ADDENDUM TO MNL 116-21/MNL 117-13 - ASTM A1081/A1081M Testing for Strand Bond

Add the following paragraph to the Standard section in both MNL 116-21 and MNL 117-13:

Precast plants performing prestressing shall have evidence that the strand being used has been tested in accordance with ASTM A1081/A1081M, Standard Test Method for Evaluating Bond of Seven-Wire Steel Prestressing Strand. This requirement is applicable to 0.500 and 0.600-inch [12.7 and 15.24 mm] diameter strand. Test results are required for both sizes if both sizes are in use at the plant. The test results shall be updated at least annually, shall correlate to the manufacturing facility where the strand in use was produced, and shall indicate the strand size that was tested.

Add the following paragraph to the Commentary section in both MNL 116-21 and MNL 117-13:

The test results are typically provided by the strand manufacturer.

Approved 05/16/2022

MNL 117-13 Addendum – Batch Tolerances for Liquid Pigments

The corresponding paragraphs in the Standard portion of Section 4.3.1 of MNL 117-13 are revised as shown below. This change aligns MNL 117-13 with section 4.3.1 of MNL 116-21.

For cumulative batching equipment without a tare-compensated control, the following tolerances shall apply to the required cumulative scale reading:

Cementitious materials or aggregates: ± 1% of the required cumulative weight of material being weighed, or ± 0.3% of scale capacity, whichever is greater.

Solid Admixtures and Liquid Pigments: ± 3% of the required cumulative weight of material being weighed, or ± 0.3% of scale capacity, or ± the minimum dosage rate for one 94 lb (43 kg) bag of cement, whichever is greatest.

Approved 08-26-2022

MNL 116-21 Addendum – Thermal Corrections during Stressing

Remove the existing Standard and associated Commentary for Sections 5.3.10.5 and 5.3.11.5 and replace with the following:

5.3.10 Elongation Calculation and Corrections

5. Thermal effects. For abutment anchorage setups where strands are anchored to abutments that are independent from the form/mold, thermal adjustments are required if the temperature of the strand at the time of tensioning differs by more than 25°F (15°C) from the estimated fresh concrete temperature at the time of casting. Consideration shall be given to partial bed length usage and adjustments made when the net effect on the length of bed used exceeds the allowable force in the strand. The thermal coefficient of expansion of steel shall be taken as 6.5 × 10^-6/°F (12 × 10^-6/°C).

C5.3.10 Elongation Calculation and Corrections

5. Thermal effects. This item is important for abutment beds as the abutments are not affected by the temperature rise of the strand from the temperature at the time of tensioning on a cold morning to the concrete temperature at the time of placement in the forms/molds at midday or in the afternoon. The actions would be reversed for strand tensioned at elevated temperatures with cooler concrete cast around it.

Because tensioned strands are held at a fixed length, variation between ambient temperature at the time of tensioning and concrete temperature at the time of placing results in changes of stress. Lowering of strand temperature increases force, while a temperature rise results in force loss. For strands tensioned to approximately 70% to 75% of the strand ultimate tensile strength, a temperature variation in the strand of 10°F (5°C) will result in a variation of 1%. Allowance should be made in the tensioning by understressing or overstressing at the rate of 1% for 10°F (5°C) of anticipated temperature variation, depending respectively on whether a reduction or rise of temperature is anticipated. When calculating adjustments using partial bed length usage setups, the length of the strand affected by the temperature differential should be considered.

Most self-stressing beds are not affected by this phenomenon because the bed itself undergoes a similar change. As the strand is warmed and expands, the bed does as well. Because the strand is anchored to the bed, the force in the strand is relative to the bed length. As the strand is expanding and trying to relax, the bed is expanding and holding the strand at its desired value. There are some self-stressing beds that are independent of the forms/molds.  For these setups, the self-stressing bed and strand undergo similar changes as the ambient temperature changes between the time when the strands were tensioned and when concrete is placed.  However, when the concrete is placed in the form/mold, the temperature of the concrete will affect the strand but not the self-stressing bed that is independent of the form/mold.

Sample tensioning calculations with elongation corrections due to thermal effects are shown in Appendix F.

5.3.11 Force or Gauge Corrections

5. Thermal effects. For abutment anchorage setups where strands are anchored to abutments that are independent from the form/mold, thermal adjustments are required if the temperature of the strand at the time of tensioning differs by more than 25°F (15°C) from the estimated fresh concrete temperature at the time of casting. Consideration shall be given to partial bed length usage and adjustments made when the net effect on the length of bed used exceeds the allowable. The thermal coefficient of expansion of steel shall be taken as 6.5 × 10^-6/°F (12 × 10^-6/°C).

C5.3.11 Force or Gauge Corrections

5. Thermal effects. This item is important for abutment beds as the abutments are not affected by the temperature rise of the strand from the temperature at the time of tensioning on a cold morning to the concrete temperature at the time of placement in the forms/molds at midday or in the afternoon. The actions would be reversed for strand tensioned at elevated temperatures with cooler concrete cast around it.

Because tensioned strands are held at a fixed length, variation between ambient temperature at the time of tensioning and concrete temperature at the time of placing results in changes of stress. Lowering of strand temperature increases force, while a temperature rise results in force loss. For strands tensioned to approximately 70% to 75% of the strand ultimate tensile strength, a temperature variation in the strand of 10°F (5°C) will result in a variation of 1%. Allowance should be made in the tensioning by understressing or overstressing at the rate of 1% for each 10°F (5°C) of anticipated temperature variation, depending respectively on whether a reduction or rise of temperature is anticipated. When calculating adjustments using partial bed length usage setups, the length of the strand affected by the temperature differential should be considered.

Most self-stressing beds are not affected by this phenomenon because the bed itself undergoes a similar change. As the strand is warmed and expands, the bed does as well. Because the strand is anchored to the bed, the force in the strand is relative to the bed length. As the strand is expanding and trying to relax, the bed is expanding and holding the strand at its desired value. There are some self-stressing beds that are independent of the forms/molds.  For these setups, the self-stressing bed and strand undergo similar changes as the ambient temperature changes between the time when the strands were tensioned and when concrete is placed.  However, when the concrete is placed in the form/mold, the temperature of the concrete will affect the strand but not the self-stressing bed that is independent of the form/mold.

Sample tensioning calculations with force corrections due to thermal effects are shown in Appendix F.

Approved 08-31-2023

ADDENDUM TO MNL 116-21 – Fine Aggregate Gradation Limits

MNL 116-21 Addendum

Replace the existing third paragraph in Commentary section C3.1.4 with the following paragraph. The remaining portions of this section remain unchanged.

C3.1.4 Aggregates

For the fine aggregate, the maximum variation in the material passing a no. 100 (150 μm) sieve, as established in the initial mixture proportions, should not exceed 1%, to ensure uniformity of the concrete mixture.

Approved 07-15-2024

ADDENDA TO MNL 116-21 AND MNL 117-13 – Natural Stone Bondbreaker Requirements

MNL 116-21 Addendum

Revise the first two paragraphs of the Standard in the Natural Stone portion of section A2.8.9 and add the new paragraph to the associated Commentary in AC2.8.9. The remaining portions of the two sections remain unchanged.

A2.8.9 Veneer Facing Materials

Natural stone. Cut stones that are easily stained by oils and rust shall be protected by lining the form/mold with polyethylene sheets or other nonstaining materi­als.

A complete bondbreaker between natural stone veneer and concrete shall be used. The bondbreaker shall prevent concrete from entering the spaces between pieces of veneer and thereby poten­tially inhibiting differential movements. Connection of the veneer to the concrete shall be with stainless-steel mechanical anchors that can accommodate some rel­ative movement. Preformed anchors with a 5/32 in. (4 mm) minimum diameter, fabricated from Type 302 or 304 stainless steel shall be used. Close supervision is required during the insertion and setting of the anchors. Anchors placed in epoxy shall not be disturbed while the epoxy sets.

AC2.8.9 Veneer Facing Materials

Natural stone. Material such as a 6 to 10 mil (0.15 to 0.25 mm) polyethylene sheet or a 1/8 to 1/4 in. (3 to 6 mm) polyethylene foam pad or sheet have been used successfully as bondbreakers.

MNL 117-13 Addendum

Revise the first two paragraphs of the Standard in the Natural Stone portion of section 2.8.9 and add the new paragraph to the associated Commentary in C2.8.9. The remaining portions of the two sections remain unchanged.

2.8.9 Veneer Facing Materials

Natural stone. Cut stones that are easily stained by oils and rust shall be protected by lining the form/mold with polyethylene sheets or other nonstaining materials.

A complete bondbreaker between natural stone veneer and concrete shall be used. The bondbreaker shall prevent concrete from entering the spaces between pieces of veneer and thereby potentially inhibiting differential movements. Connection of the veneer to the concrete shall be with stainless steel mechanical anchors that can accommodate some relative movement. Preformed anchors with a 5/32 in. (4 mm) minimum diameter, fabricated from Type 302 or 304 stainless steel shall be used. Close supervision is required during the insertion and setting of the anchors. Anchors placed in epoxy shall not be disturbed while the epoxy sets.

C2.8.9 Veneer Facing Materials

Natural stone. Material such as a 6 to 10 mil (0.15 to 0.25 mm) polyethylene sheet or a 1/8 to 1/4 in. (3 to 6 mm) polyethylene foam pad or sheet have been used successfully as bondbreakers.

Approved 07-15-2024

This addendum to MNL 116-21 includes sample tensioning calculations for draped strand applications using US customary units. These examples supplement the examples already contained in Appendix F on MNL 116.

Due to the length and format of the examples, they do not lend themselves well to displaying in the standard dropdown format. Please use the following link to access a PDF version of the addendum:

MNL 116-21 Addendum - Appendix F – Sample Tensioning Data Calculations for Draped Strand

Approved 10-25-2024

ADDENDUM TO MNL 116-21 – Moisture Probe Verification Requirements

MNL 116-21 Addendum

Revise the following three paragraphs of the Standard in section 6.2.3.1 and the one paragraph of the associated Commentary in section C6.2.3.1 as shown below. The remaining portions of these sections remain unchanged.

6.2.3.1 Aggregates. Any method that is used to measure aggregate free-surface moisture shall result in free-moisture values that are representative of the aggregate entering the mixer.

The moisture detection equipment (e.g., moisture meter, electric probe, or microwave energy absorption) is satisfactory for moisture determination provided it is calibrated against the results obtained using the drying method (ASTM C566). The moisture detection equipment shall be reviewed for accuracy at weekly intervals for each aggregate type during regular use and adjusted if necessary.

If continuous moisture detection equipment is not used, the free-surface moisture shall be determined at the beginning of any batching operation and at any time there is visual change in the mixture consistency or an obvious change in moisture content.

C6.2.3.1 Aggregates. It is necessary to calibrate moisture sensors for each material. Since moisture sensors do not provide a direct moisture content reading, the “calibration” function, as used herein, consists of a correlation of the moisture sensor reading to the results of an oven dried moisture content test. Moisture sensors should be checked against and calibrated to oven dried tests over the entire expected operating range of moisture contents. The total time to complete a calibration depends on the drying time; however, most calibrations can take less than three hours. Sensors are subject to wear, and if they are out of adjustment or not positioned correctly in the flow of material, they will not provide an accurate reading.

Approved 06-09-2025

The following sections of MNL 116-21 are revised to incorporate requirements and the associated commentary for stainless steel strand and for Carbon Fiber Reinforced Polymer (CFRP) tendons.

Due to the length of the addendum, it does not lend itself well to displaying in the standard dropdown format. Please use the following link to access a PDF version of the addendum:

MNL 116-21 Addendum - SS and CFRP Strand

Approved 10-17-2025

The following sections of MNL 116-21 and MNL 117-13 are revised to incorporate requirements and the associated commentary for post-installed anchors.

Due to the length of the addendum, it does not lend itself well to displaying in the standard dropdown format. Please use the following link to access a PDF version of the addendum:

MNL 116-117 Addendum - Post-installed Anchors

Approved 11-07-2025

The following sections of MNL 116-21 are revised to incorporate requirements and the associated commentary for structural ultra-high-performance concrete (UHPC).

Due to the length of the addendum, it does not lend itself well to displaying in the standard dropdown format. Please use the following link to access a PDF version of the addendum:

MNL 116-21 Addendum - Structural UHPC Requirements

Approved 11-26-2025

The following standard requirements in MNL 116-21 and MNL 117-13 have been revised.

MNL 116-21 Addendum

Modify Section 1.3.1, Personnel - General

(Add the requirement shown below to section 1.3.1.)

For plants that use SCC, at least one individual involved in the testing of fresh SCC or directing such tests shall maintain a current ACI Self-Consolidating Concrete Testing Technician certification or PCI-approved equivalent certification.

Revise Section 6.2.1, Testing - General

(Remove the two paragraphs shown below from section 6.2.1 and replace them with the alternate text that follows. The balance of this section remains unchanged.)

Individuals who perform aggregate gradation tests, fresh concrete tests, or concrete cylinder strength tests for acceptance shall meet the technician requirements of Practice C1077 or receive in-house training that includes, after a reasonable time period, an examination requiring a performance demonstration that is evaluated and documented by an independent examiner not in the employ of the plant or by a professional engineer. This documented training shall be renewed every five years.

At least one individual involved in the testing of fresh concrete or directing such tests shall maintain a current ACI Concrete Field Testing Technician – Grade 1 certification or PCI-approved equivalent certification. Individuals who perform fresh concrete testing without ACI Concrete Field Testing Technician – Grade 1 certification shall receive in-house training that includes, after a reasonable time period, an examination requiring a performance demonstration that is evaluated and documented by an independent examiner not in the employ of the plant. This documented training shall be renewed every five years.

Individuals who perform aggregate gradation tests or concrete cylinder strength tests for acceptance without ACI Aggregate Testing Technician – Level I, ACI Concrete Strength Testing Technician, or ACI Laboratory Testing Technician – Level I certification, as appropriate to their duties, shall receive in-house training that includes an examination requiring a performance demonstration of their ability to properly perform the tests before they are allowed to perform the test independently.

At least one individual involved in the testing of fresh concrete or directing such tests shall maintain a current ACI Concrete Field Testing Technician – Grade 1 certification or PCI-approved equivalent certification. For plants that use SCC, at least one individual involved in the testing of fresh SCC or directing such tests shall maintain a current ACI Self-Consolidating Concrete Testing Technician certification or PCI-approved equivalent certification. Individuals who perform fresh concrete testing for acceptance without ACI Concrete Field Testing Technician – Grade 1 certification or Self-Consolidating Concrete Testing Technician certification, as appropriate to the type of concrete being tested, shall receive in-house training that includes an examination requiring a performance demonstration of their ability to properly perform the tests before they are allowed to perform the test independently.

The performance demonstrations shall be evaluated and documented by one of the following:

1. an individual certified in accordance with ASTM C1077 in the appropriate group of testing
2. a professional engineer
3. an examiner not in the employ of the plant who is competent by reason of training, experience, or certification in the test(s) being evaluated

This documented performance demonstration shall be renewed every five years.

Documentation of the performance demonstration must include:

• Name of technician
• Date of demonstration
• Location of test
• Identification of the test or practice demonstrated
• Listing of the significant steps in the practice or test method
• Whether the demonstration was passed
• Name, signature, and qualifications of examiner

MNL 117-13 Addendum

Modify Section 1.3.1, Personnel - General

(Add the requirement shown below to section 1.3.1.)

For plants that use SCC, at least one individual involved in the testing of fresh SCC or directing such tests shall maintain a current ACI Self-Consolidating Concrete Testing Technician certification or PCI-approved equivalent certification.

Revise Section 6.2.1, Testing - General

(Remove the paragraph shown below from section 6.2.1 and replace it with the alternate text that follows. The balance of this section remains unchanged.)

At least one individual involved in the testing of fresh concrete or directing such tests shall maintain a current ACI Field Testing Technician, Grade 1, certification or approved equivalent certification.

Individuals who perform aggregate gradation tests or concrete cylinder strength tests for acceptance without ACI Aggregate Testing Technician – Level I, ACI Concrete Strength Testing Technician, or ACI Laboratory Testing Technician – Level I certification, as appropriate to their duties, shall receive in-house training that includes an examination requiring a performance demonstration of their ability to properly perform the tests before they are allowed to perform the test independently.

At least one individual involved in the testing of fresh concrete or directing such tests shall maintain a current ACI Concrete Field Testing Technician – Grade 1 certification or PCI-approved equivalent certification. For plants that use SCC, at least one individual involved in the testing of fresh SCC or directing such tests shall maintain a current ACI Self-Consolidating Concrete Testing Technician certification or PCI-approved equivalent certification. Individuals who perform fresh concrete testing for acceptance without ACI Concrete Field Testing Technician – Grade 1 certification or Self-Consolidating Concrete Testing Technician certification, as appropriate to the concrete being tested, shall receive in-house training that includes an examination requiring a performance demonstration of their ability to properly perform the tests before they are allowed to perform the test independently.

The performance demonstrations shall be evaluated and documented by one of the following:

1. an individual certified in accordance with ASTM C1077 in the appropriate group of testing
2. a professional engineer
3. an examiner not in the employ of the plant who is competent by reason of training, experience, or certification in the test(s) being evaluated

This documented performance demonstration shall be renewed every five years.

Documentation of the performance demonstration must include:

• Name of technician
• Date of demonstration
• Location of test
• Identification of the test or practice demonstrated
• Listing of the significant steps in the practice or test method
• Whether the demonstration was passed
• Name, signature, and qualifications of examiner

Approved: 01/28/2026
Effective: 01/01/2027