engineer should verify the availability of cements in the project area; 

not all cements are available in all regions.
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EB No. #106 FAA Airport Engineering Division Page 5 of 8

2.3. When to Specify Standard Portland Cements.

If blended cements are not available in the area, specify ASTM C150 Type I, II, or V

cements. 

3.0 Alkalies in Cement.

3.1. What are Alkalies in Cement?

Alkalies in cement and concrete refer to the amount of alkali metal elements (lithium, 

sodium, potassium, rubidium, cesium, francium) present in the cement or concrete in 

readily soluble compounds. Sodium (Na) and potassium (K) ions supply most of the 

alkali in concrete. Alkalies are inherently present in some of the raw materials used to 

produce cement. Alkalies cannot be eliminated from cement and the content can only be 

controlled to a limited degree in the manufacturing process; there is not currently a way 

to predetermine a target or desired alkali content. The alkali content of cement is 

relatively consistent for individual plants.

3.2. Why the Concern with the Alkali Content of Cement?

The alkalies, or the hydroxides thereof, contribute greatly to the pH or alkalinity of the 

cement paste. The higher the content of alkalies, the higher the pH of the pore water 

within the cement paste. Certain aggregate types have amorphous (glassy) and/or poorly 

crystalized forms of silica. In highly alkaline environments, these forms of silica can 

become unstable and susceptible to reacting with the alkalies present in the pore water 

resulting in what is known as alkali-silica reaction (ASR). This reaction forms alkalisilica gel which can swell causing deleterious expansion within the aggregate particle, the 

cement paste, or both. This expansion can lead to cracking and subsequent degradation of 

the concrete.

3.3. Alkali Content.

For many years, based upon early research, the belief was that if the alkali content of the 

cement was below a certain level, that deleterious ASR reactions could be minimized. 

This was the basis for the adoption of the maximum alkali limit of “low alkali” cement as 

Na2Oeq < 0.6%.

However, a limit on the percent of equivalent alkalies in the cement alone did not address 

the total alkali loading of the concrete. The alkali loading of the concrete takes into 

consideration the cement content of the concrete and the alkali content of the cement.

ASTM C150 no longer includes an option for low-alkali cement, but rather requires the 

cement manufacturer to report the equivalent alkali content of the cement on the mill test 

report. ASTM C595 also requires reporting of the equivalent alkali content of the 

portland cement component at the request of the purchaser.

3.4. Equivalent Alkali “Na2Oeq”.

Sodium and potassium are the predominant alkalies present in cement. However, since 

sodium and potassium have different molecular weights, adjustments are required so that 

the reported weights are based upon an equal footing rather than just providing the sum 

of sodium and potassium. This result is known as the “equivalent alkali” content and 

often referred to as Na2Oeq. Na2Oeq is the sum of: Na2O + 0.658 K2O. (Note: The 0.658 

factor is the ratio of the molecular weights of sodium and potassium.) On a mill test, the 
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EB No. #106 FAA Airport Engineering Division Page 6 of 8

“alkalies” are reported as “Na2Oeq”, or “equivalent alkali”, or “total alkali”, as tested in 

accordance with ASTM C114.

3.5. When to Limit Alkali Loading of Concrete Mixture

When either the fine or coarse aggregate to be used in P-501, Cement Concrete 

Pavement, or P-610, Concrete for Miscellaneous Structures, is potentially reactive, as 

determined by the ASTM C1260 test and as outlined in paragraphs 4.5 and 4.6, limit the 

alkali loading of the concrete mixture to be less than or equal to 3.0 lb/yd3(1.8 kg/m3).

3.6. How to Calculate Alkali Loading of Concrete Mixture.

The alkali loading of concrete (lb/yd3) = portland cement fraction content (lb/yd3) 

equivalent alkalies % Na2Oeq  1/100. Note: In concrete that includes supplementary 

cementitious materials, only the alkali content of the portland cement fraction of the 

cementitious materials is included in the calculations of alkali loading.

For example, consider a concrete mix containing 575 lbs/yd3of ASTM C595 Type IL

(15) cement which is 85% portland cement, 15% limestone. If the equivalent alkali 

content of the portland cement component is 0.63% Na2Oeq, the alkali loading of 

concrete would be:

575 lbs/yd3  85/100  0.63/100 = 3.1 lbs/yd3. (Note: In this case the mix designer must 

reduce the cement content or use a different cement to get the alkali loading below 3.0 

lb/cy.)

For another example, consider a concrete mix containing 600 lbs/yd3of ASTM C595 

Type IP (20) cement which is 80% portland cement, 20% pozzolan. If the equivalent 

alkali content of the portland cement component is 0.59% Na2Oeq, the alkali loading of 

concrete would be: 

600 lbs/yd3  80/100  0.59/100 = 2.8 lbs/yd3.

4.0 Modifications to AC 150/5370-10H.

This section provides modifications to AC 150/5370-10H for specifying cements to be 

used for subgrade, subbase, base, cement pavement, and miscellaneous concrete. Using 

the modifications included in this EB does not require submitting a formal request for a 

modification of standards (MOS). Replace the appropriate paragraph in AC 150/5370-

10H with paragraphs 4.1 through 4.6.

4.1. P-153 Controlled Low-Strength Material (CLSM).

153-2.1a. Cement. Cement: ASTM C150, Types I, II, or V; ASTM C595, Types IS, IP, 

IL, or IT.

4.2. P-207 In-place, Full-Depth Reclamation (FDR) Recycled Asphalt Aggregate Base 

Course.

207-2.2b. Chemical Stabilization. Cement: ASTM C150, Types I, II, or V; ASTM C595, 

Types IS, IP, IL, or IT.

4.3. P-220 Cement Treated Soil Base Course.

220-2.1 Cement. Cement: ASTM C150, Types I, II, or V; ASTM C595, Types IS, IP, IL, 

or IT.
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4.4. P-307 Cement Treated Permeable Base Course (CTPB).

307-2.3. Cement. Cement: ASTM C150, Types I, II, or V; ASTM C595, Types IS, IP, IL, 

or IT.

4.5. P-501 Cement Concrete Pavement.

501-2.1 a. (1) Test coarse aggregate and fine aggregate separately, in accordance with 

ASTM C1260; however, extend the length of the test to 28 days (30 days from casting). 

Complete the tests within six months of the date of the concrete submittal. If expansion of 

either the coarse or fine aggregate exceeds 0.10% at 28 days, limit the alkali loading of 

the concrete to be less than or equal to 3.0 lb per cubic yard (1.8 kg per cubic meter),

calculated in accordance with EB 106.

Note: Remaining parts of 501-2.1a remain as in AC 150/5370-10H.

501-2.2 Cement. Cement: [ASTM C150, Types I, II, or V; ASTM C595, Types IS, IP, IL, 

or IT; ASTM C1157 Types GU, HS, MS, MH, or LH]

************************************************************************************

The engineer should retain all cements appropriate for use on the project. 

Note: ASTM C1157 cements are typically only used for repair projects.

Other cements may be specified with the concurrence of the FAA.

************************************************************************************

501-3.4 Concrete Mix Submittal. Add the following information to the Concrete Mix 

submittal requirements list:

 Alkali loading contributed by the cement per cubic yard, calculated in 

accordance with EB 106.

4.6. P-610 Concrete for Miscellaneous Structures.

Add the following to the end of the first paragraph in 610-2.1a:

610-2.1a If expansion of either the coarse or fine aggregate exceeds 0.08% at 14 days,

limit the alkali of the concrete to be less than or equal to 3.0 lb per cubic yard (1.8 kg per 

cubic meter), calculated in accordance with EB 106.

610-2.4. Cement. Cement: [ASTM C150, Types I, II, or V; ASTM C595, Types IS, IP, 

IL, or IT; ASTM C1157 Types GU, HS, MS, MH, or LH.]

************************************************************************************

The engineer should retain all cements appropriate for use on the project. 

Note ASTM C1157 cements are typically only used for repair projects. Other 

cements may be specified with the concurrence of the FAA.

************************************************************************************
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EB No. #106 FAA Airport Engineering Division Page 8 of 8

Acronym List

AASHTO American Association of State Highway and Transportation 

Officials

AC Advisory Circular

ASR Alkali-Silica Reaction

ASTM ASTM International

CLSM Controlled Low-Strength Material

CO2 Carbon dioxide

CTPB Cement Treated Permeable Base Course

DoT Departments of Transportation

EB Engineering Brief

FAA Federal Aviation Administration

FDR Full-Depth Reclamation 

GU General Use

HE High-early

HS High Sulfate Resistance 

IL Portland-limestone cement

IP Portland-pozzolan cement

IS Portland blast-furnace slag cement

IT Ternary blended cement

K Potassium 

LH Low Heat of Hydration 

MH Moderate Heat of Hydration

MOS Modification of Standards

MS Moderate Sulfate Resistance 

Na Sodium