Amend 002 SOW Corrosion and Durability_QandA.pdf

STATEMENT OF WORK

Corrosion and Concrete Durability Expertise and Testing Services for Champlain Tower South Investigation

Table of Contents

1.0 Background

2.0 Scope and Objectives

3.0 Base Tasks

3.1 Task 1: Safety Plan

3.2 Task 2: Expert Corrosion and Concrete Durability Consultation Services

3.3 Task 3: Corrosion Potential and Corrosion Rate Mapping

3.4 Task 4: Concrete Transport Property Measurements

3.4.1 Task 4.1: Develop and Experimental Plan

3.4.2 Task 4.2: ASTM C1202-19 Measurements on Type A Cores

3.4.3 Task 4.3: Water Absorption and Drying Rate Measurement on Type A Cores

3.4.4 Task 4.4: Chlorine (Cl) Diffusion Coefficient and Carbonation Rate Estimation on Type B or Type C Cores 76

3.5 Task 5: Accelerated Corrosion Testing on Mock-ups

3.5.1 Task 5.1: Develop Plan for Accelerated Corrosion Testing Procedure

3.5.2 Task 5.2: Construct Test Specimens and Implement the Natural and Accelerated Corrosion Procedures

3.5.3 Task 5.3: Convey Experience to NIST and its Consultants Conducting Structural Loading Tests

3.5.4 Task 5.4: Establishing Degree of Corrosion by Loss of Mass

3.6 Task 6: Service Life Modeling

3.7 Task 7: Data Collection, Reporting, and Communication

4.0 Optional Tasks

4.1 Optional Task 8: Extend Corrosion Potential and Corrosion Rate Mapping by 15 Specimens1615

4.2 Optional Task 9: Second Round of Cores for Concrete Transport Properties

5.0 Deliverables

6.0 Performance Requirements

7.0 Government-Furnished Property, Material, Equipment, or Information (GFP, GFM, GFE, or GFI)

8.0 Risk Levels

9.0 Travel

10.0 Key Personnel Requirements

11.0 Required Laboratory Certifications

12.0 Data Reporting and Sharing

13.0 Preservation of Physical Evidence

14.0 Place of Performance

15.0 Period of Performance

16.0 Appendix A: Safety Requirements for Working in PEF

1.0 Background

The National Construction Safety Team Act (“Act”), Pub. L. 107-231, codified at 15 U.S.C. 7301 et seq., was enacted to provide for the establishment of investigative teams (“Teams”) to assess building performance and emergency response and evacuation procedures in the wake of any building failure that has resulted in substantial loss of life or that posed the significant potential of substantial loss of life.

The purpose of investigations by Teams is to improve the safety and structural integrity of buildings in the United States. As stated in the statute, a Team shall (1) establish the likely technical cause or causes of the building failure; (2) evaluate the technical aspects of evacuation and emergency response procedures; (3) recommend, as necessary, specific improvements to building standards, codes, and practices based on the findings made pursuant to (1) and (2); and (4) recommend any research and other appropriate actions needed to improve the structural safety of buildings and improve evacuation and emergency response procedures, based on the findings of the investigation.

On June 24th, 2021, the Champlain Tower South Condominium suffered a partial collapse. NIST sent a preliminary reconnaissance team to collect information and data related to the collapse. Based on the recommendations of the preliminary reconnaissance team and evaluation of the criteria listed in the regulations implementing the Act, specifically in 15 CFR § 270.102, on June 30, 2021, the Director of the National Institute of Standards and Technology (NIST), United States Department of Commerce, established a Team to study the collapse of the Champlain Towers South Condominium in Surfside, FL.

The Team may include members who are Federal employees and members who are not Federal employees. Team members who are Federal employees are governed by the Federal conflict of interest laws. Team members who are not Federal employees will be Federal government contractors.

2.0 Scope and Objectives

The Team requires expertise in steel corrosion of reinforced concrete elements and concrete transport properties to assist with establishing the technical cause or causes of the Champlain Towers South Collapse. The Contractor shall provide consultation services to NCST investigators regarding the technical mechanisms of steel corrosion of reinforced concrete elements, conduct tests on the transport properties of concrete extracted from evidentiary building debris, collect necessary data and information to conduct service life predictions of structural elements, and provide the NCST investigation with written progress reports.

The objective of this requirement is to obtain expert consulting services related to reinforced concrete corrosion as well as contractor services to 1) conduct corrosion potential and corrosion rate measurements on 30 reinforced concrete specimens, 2) measure the transport properties of 100 concrete cores extracted from specimens, 3) conduct accelerated corrosion testing on reinforced concrete slabs,

4) communicate the results to the Structural Testing Contractor and to the Bureau of Reclamation (under an Inter-Agency Agreement with NIST), and 5) conduct service life prediction modeling of specimens.

The Contractor shall provide technical input to the NCST investigation into the collapse of Champlain Towers South regarding corrosion of steel in reinforced concrete, concrete durability, concrete transport property measurements, simulations of reinforced concrete durability, estimates of service life, and shall conduct an accelerated corrosion test on reinforced concrete slab specimens.

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The Contractor shall provide all services detailed in this Statement of Work, including expert consultation services in corrosion of embedded steel in concrete, concrete durability, and reinforced concrete service life modeling; conducting transport property measurements of concrete materials; conducting corrosion rate and corrosion potential measurements; conducting accelerated corrosion tests; and conducting service life modeling of reinforced concrete elements.

The Contractor shall perform onsite measurements of the corrosion rate and corrosion potential of specimens stored in the Primary Evidence Facility (PEF) located in Miami, FL. The activities of Tasks 4.1, 4.3, 4.4, and 4.5 may be performed at the Contractor's facility. Remote work may include analysis, presentations, and technical reports documenting the investigation being performed pertaining to the partial collapse.

Onsite Availability The Contractor shall be available to be onsite to perform the activities of Task 2 prior to and during the core extraction process. NIST expects core extraction to occur between the date of award and June 30, 2023.

Equipment and Personnel The contractor shall provide all equipment and personnel required to complete the tasks identified in this Statement of Work except for what is specified in the Government-Furnished Property section of this document.

This is a firm-fixed price (FFP) contract requirement.

3.0 Base Tasks

3.1 Task 1: Safety Plan

The contractor shall provide to NIST and the NCST investigation a written plan describing the hazards and mitigation methods associated with the required NDT and executing the NDT in the PEF. The safety plan shall include the personal protective equipment (PPE) required for each NDT which shall be supplied by the Contractor. The safety plan shall comply with all NIST safety requirements for working inside the PEF (see Appendix A) and shall be submitted to NIST prior to the start of any NDT activities.

3.2 Task 2: Expert Corrosion and Concrete Durability Consultation Services The contractor shall provide expert consultation services regarding the corrosion of steel reinforcing bars in concrete as needed and advise on accelerated corrosion tests of reinforced concrete specimens in support of activities in Tasks 2 through 6 we well as optional tasks 7 and 8, if exercised.

3.3 Task 3: Corrosion Potential and Corrosion Rate Mapping

The Contractor shall conduct corrosion potential and corrosion rate mapping of 30 reinforced concrete specimens identified by NIST, comprised of slabs, columns, beams, and walls at the PEF in Miami, FL, according to ASTM C876-15. The Contractor shall work with NIST and the NCST investigation to identify samples to measure during this task. The Contractor shall identify regions of the 30 specimens that may contain corroded steel, recommend regions from which to extract concrete cores. Technical reports and data collected from this task shall be made available as described in Task 6. The Contractor shall furnish all equipment and personnel necessary to obtain corrosion potential and corrosion rate measurements and is responsible for maintaining calibration records.

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3.4 Task 4: Concrete Transport Property Measurements

The Contractor shall measure the transport properties on pucks obtained from 4 in. diameter concrete cores designated Type A or from concrete cores with diameters ranging from 2 in. to 4

in. designated Type B, or Type C, supplied by NIST, which are extracted from evidentiary building debris.

General information and requirements regarding the core types are included below, and further Task 4 subtask requirements follow.

Type A Cores

Type A cores are to be used to assess the water absorption, drying rate, resistance to chloride penetration, and physical properties such as bulk density and air void percentage. The expected lengths of the cores is (9 1) in. or (16 1.5) in. The Contractor shall receive Type A either sectioned into pucks by NIST or as a complete core. If received as a complete core from NIST, the contractor shall section the core into pucks 2 inches long, as schematically shown in Figure

4.1. The following tests shall be performed on pucks from Type A cores per the requirements of Sub Tasks 4.2 and 4.3:

The contractor shall test fifteen 16 in. long cores, and twenty-five 9 in. long cores resulting in the number of pucks for the following tests:

Pucks 1, 2, 6, 7, and 8 (125 total) shall be tested per the following test(s): ASTM C1585- 20, ASTM C1792-14, ASTM C642-21, ASTM C1356-07(2020), and an agreed-upon bulk resistivity test.

Pucks 3, 4, and 5 (95 total) shall be tested per the following test(s): ASTM C1202-19.

NIST requires the Contractor to provide services for 125 ASTM C1585-20, ASTM C1792-14, ASTM C642-21, ASTM C1356-07(2020) tests, and an agreed-upon bulk resistivity test as well as 95 tests per ASTM C1202-19.

Type B and C Cores

Type B and C cores are to be used to assess chloride diffusion and carbonation rates per the requirements of Sub Task 4.4. Type C cores do not contain a reinforcing bar section, while Type B cores are extracted from an area of reinforcing bar corrosion and will contain a reinforcing bar.

The Contractor shall conduct chloride profile measurements according to ASTM C1152-20 and estimate apparent diffusivity per ASTM C1556-11a(2016) on Type B and Type C cores. NIST requires the Contractor to provide chloride diffusion and carbonation rate testing services for 145 cores (inclusive of both Type B and Type C cores). NIST expects approximately 50% of the cores will be Type B with the remaining being Type C.

NIST will coordinate the shipping of all extracted cores to the Contractor's facility. The Contractor shall be responsible for preparing the cores for testing per the requirements of the specified test and returning the cores to NIST after testing is complete. The contractor shall pay all return shipping cost to NIST’s Gaithersburg campus, located at 100 Bureau Dr. Gaithersburg, MD 20899-8615.

(a) Type A Core (b) Type A Core – 9 in length

(c) Type B Core (d) Type C Core

Figure 4.1: Schematic Diagrams of samples to be obtained from cores extracted from evidentiary building debris. Note: Petrography per ASTM C856 is not required for pucks.

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Summary of Expected Number of Cores

The expected number of cores and the total number of pucks are summarized in Table 4.1

Table 4.1: Summary of the expected number of Type A cores and the total number of pucks to be tested.

For ASTM C1585-20, ASTM C1792-14, ASTM C642-21, ASTM C1356-07(2020) tests, and an agreed-upon bulk resistivity test:

Expected Number of Cores

Pucks/core Total Pucks

16 in Cores 15 5 75 9 in Cores 25 2 50

Total 125 For ASTM C1202-19 tests:

Expected Number of

Cores Pucks/core Total Pucks

16 in Cores 15 3 45 9 in Cores 25 2 50

Total 95

3.4.1 Task 4.1: Develop and Experimental Plan

The Contractor shall, in consultation with NIST, develop an experimental plan to measure the transport and durability properties of concrete cores extracted from evidentiary building debris.

The Contractor shall coordinate testing requirements and coordinate data sharing with NIST and NCST personnel to develop a written comprehensive experimental plan. The Contractor’s written experimental plan shall describe all test methods and the equipment to be used and shall include safety provisions for all Contractor personnel. The written test plan shall include details on labeling and storing of specimens and data, handling procedures, and procedures for storing materials after testing.

The draft experimental plan shall be submitted to NIST for review. The NIST COR will provide feedback to the Contractor regarding modifications to the plan that may be necessary to serve investigative purposes and the Contractor shall revise the plan accordingly for final review.

3.4.2 Task 4.2: ASTM C1202-19 Measurements on Type A Cores

The Contractor shall measure the resistance to chlorine penetration of 95 pucks extracted from evidentiary building debris per ASTM C1202-19.

3.4.3 Task 4.3: Water Absorption and Drying Rate Measurement on Type A Cores The Contractor shall measure the water absorption and drying rate of 125 pucks extracted from evidentiary building debris.

The Contractor shall collaborate with NIST to develop a procedure for conducting water absorption and drying rate tests per ASTM C1585-20 and ASTM C1792-14, respectively. The procedure shall include additional steps to document the condition of the pucks, conduct point counting according to ASTM C1356-07(2020), and determine the density and voids content for Champlain Tower South Investigation according to ASTM C642-21. The Contractor shall report to NIST and the NCST investigation team an experimental procedure for conducting these tests to satisfy the requirements of the investigation. NIST and the NCST investigation team will work with the Contractor to modify test procedures as appropriate for the investigation.

Once a test procedure is approved by NIST, the procedure shall be conducted on 125 pucks. The procedure shall include the following activities for each puck:

1. Visually examine and photograph the puck.

2. Make physical measurements of specimen diameter and thickness so that volume and density can be estimated.

3. Conduct point counting on both cut surfaces to estimate air content and aggregate volume fraction according to ASTM C1356-07(2020).

4. Collect mosaic images of the entire cut surface using light microscopy.

5. Determine the puck mass.

6. Saturate the puck in a solution specified by NIST, until the daily mass gain is less than

0.5%.

a. Possible saturation fluids to be specified by NIST: distilled water, synthetic pore solution, or synthetic Miami groundwater.

7. Determine the mass of the saturated puck.

8. Measure the bulk resistivity of the saturated puck.

9. Conduct a one-dimensional drying rate test according to ASTM C1792-14.

10. Conduct absorptivity test according to ASTM C1585-20.

11. Conduct ASTM C642-21.

The point counting in step 3 shall be conducted per ASTM C1356. This means the grid, counts, and uncertainty estimation shall be conducted per this standard. Per the ASTM standards, adjacent points shall not sample the same feature. The features of interest in the point counting are aggregates, voids, cement, and hardened cement paste. The specimen shall be imaged per the procedures in ASTM C457 at spatial resolution of 2 m/pixel to 4 m /pixel.

3.4.4 Task 4.4: Chlorine (Cl) Diffusion Coefficient and Carbonation Rate Estimation on Type B or Type C Cores

The Contractor shall measure the Cl profiles, calculate estimated diffusion coefficients and estimate carbonation rates for up to 14 cores provided by NIST. NIST expects approximately 50% of the cores will be Type B with the remaining will be Type C. The choice of Type B or Type C core will be made by NIST and the NCST investigation team. The Type B or C core shall be split by the Contractor along the length of the core in the split tension configuration (Brazilian test). If splitting is not possible due to the condition of the core, permission to saw cut the specimen shall first be obtained from the NIST COR to cut such cylinders.

3.4.4.1 Task 4.4.1: Acid Soluble Chloride Profile - ASTM C1152-20

The acid-soluble chlorides of each cores shall be determined by the Contractor according to ASTM C1152-20 with each profile containing a minimum of 8 depths.

3.4.4.2 Task 4.4.2: Apparent Chloride Diffusion Coefficient - ASTM C1556-11a(2016)

The apparent Cl diffusion coefficient of each core shall be determined by the Contractor using the procedures outlined in ASTM C1556-11a(2016).

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3.4.4.3 Task 4.4.3: Carbonation rates

Carbonation depths shall be determined by the Contractor for each core using a phenolphthalein indicator on Type B or C cores; from this depth measurement, a rate of carbonation shall be inferred by the Contractor.

3.5 Task 5: Accelerated Corrosion Testing on Mock-ups

The Contractor shall develop an accelerated corrosion testing procedure, conduct that procedure on four full-scale mock-ups of portions of the CTS plaza slab, and report to NIST the resultant findings per the Sub Tasks described below.

3.5.1 Task 5.1: Develop Plan for Accelerated Corrosion Testing Procedure The Contractor shall develop a plan for an accelerated testing procedure to be carried out at the Contractor’s laboratory. The plan shall be developed for four identical test specimens having the configuration and dimensions shown in Figure 54.12 below. The test plan shall include the following:

Specimen 1: Natural corrosion with saltwater pond, with reinforcing bar corrosion and concrete cracking monitored using appropriate Non-destructive Testing (NDT) supplied and conducted by the Contractor.

Specimens 2-4: Corrosion induced by the impressed current. For these test specimens, the Contractor shall consider two different approaches for accelerated corrosion: (1) target degrees of corrosion (defined as the ratio of the mass loss due to corrosion to the mass of the original, uncorroded bar) ranging between 1 % and 10%, with the specimen being broken to examine conditions at the target times determined based on calculations considering the impressed current or other established methods and; (2) applying different currents, monitoring corrosion and cracking with NDT, and breaking open specimens at target times to compare corrosion and cracking based on the NDT and direct observation.

The Contractor shall make recommendations to NIST on the target degrees of corrosion based on (a) observations from the evidence in the PEF and (b) estimates of degrees of corrosion that will bracket concrete damage. The Contractor is encouraged to use their experience to propose alternative approaches that lead to an understanding of the relationship between the degree of corrosion and the amount and type of concrete damage. The Contractor shall advise on electrical continuity of reinforcing steel and any other arrangements to facilitate artificial aging in advance of casting specimens.

The test plan shall describe the use of the NDT procedures to be used by the Contractor to monitor corrosion and cracking. The Contractor shall develop a letter report that documents alternative approaches for accelerated corrosion, along with their advantages and disadvantages. The letter report shall be discussed with NIST and the NCST investigation team, who, together with the Contractor, shall select an accelerated corrosion procedure to be implemented in Task 5.2.

Figure 54.12: Configuration and dimensions of specimens for the accelerated corrosion testing.

3.5.2 Task 5.2: Construct Test Specimens and Implement the Natural and Accelerated Corrosion Procedures

The Contractor shall provide all labor, material, and equipment necessary to construct four test specimens having the configuration shown in Figure 54.12 with the exception that NIST will provide the concrete mixture design and the concrete aggregate, cement, and any admixtures required to make the concrete used in the test specimens and concrete test cylinders. The Contractor shall be responsible to transport the coarse and fine aggregates, cement, and any admixtures from a location in Miami, Florida to the Contractor’s testing laboratory. Reinforcement shall be ASTM A615 Grade 60 reinforcement. Concrete shall be produced to match a selected Nominal 4000-psi floor concrete. The concrete mixture will be specified by NIST prior to the time of casting.

NIST estimates that the proportions and constituents will be approximately as shown in Table

54.1 below. Before mixing the concrete, the Contractor shall contact the COR and TPOC to confirm or update the mixture proportions shown in Table 54.1. The COR will either confirm the proportions or will provide updated mixture proportions within five business days of contract award.

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Table 54.1: Target compressive strength and NIST-estimated mixture proportions for Nominal 4000-psi Floor Concrete

Target Compressive Strength

4700 psi

Component Mass Proportion 𝑙𝑏/ 𝑦𝑑

Density 𝑙𝑏/𝑓𝑡 Volume 𝑓𝑡

Water 306 62.4 4.91

Cement* 600 197 3.05

Air-Entraining Admixture

Will be identified, if any, and provided by NIST

Water Reducing Admixture

Will be identified, if any, and provided by NIST

Total Air (3 %) – – 0.81

Subtotal paste + air 906 8.77

Total Aggregate Volume

27 8.77 18.23 Typically, close to 19

SDD Coarse Aggregates**

1560 2.5 ∗ 62.4 156 10.03 @55 %

SDD Fine Aggregates***

1339 2.6 ∗ 62.4 162 8.20 @45 %

Total 𝑙𝑏/𝑦𝑑 3805

Total Volume 27

Fresh Density 141 𝑙𝑏/𝑓𝑡

*Cement shall be procured by NIST and stored at the PEF in Miami, FL. The Contractor shall be responsible for shipping the cement from the PEF to the Contractor’s location.

**Coarse aggregate shall be ASTM C33 crushed limestone obtained from designated south Florida quarries with nominal maximum aggregate size = ¾ in. To be provided by NIST.

*** Fine aggregate shall be concrete sand meeting the requirements of ASTM C33 for quality and grading. To be provided by NIST.

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The Contractor shall construct the four test specimens in the Contractor’s facilities. The date and time of casting shall be scheduled to permit on-site attendance by NIST representatives.

Specimens shall be cast in an upright position to match the direction of the casting of the plaza slab in the CTS building. The general construction procedure shall be in accordance with ACI 301 to include thorough consolidation with an immersion vibrator. The addition of water to increase workability is prohibited unless specifically approved in writing by the NIST COR, and then only when the concrete quantity and the amount of added water are known such that the resulting water to cement ratio can be accurately computed. Specimens shall be cured by keeping all exposed surfaces continuously and visibly wet-cured for 14 days and then may be removed from their wet-curing environment to prepare them for corrosion testing.

The Contractor shall cast a sufficient number of companion concrete cylinders, of 6 in. diameter by 12 in. long, to be used for monitoring the development of concrete material properties. At least three compression tests shall be conducted at each of 7 days, 14 days, 21 days, 28 days, (28 + n)/2 days, and n days, plus three split cylinder tests at 28 days and at n days, where n is the intended number of days from time of casting to time of completion of the corrosion tests on the four test specimens. Water absorption and drying rate tests shall be conducted per the specifications in Task 4.3 at n days of age. Cylinders shall be cured along with and under similar conditions as the test specimens rather than being cured in a fog room. The objective of the cylinder tests is to monitor the development of the material strengths over the duration of the test specimen corrosion tests.

The Contractor shall carry out the corrosion tests in accordance with the test plan developed in Task 5.1. Reasonable deviations from the test plan, as needed to better accomplish the goals of the test program, are permitted with the advance concurrence of the COR.

This task includes the development of a report that documents the results of the corrosion test program, including the relationship between the degree of corrosion and the degree of concrete cracking, as well as a discussion on the merits of the various methods employed. The report shall also document the results of the cylinder compression and splitting tensile tests.

3.5.3 Task 5.3: Convey Experience to NIST and its Consultants Conducting Structural Loading Tests

The primary purpose of the tests in Task 5.2 is to gain knowledge and experience in the conduct of accelerated corrosion tests on test specimens similar to those shown in Figure 54.1. For Task 5.3, the Contractor shall convey that knowledge and experience to the NIST Structural Testing Contractor (to be identified post-award) who will be carrying out structural loading tests of full-scale mock-ups of slab-column connections of the plaza slab of the CTS building. The NIST Structural Testing Contractor is expected to be located within the continental United States. NIST also plans to have additional structural testing of columns at the Bureau of Reclamation (BOR) laboratory in Denver, Colorado, including two columns that will be subjected to accelerated corrosion prior to structural testing. A secondary purpose of this task is to convey the knowledge to the BOR test program.

For information, the tests conducted by the NIST Structural Testing Contractor shall include three tests on slab-column connections with corrosion in the slab’s top reinforcing bars and column’s upper reinforcement. Two tests shall have a moderate amount of corrosion, while a third test shall have an advanced amount of corrosion (the actual degrees of corrosion will be determined at a for Champlain Tower South Investigation later date). The specimens with corroded reinforcement shall then be tested to determine the effect of corrosion on the stiffness, strength, and deformation capacity of the connections.

The Contractor shall work with NIST and its Structural Testing Contractor to convey knowledge and experience gained during Task 5.2. This work shall include:

Sharing written reports from Tasks 5.1 and 5.2 with the NIST Structural Testing Contractor.

Two video conferences with NIST and its Structural Testing Contractor to describe the written reports and to help develop procedures that can be used by the NIST Structural Testing Contractor to obtain target degrees of corrosion in the structural loading test specimens.

One trip to the laboratory facilities of the NIST Structural Testing Contractor to review procedures and laboratory test setups to be used for the corrosion tests.

Review of the corrosion test results of the NIST Structural Testing Contractor and preparation of a letter report to NIST to summarize the findings of the corrosion test results.

The tests conducted by the BOR will include two tests on columns representative of basement columns in the CTS having 14” x 18” cross sections reinforced with ten lap-spliced No. 11 longitudinal bars, one with well-consolidated concrete and one with poorly consolidated concrete.

The columns will be subjected to accelerated corrosion prior to structural testing – the degree of corrosion, to be determined at a later date, is likely to be in the range of 5 % - 10 %. The purpose of the tests is to determine how corrosion affects the strength and failure mode of axially loaded columns.

The Contractor shall work with NIST and the BOR to convey knowledge and experience gained during Task 5.2. This work shall include:

Sharing written reports from Tasks 54.1 and 54.2 with the BOR.

Two video conferences with NIST and BOR to describe the written reports and to help develop procedures that can be used by the BOR to obtain target degrees of corrosion in the structural loading test specimens.

Review of the corrosion test results of the BOR and preparation of a letter report to NIST to summarize the findings of the corrosion test results on the test columns.

3.5.4 Task 5.4: Establishing Degree of Corrosion by Loss of Mass The Contractor shall conduct measurements to establish the degree of corrosion by loss of mass of 100 reinforcing bar specimens selected and extracted by NIST from evidentiary building debris in the PEF. The 100 specimens shall be No. 4, 5, 7, 10, and 11 reinforcing bars, the exact numbers of each size shall be determined by NIST. The Contractor shall remove corrosion products from the reinforcing bar specimens per the cleaning procedures described in ASTM G1- 03(2017) e1 Standard Practice for Preparing, Cleaning, and Evaluation Corrosion Test Specimens. The following procedure shall be conducted:

1. Determine the mass of corroded reinforcing bar sample to obtain starting mass.

2. Visually examine and photograph the sample with a length scale bar.

a. Note reinforcing bar grade markings.

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b. Determine the sample amass and determine the length.

3. Remove loose corrosion products by scraping. Preserve loose corrosion products in a sealed container. Scraping shall be performed with a non-metallic bristle brush.

4. Apply cleaning procedure C.3.5 per ASTM G1-03(2017)e1.

a. Determine the mass of the sample prior to the start of the cleaning procedure.

b. Apply cleaning procedure

c. Examine the sample to determine the complete removal of corrosion product

i. Examine the sample with microscopy to ensure all corrosion product has been removed.

d. Determine sample mass after cleaning procedure.

5. Plot the mass loss after each cleaning procedure as a function of the number of applications of the cleaning procedure. Repeat the cleaning procedure until the mass loss is less than 0.1 % of the original sample mass in two consecutive cleaning procedures.

a. After the 0.1 % threshold has been reached, conduct a final examination with microscopy to ensure complete removal of corrosion products.

b. Samples shall be dried and stored in an environment with a relative humidity of less than 60 % between cleaning cycles.

The following shall be reported for each sample:

1. The initial mass of the sample, before and after mechanical removal of rust.

2. Photographs and examination notes.

3. Microscopy images captured during cleaning.

4. Sample mass after each cleaning procedure.

The total mass loss shall be determined by the Contractor by subtracting the final sample mass from a starting sample mass that shall be estimated from reinforcing bars of similar size and grade recovered from evidentiary building debris. The starting sample mass will be provided by NIST.

Note that there is mill scale on bars from the plant that is removed by the cleaning process. The mass with and without mill scale shall be noted by the Contractor.

The Contractor shall develop a report that documents the results of the degree of corrosion by loss of mass for all 50 corroded reinforcing bar specimens and for 50 non-corroded reinforcing bar specimens. The scrapings collected at the start of the cleaning process shall be returned to NIST. Rebar lengths are expected ot be between 6 in and 12 in.

3.6 Task 6: Service Life Modeling

The Contractor shall develop service life models at three field locations selected by NIST and the NCST. The Contractor shall conduct service life design simulations per the specifications outlined in the Unified Facilities Guide Specification (UFGS - 03-31-29) Marine Concrete with Service Life Modeling using either STADIUM Lab software or the fib Bulletin 34 Model Code for Service life Design.

The field locations will constitute 4 in. diameter cores of the type in Figure 4.1and will be supplied by NIST to the contractor. The contractor shall be responsible for producing all model inputs.

If using STADIUM Lab software, the required inputs are listed in Table 64.11, except where specified. The contractor shall use the concrete cores cast during the creation of the specimens for Champlain Tower South Investigation in Task 5 to determine the aging function listed in Table 64.12 below. A minimum of three concrete ages is required.

If using fib Bulletin 34 Model Code for Service Life Design, a full probabilistic approach for chloride-induced corrosion shall be implemented. All input parameters are to be documented. A justification for each input choice shall be articulated with supplemental data and cited literature.

Concrete transport properties shall be tested per NT Build 492 with raw data and calculations supplied to NIST. The contractor shall conduct NT Build 492 using concrete cores cast during the creation of the specimens in Task 5.

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Table 64.12: Inputs required by NIST for service life modeling Input Parameter ASTM Test

Method NIST Requirements

Material Properties Volume of permeable pores (porosity)

ASTM C642 Conduct per ASTM test method in sequence with other tests as detailed in Task 4.4

Diffusion Coefficient ASTM C1202 Conduct a modified version of ASTM C1202 test method in sequence with other tests as detailed in Task 4.4.

ASTM C1202 shall be conducted to comply with the requirements software STADIUM Lab. ASTM C1202 shall be conducted on saturated pucks at 20 V.

Intrinsic Permeability ASTM C1792 Conduct per ASTM test method in sequence with other tests as detailed in Task 4.4.

Moisture Isotherm ASTM C1585 Conduct per ASTM test method in sequence with other tests as detailed in Task 4.4. Moisture isotherms shall be obtained following procedures that meet the requirements of UFGS- 03-31-29 and the requirements of transport modeling software STADIUM Lab

Aging functions NIST requires models for structures that have been in place for 40 years. The contractor shall work with NIST to develop mixture proportions to be used in the estimation of aging functions. The contractor shall be responsible for accessing any databases required to estimate aging functions from mixture proportions supplied by NIST. NIST reserves the right to select the appropriate database for this purpose based on observations of materials made during the course of the NCST investigation

Initial Solid Phases The contractor shall work with NIST to develop mixture proportions to be used in the estimation of initial solid phase

Initial Pore Solution Composition

The contractor shall use NIST-supplied mixture proportion information to estimate pore solution ionic concentration.

Boundary Conditions Temperature The contractor shall work with NIST to obtain data to be used in these boundary conditions. This data will be generated during the investigation and supplied to the contractor

Humidity

Solution concentration at surfaces

The contractor shall use data collected as part of Task

4.2 to estimate this boundary condition

Geometry Element dimensions Provided by NIST Rebar Cover depths Provided by NIST Rebar counts, sizes, and locations

Provided by NIST for Champlain Tower South Investigation

The output of the service life models shall be the ionic concentration of species as a function of position in the reinforced concrete elements. All model outputs shall be supplied to NIST in raw and processed form. Where appropriate, the contractor shall supply all files generated in the service life modeling software. The contractor shall prepare technical reports detailing the methods used to construct the service life models, the input parameters, assumptions regarding boundary conditions, and the results. The Contractor’s lead engineer shall supervise the perpetration of the reports and prepare technical analysis and interpretation of the results.

3.7 Task 7: Data Collection, Reporting, and Communication

The contractor shall compile the data collected in Tasks 2 through 6 and prepare reports for NIST and the NCST Investigation. The data collected in Tasks 2 through 6 shall be compiled into a dataset which shall contain information describing the collection methods used to obtain the data, location, and identification of the specimens from which the core was extracted. The dataset shall be updated by the contractor as new test results are obtained.

The contractor shall be available by virtual meeting, phone, and email with NIST and NIST contractors to discuss ongoing data collection and interpretation and report preparation. NIST requires at least one virtual meeting, lasting one hour, per week during the period of performance.

The Contractor shall perform the following tasks:

Compile data collected in this scope of overall contract work such that it can be used to develop relationships between NDT conducted on cores and specimens for mechanical property tests. The dataset shall be delivered to NIST as a delimited text file (comma or tab separated) with supplemental reporting on the structure of the dataset, methods of data collection and notes relevant to collection and interpretation.

Attend virtual meetings in support of the execution of Tasks 1 to 7, and optional Tasks 8 and 9 if exercised, and to communicate findings and reports to NIST.

4.0 Optional Tasks

The following requirements are optional requirements which may or may not be exercised at the Government’s discretion in accordance with FAR 52.217-9 and FAR 52.217-7. Optional requirements may be exercised at time of award in accordance with FAR 52.217-4.

4.1 Optional Task 8: Extend Corrosion Potential and Corrosion Rate Mapping by 15 Specimens

Optional Task 8 extends the activities and deliverables of Task 3 to include an additional 15 specimens.

4.2 Optional Task 9: Second Round of Cores for Concrete Transport Properties

Optional Task 9 extends the activities and deliverables of Task 4 for up to additional 50 pucks for ASTM C1585-20, ASTM C1792-14, ASTM C642-21, ASTM C1356-07(2020), and an agreed-upon bulk resistivity test.

5.0 Deliverables

The Contractor shall submit the following deliverables to the NIST COR and NIST Technical Point of Contact (TPOC) per the schedule identified. All materials shall be submitted via email unless otherwise specified in this document or approved in writing by the COR.

The COR will evaluate deliverables for completeness and correctness. In the event revisions to deliverables are required, the COR will provide feedback and the Contractor shall make the revisions. The COR will provide notice when deliverables are accepted. Data rights for all deliverables shall be in accordance with FAR 52.227-17.

Deliverable Description Quantity/Media Date Required

0 Kick-off Meeting Virtual Meeting Within two weeks of award

1 Task 1: Safety Plan Written Report Within two weeks of award

2 Task 2: Report and Recommendations. Written, presentations, attendance in virtual meetings.

Weekly

3 Task 3: Written report and data set Report: MS Word, Data set:

Excel, CSV.

4 months after completing corrosion rate and corrosion potential measurements on the 50th specimen

4 Task 4.1: Written report and data set Report: MS Word, Data set:

Excel, CSV.

2 Weeks after the award date

5 Tasks 4.2, 4.3, 4.4: Written report and data set

Report: MS Word, Data set:

Excel, CSV.

Data set: As collected. Collection to start approximately 3 months after award

Report: 4 weeks after completing Data collection

6 Task 5.1 Written report and data set Report: MS Word, Data set:

Excel, CSV.

2 Weeks after award date

7 Task 5.2: Four concrete slabs per Figure 4.1 ready for natural or accelerated corrosion.

4 concrete slabs 8 weeks after the award date for Champlain Tower South Investigation

8 Task 5.2: Written Report and data set Report: MS Word, Data set:

Excel, CSV.

18 weeks after award date

9 Task 5.3: Written report and data set Report: MS Word, Data set:

Excel, CSV.

Approx. 8 months after award date

10 Task 5.4: Written report and data set Report: MS Word, Data set:

Excel, CSV

Data set: As collected. Collection to start approximately 3 months after award

Report: 4 weeks after completing Data collection on 100 reinforcing bars.

11 Task 6: Service life modeling Report: MS Word, Data set:

Excel, CSV, Computational Model

Final models and reports due within 8 weeks of the start of service life models

12 Task 7: Compile data collected in this scope of overall contract work such that it can be used to develop relationships between NDT conducted on cores and specimens for mechanical property tests. Attend virtual meetings as scheduled.

Data Collection: Delimited text file (comma or tab separated) with supplemental reporting on the structure of the dataset, methods of data collection and notes relevant to collection and interpretation.

13 Optional Task 8

Report: MS Word, Data set:

Excel, CSV.

Corrosion rates and corrosion potential measurements to be completed 4 weeks after exercising option

Report: 4 weeks after completing last corrosion potential measurement

14 Optional Task 9 Report: MS Word, Data set:

Excel, CSV.

Data set: As collected. Collection to start approximately 4 weeks after exercising option

Report: 4 weeks after completing Data collection

6.0 Performance Requirements

Deliverable Associated Task Required Service Performance Standard Monitoring Method

0. Kick off Meeting All Consulting Attendance of virtual meeting COR Review

1. Safety Plan All Report Evaluation by NIST Safety COR Review

2. Suggestions for project meetings and project plans in written or oral form.

Task 2 Consulting on corrosion of steel in reinforced concrete structures.

Attendance of virtual and in-person meetings. Timely responses to requests for information.

COR Review

3. Written report containing corrosion potential maps and corrosion rate estimates and raw and processed data.

Task 3 Obtain corrosion potential and corrosion rate measurements.

Corrosion potentials obtained via ASTM C876-15.

Reporting plots and figures of corrosion potential and corrosion rate measurements to be reviewed by the

COR.

4. Written experimental Plan for measuring transport properties.

Task 4.1 Development of a plan to measure transport properties of concrete extracted from evidentiary building debris.

ASTM test associated with desired transport properties.

ASTM C1152-20, ASTM

C1556-11a(2016).

Draft report submitted for review by the NIST COR. Revisions to draft report will be reviewed by the COR after comments from NIST are addressed by the Contractor. Final report approved by COR.

5. Written report and database of measured concrete transport properties and raw data from tests.

Tasks 4.2, 4.3, and 4.4

Obtain transport properties of concrete

ASTM test associated with desired transport properties.

ASTM C1152-20, ASTM

C1556-11a(2016), ASTM

C1202-19, ASTM C1356-

07(2020), ASTM C1585-20,

Reports and weekly written status updates to COR.

for Champlain Tower South Investigation

ASTM C1792-14, ASTM

C642-21

6. Written experimental plan for accelerated corrosion testing.

Task 5.1 Development of an experimental plan to accelerate the corrosion of reinforcing bar in concrete resembling CTS slab concrete.

Technical review by NIST of submitted experimental plan.

Reports and weekly updates to COR.

7. Report of concrete properties

Task 5.2

Report on fresh and hardened properties of concrete used to create slab specimens.

Technical review of report by

NIST.

Weekly updates and data reporting to

COR.

8. Four concrete specimens for accelerated corrosion testing.

Construction of four reinforced concrete slab specimens for accelerated corrosion

Technical review of construction by NIST.

Weekly updates and data reporting to

COR.

9. Witten report and database of acquired data of corrosion of reinforced concrete slabs.

Task 5.3 Written report and raw and processed data of accelerated corrosion of reinforced concrete slabs.

Technical review of report and data by NIST.

Weekly updates and data reporting to

COR.

10. Written report and data set of mass loss of corroded reinforcing bar

Task 5.4 Written report and raw and processed data of accelerated corrosion of reinforced concrete slabs.

Technical review of report and data by NIST.

Weekly updates and data reporting to

COR.

for Champlain Tower South Investigation

11. Service life models source files and results

Task 6 Written report and raw and processed data of accelerated corrosion of reinforced concrete slabs. All files created while using service life prediction software

Technical review of report and data by NIST.

Weekly updates and data reporting to

COR.

11.12. Compile data

collected in this scope of overall contract work such that it can be used to develop relationships between NDT conducted on cores and specimens for mechanical property tests. Attend virtual meetings as scheduled.

Task 7 Provide compiled data collection and attend and participate in virtual meetings as schedule

Data is accurate, submitted in the required format.

Meeting attendance and participation is timely and productive

COR Review

13. Written report containing corrosion potential maps and corrosion rate estimates and raw and processed data.

Optional Task 8 Obtain corrosion potential and corrosion rate measurements.

Corrosion potentials obtained via ASTM C876-15.

Reporting plots and figures of corrosion potential and corrosion rate measurements to be reviewed by the

COR.

14. Written report and database of measured concrete transport properties and raw data from tests.

Optional Task 9 Obtain transport properties of concrete

ASTM test associated with desired transport properties.

ASTM C1152-20, ASTM

C1556-11a(2016), ASTM

C1202-19, ASTM C1356-

07(2020), ASTM C1585-20,

Reports and weekly written status updates to COR.

for Champlain Tower South Investigation

ASTM C1792-14, ASTM

C642-21 for Champlain Tower South Investigation

7.0 Government-Furnished Property, Material, Equipment, or

Information (GFP, GFM, GFE, or GFI)

Upon award, the Government will provide the contractor with a template to format technical reports and a style guide to include instructions on formatting technical documents published through NIST.

The contractor will be provided access to investigative materials through NIST’s network. The Government will not provide any equipment to the contractor. All equipment, including computing and telephone equipment, is the responsibility of the Contractor. The Government will not be responsible for cell phone charges associated with contract performance.

NIST will provide the Contractor with the necessary materials and information to formulate concrete used for accelerated corrosion testing.

NIST will provide the Contractor with Type A, B, and C cores for transport property measurements.

NIST will provide the Contractor with the information for service life models in accordance with Table 4.2.

NIST will provide the contractor with materials and instructions to formulate the concrete for the specimens detailed in Task 5.

All property, data and information provided by the Government in the performance of this task remains the property of the Government and shall be surrendered to the Government upon completion or termination of this requirement. Likewise, all deliverables generated under this requirement remain the property of the Government.

8.0 Risk Levels

The work to be performed under this contract will be IT Low Risk and Non-IT Low Risk.

9.0 Travel

Travel is required to conduct investigative research in Miami and/or Surfside, FL. Additional travel may be required to Gaithersburg, Maryland for meetings at the NIST campus, to meet with NIST’s Structural Contractor, and to meet with the BOR. Travel, when approved in advance by the NIST COR, will be reimbursed in accordance with the Federal Travel Regulation.

The Contractor shall be responsible for making all travel arrangements, including but not limited to airline tickets, hotel, car rental reservations, etc. All travel must be in accordance with the Federal Travel Regulation and pre-authorized by the COR. The Contractor shall make every effort to keep travel costs to a minimum and shall not exceed a negotiated travel ceiling for all requirements within the SOW.

10.0 Key Personnel Requirements

The contractor shall provide as key personnel one (1) lead engineer or scientist to serve as a corrosion expert. The key personnel shall meet the minimum requirements identified below.

for Champlain Tower South Investigation

Note that the labor category titles identified in this Statement of Work are not mandatory; they are simply examples of titles suitable to the type of work to be performed by the key personnel position.

One (1) Corrosion Expert

Minimum Education: Ph.D. degree from an accredited college or university in Material Science/Mechanical Engineering/ or Civil Engineering

Minimum Experience: 25 years of experience in evaluation of steel corrosion in concrete and concrete durability which includes conducting laboratory experiments to obtain data that is used as input to service life modeling; developing, executing, and interpreting results of service life prediction model; experience measuring degree of corrosion by mass loss on rebar sections;

participation developing standardized test methods to assess the corrosion severity of steel and the service life of reinforced concrete; and participation in standard writing organizations related to the durability of reinforced concrete infrastructure.

Responsibilities: Applies technical knowledge and judgment in a scientific or another technical field in relevant engineering principles and practices as required for technically complex assignments. Develops procedures and experimental methods to obtain data for service life modeling, estimating the degree of corrosion, and diagnosing durability problems in reinforced concrete structures. Uses engineering/scientific tools to integrate requirements and solve technical problems.