Attachment_6_Acid_Digestion_Analysis_140P8324Q0034_0001.pdf

Characterization of Historic Mortar:

Chief Joseph Cemetery Wall

Nez Perce National Historical Park Joseph, OR 97846

August 15, 2023

Prepared for:

Russ Cash

Archaeologist National Park Service

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Attachment 6 Acid Digestion Analysis

Repair Old Chief Joseph Wall Nez Perce National Historical Park

Chief Joseph Cemetery Wall (Joseph, OR) August 15, 2023

Phone: 215-536-6706 3145 State Road, Telford, PA 18969 Website: www.LimeWorks.us Fax: 215-536-2281 Email: lab@limeworks.us

Cover Image: "Chief Joseph Memorial Gravesite Project," Oregon Department of Transportation, 2019. Used under CC-BY-2.0. https://flic.kr/p/2hU5FGG

Architectural Conservator

Laboratory Technicians

Report Personnel LimeWorks®.us Laboratory

Anthony R.C. Hita, AIC-PA, MSHP

Maura Buzzendore, BSChem

Melissa Ricchetti

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1.0: Purpose Statement 1.1: Background 1.2: Executive Summary 2.0a: Analytical Summary (Red Mortar) 2.1a: Characterization of Extracted Aggregate (Red Mortar) 2.0b: Analytical Summary (Gray Mortar) 2.1b: Characterization of Extracted Aggregate (Gray Mortar) 3.0: Product Recommendations 4.0: Testing Methodology 5.0: Definitions

Table of Contents

Characterization of Historic Mortar

Section

Section

Section Section Section

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Section 1.0: Purpose Statement The purpose of a basic acid digestion mortar analysis is to determine the approximate proportions of three principal components of historic mortars—aggregate, binder, and fines. Certain additives may also be detected via this method, but their proportions may not be accurately determined. A basic mortar analysis is primarily used to help ascertain general details about composition of a mortar for the purpose of recreating a historic blend or as a prelude to further instrumental analysis. Thus, this test is most useful for identifying whether cement, lime, and sand are present and in what approximate quantities. Acid digestion can be an important part in developing plans for repairing and maintaining historic structures. While this test protocol is useful for distinguishing general characteristics associated with different binders, it is important to note that the test is subjective, and does not produce the same level of accuracy as an ASTM C1324 instrumental analysis. Testing cannot determine several other important factors in mortar which are difficult or impossible to accurately ascertain, including original water mix, mixing and pointing method, rate of drying, or original condition/origin of aggregate. For further information on methodology, please see Section 4.0.

LimeWorks®.us personnel conduct these analyses with care to produce accurate results to the greatest degree possible.

However, it is up to the client to confer with owners, conservators, masons, and/or installers to determine material appropriateness, installation methods, and performance testing of recommended products beyond data provided by the manufacturer. LimeWorks®.us staff will use information gathered during this test to recommend a compatible material from our products and any additional steps or services if necessary or requested. These recommendations can be found in Section 3.0.

Section 1.1: Background

A box of specimens was submitted to LimeWorks®.us by Russ Cash, archaeologist for the National Park Service. The specimens were divided between a red pointing mortar from a pillar and a light gray mortar from the coping of the southeastern section of the wall at the entrance to the Chief Joseph Cemetery in the Nez Perce National Historical Park. The park itself spans a tristate area encompassing northeast Oregon, southeast Washington, and southwest Idaho. The cemetery is in the Oregon portion in Joseph, Oregon.

The Chief Joseph Cemetery is a memorial site dedicated to Nez Perce leader Old Chief Joseph. The site sits alongside Lake Wallowa, an important location for the Nez Perce native peoples. In 1863, Old Chief Joseph (Tiwi-teqis) refused to sign a treaty relocating his people to the Nez Perce reservation. For the next decade, Old Chief Joseph and later his son Young Chief Joseph (Hinmuuttuu-yalatlat) continued to resist, eventually being given special dispensation to stay by US President Ulysses S. Grant in 1873. The arrangement only lasted two years before Brig.

Gen. Oliver Otis Howard attempted to force the Natives off the land in 1876, resulting in a significant regional conflict known as the Nez Perce War which forced the Nez Perce off the land.1

When Old Chief Joseph died in 1871, he was buried near a fork in the Lostine and Wallowa Rivers. Unfortunately, following the relocation of the Nez Perce, settlers desecrated the grave, eventually exhuming the Chief's skull in 1886 and displaying it in a dentists office in Boise, Idaho. In 1923, Oregon historian J.H. Horner received permission from the Nez Perce to exhume the remains of Old Chief Joseph's body and reinter it at this site. The area was named a National Historic Landmark in 1985. In 1939, the Civilian Conservation Corps, using workers from the native Umatilla people, constructed a wall around the cemetery site of coursed boulders. The wall was mortared with sections of red, white, and yellow mortar representing the Umatilla's medicine wheel and capped with poured concrete inset with tools for strength.2 In 2020, a team led by the National Park Service began a process of cleaning, stabilizing, and repointing the wall. The project was funded by the Federal Highway Administration and Oregon Department of Transportation in partnership with the local Umatilla, Colville, and Nez Perce tribes.3

1 Merle Wells and Edwin C. Bears, “National Register of Historic Places Registration Form for Chief Joseph Cemetery,” National Register Nomination (Washington, DC: US Department of the Interior, National Park Service, 1989).

2 Tom Strandberg, “Preserving the Past to Learn in the Future: Chief Joseph’s Memorial,” My Oregon News, January 10, 2020, https://www.myoregon.

gov/2020/01/10/preserving-the-past-to-learn-in-the-future-chief-josephs-memorial/.

3 “National Park Helps Preserve History,” Nimiipuu Tribal Tribune 1, no. 19 (October 2019): 7, https://nezperce.org/wp-content/uploads/2019/10/Vol.-1- Iss-19.pdf.

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.Section 1.2: Executive Summary

Because the details of this report are lengthy, this executive summary section has been prepared in order to summarize the relevant conclusions and recommendations. Reading the full detailed report is highly recommended to understand these conclusions and recommendations to ensure accuracy and agreement with the goals of the project before proceeding.

In this section, “Test Results” summarizes the data from the mortar analysis, “Mix Recommendations” summarizes the kind of mix the client should look for in a replacement mortar, and “LimeWorks®.us Products” lists the products available through LimeWorks®.us that meet or are analog to the recommendations.

Recommendations are based on data from testing and information provided by client. Additional testing may necessitate revised recommendations, and it is the responsibility of the client to arrange such tests if desired or required. Mixes and products are to be considered substitutes for the historic mortar. If the historic mortar needs to be precisely replicated, additional testing according to ASTM C1324 would be required. It is the responsibility of the client to read this report in its entirety and, in consultation with stakeholders or other authorities, determine the suitability of recommended products. Color recommendations are based on submitted samples and may not reflect weathering conditions or variation present on the building. Mock ups are recommended to determine color suitability.

Test Result Mix Recommendation LimeWorks®.us Products

R ed

M or ta r

1 part binder (Portland cement and lime) to 4 parts coarse manufactured aggregate by weight. Pigment added for color.

Probably a modern Type S.

Proportioned cement-lime Type N composed of 1 part white Portland cement, 1 part Type S hydrated lime, and 6 parts coarse sand conforming to ASTM C144. Color with choice of aggregate and/or a UV and alka-li-stable powdered pigment.

No stock color match available.

Were a pre-blended product desired, a custom simulation is required.

G ra y M or ta r

3 parts binder (Portland cement and lime) to 5 parts coarse aggregate by weight.

Proportioned cement-lime Type O composed of 1 part white Portland cement, 2 parts Type S hydrated lime, and 9 parts coarse sand con-forming to ASTM C144. Color with choice of aggregate and/or a UV and alkali-stable powdered pigment.

Recommendation may need to change based on unique circum-stances of the coping and does not claim to address all priorities of the wall or its materials.

No stock color match available.

Were a pre-blended product desired, a custom simulation is required.

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Section 2.0a: Analytical Summary (Red) The reactive and physical characteristics suggest a mortar composed of Portland cement and lime combined with coarse sand with pigment for color in a ratio of 1 part binder (Portland cement and lime) to 4 parts aggregate by weight.

This conclusion was based on the following observations:

Sample Composition:

CaCO3 ~ 6.223% CaMg(CO3)2 ~ 2.896% Solubles ~ 3.342% Aggregate ~ 66.784% Fines ~ 11.458%

Sample Observations:

• Initial Observations: Sample is heavy, jagged, and dense with a deep red color and medium textured yellow, black, and white flecked aggregate particles.

• Color: The sample color corresponded to 7.5R 6/4 pale red.

• Hardness: The sample was dense and hard with a Mohs rating of 9, requiring excessive force and the aid of tools to pulverize with a mortar and pestle. This is consistent with a Portland cement mortar.

• Reactivity: The sample had a moderate initial reaction with minor effervescence, significant off-gassing, and a significant increase in temperature when exposed to a 14% dilution of hydrochloric acid. Follow the reaction, the acid gelled to a thick mucus-like consistency. This is consistent with a Portland-lime mortar.

• Solubles: The moderate solubles and high hardness suggest a binder comprised primarily of Portland cement with some lime present. This is consistent with a Portland-lime mortar.

• Aggregate: Aggregates extracted from the mortar had an average color of 7.5YR 7/2 pale red. Color was heavily distorted by pigment remnants clinging to aggregate particles. The surviving aggregate fell within mortar aggregate grading standards found in ASTM C144. Overall, the aggregate can be characterized as sharp and coarse. Undigested binder was observed in all sieves, a common issue with cement mortars that can make an aggregate appear coarser than usual. For more information on extracted aggregates please see Section 2.1.

• Fines: Fines extracted from the mortar were an average color of 7.5R 4/6 red. The aggregate was extremely unclean with just over 22% fines. Fines appear to be a mixture of pigment, undigested binder, and crushed stone.

• Filtrate: No unusual filtrate properties were observed, but acid filtering took much longer than usual due to the gelled solution resulting from the digestion of the binder.

• Other Notes: While this test suggests the presence of both Portland cement and pigment, it cannot objectively characterize these materials. Were knowing more about the nature of the cement or pigment necessary, an instrumental analysis according to ASTM C1324 would be required.

Photograph of the bulk sample before digestion (fluorescent light, color corrected).

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Section 2.1a: Characterization of Extracted Aggregate (Red) Because aggregate is an important portion of mortar, helping not only to determine material performance, but also in simulating historic color and texture, this mortar analysis includes a careful examination of aggregates extracted following the acid digestion of the sample. Analysis included a visual analysis and evaluation of particle size. This data can be used to both simulate a historic mortar and/or assess the potential properties imparted by an aggregate blend.

It is important to note that certain portions potentially present in aggregate (such as crushed limestone, marble, and certain silicas) are fully or partially soluble in acid. These are included within a broad category of “solubles.” Solubles would require further instrumental analysis to accurately characterize.

Aggregate particles were mostly white to yellowish-white with some darker brown or black particles. However, due to the abundance of red pigment, color observations were heavily distorted resulting in an overall average color in the Munsell system of 7.5R 7/2 pale red.

Average particle shape varied from very elongate to subequant in sphericity and very angular to subrounded in roundness.

The sand appears to be a manufactured sand, an observation also supported by the large amount of stone fines in the mortar.

Particles were distributed on a bell-shaped curve from the #16 to #200 sieve, with a majority of aggregate captured on the #50 mesh. The fineness modulus of this aggregate was 2.330, indicating a coarse sand. The sand met ASTM C144's grading requirements for a coarse masonry sand. For detailed definitions of these terms, please see section 5.0.

The aggregate contained abundant undigested binder clumps. These clumps hold together smaller particles and pigment which distorts aggregate color and can make it appear coarser than it actually is.

Photomicrograph of the bulk sample before digestion (incident daylight-bal-anced light, 10x magnification).

Photomicrograph of the extracted aggregate before sieving with undigested binder particle (B) examples indicated (incident daylight-balanced light, 10x magnification).

B

B

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Extracted aggregates were sieved according to ASTM C136. Material was passed through a US Standard Sieve Stack (as governed in ASTM E11) and material retained on each mesh was recorded by weight and expressed as a percentage of the whole to determine approximate grading of the aggregate. Results are as follows:

Aggregate Grading:

Sieve Number #4 #8 #16 #30 #50 #100 #200 Pan

Screen Size 4750µm 2360µm 1180µm 600µm 300µm 150µm 75µm ≥25µm

Aggregate Retained 0.000% 0.000% 10.105%* 34.506%* 36.602%* 15.906%* 3.144%* 0.524%*

*Indicates a sieve where undigested binder was observed.

Washed and sieved sands sorted according to sieve size (color corrected fluorescent light)

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

110100100010000

Pe rc en t F in er

(P er ce nt

P as sin g)

Particle Size (µm)

Aggregate Profile (Red)

2.330Fineness Modulus=

0%

5%

10%

15%

20%

25%

30%

35%

40%

(#4)

(#8)

(#16)

(#30)

(#50)

(#100)

(#200)

≤25 (Pan)

Pe rc en t R et ai ne d

Particle Size (µm) (US Sieve #)

Aggregate Size By Sieve (Red)

2.330Fineness Modulus=

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Section 2.0: Analytical Summary The reactive and physical characteristics suggest a mortar composed of Portland cement and lime combined with coarse sand in a ratio of 3 parts binder (Portland cement and lime) to 5 parts aggregate by weight. This conclusion was based on the following observations:

Sample Composition:

CaCO3 ~ 20.205% CaMg(CO3)2 ~ 7.206% Solubles ~ 10.928% Aggregate ~ 51.817% Fines ~ 9.844%

Sample Observations:

• Initial Observations: Sample is of moderate hardness and displays areas of what appears to be deterioration marked by delaminating layers. Color is a light bluish-gray with medium texture dark aggregate visible. Occasional white inclusions may be lime nodules. Rust marks appear on sections, which may explain delamination damage from nearby steel or iron swelling and pushing on sample.

pulverize with a mortar and pestle. This is consistent with a Portland-lime mortar.

• Reactivity: The sample had a vigorous initial reaction with significant effervescence, significant off-gassing, and a minor increase in temperature when exposed to a 14% dilution of hydrochloric acid. This is consistent with a Portland-lime mortar with a higher lime content.

• Solubles: The moderate solubles and high hardness suggest a binder comprised primarily of Portland cement with some lime present. This is consistent with a Portland-lime mortar.

• Aggregate: Aggregates extracted from the mortar had an average color of N8.5 white. The surviving aggregate fell within modern mortar aggregate grading standards found in ASTM C144. Overall, the aggregate can be characterized as dull and coarse. Undigested binder was observed in all sieves, a common issue with cement mortars that can make an aggregate appear coarser than usual. For more information on extracted aggregates please see Section 2.1.

• Fines: Fines extracted from the mortar were an average color of N8.5 white. The aggregate was clean with just under 10% fines. Fines appear to be a mix of undigested binder and natural clays.

• Filtrate: Filtrate was slightly more yellow than expected, which may be caused by an oxidation reaction with the rust particles on the sample. Otherwise, the filtrate had no unusual properties.

• Other Notes: While this test suggests the presence of both Portland cement and pigment, it cannot objectively characterize these materials. Were knowing more about the nature of the cement or pigment necessary, an instrumental analysis according to ASTM C1324 would be required.

Photograph of the bulk sample before digestion (fluorescent light, color corrected).

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Phone: 215-536-6706 3145 State Road, Telford, PA 18969 Website: www.LimeWorks.us Fax: 215-536-2281 Email: lab@limeworks.us

Section 2.1: Characterization of Extracted Aggregate Because aggregate is an important portion of mortar, helping not only to determine material performance, but also in simulating historic color and texture, this mortar analysis includes a careful examination of aggregates extracted following the acid digestion of the sample. Analysis included a visual analysis and evaluation of particle size. This data can be used to both simulate a historic mortar and/or assess the potential properties imparted by an aggregate blend.

It is important to note that certain portions potentially present in aggregate (such as crushed limestone, marble, and certain silicas) are fully or partially soluble in acid. These are included within a broad category of “solubles.” Solubles would require further instrumental analysis to accurately characterize.

Aggregate particles mostly grayish-white with some greenish, yellowish-brown, and black particles throughout. Sieve average colors did not vary far from the overall aggregate average color in the Munsell system of N8.5 white.

Average particle shape varied from very elongate to equant in sphericity and subrounded to rounded in roundness. The sand appeared to be natural.

Particles were distributed on a bell-shaped curve from the #16 to #200 sieve, with a majority of aggregate captured on the #30 mesh. The fineness modulus of this aggregate was 2.480, indicating a coarse sand. The sand met ASTM C144's grading requirements for a coarse masonry sand.

For detailed definitions of these terms, please see section 5.0.

The aggregate contained abundant undigested binder clumps. These clumps hold together smaller particles which distorts aggregate color and can make it appear coarser than it actually is.

Photomicrograph of the bulk sample before digestion (incident daylight-bal-anced light, 10x magnification).

Photomicrograph of the extracted aggregate before sieving with prominent undigested binder (B) examples indicated (incident daylight-balanced light, 15x magnification).

B

B

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Extracted aggregates were sieved according to ASTM C136. Material was passed through a US Standard Sieve Stack (as governed in ASTM E11) and material retained on each mesh was recorded by weight and expressed as a percentage of the whole to determine approximate grading of the aggregate. Results are as follows:

Aggregate Grading:

Sieve Number #4 #8 #16 #30 #50 #100 #200 Pan

Screen Size 4750µm 2360µm 1180µm 600µm 300µm 150µm 75µm ≥25µm

Aggregate Retained 0.000% 1.811%* 11.287%* 39.573%* 31.212%* 12.680%* 3.902%* 0.697%*

*Indicates a sieve where undigested binder was observed.

Washed and sieved sands sorted according to sieve size (color corrected fluorescent light)

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Attachment 6 Acid Digestion Analysis

Phone: 215-536-6706 3145 State Road, Telford, PA 18969 Website: www.LimeWorks.us Fax: 215-536-2281 Email: lab@limeworks.us

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

110100100010000

Pe rc en t F in er

(P er ce nt

P as sin g)

Particle Size (µm)

Aggregate Profile (Gray)

2.480Fineness Modulus=

0%

5%

10%

15%

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25%

30%

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45%

(#4)

(#8)

(#16)

(#30)

(#50)

(#100)

(#200)

≤25 (Pan)

Pe rc en t R et ai ne d

Particle Size (µm) (US Sieve #)

Aggregate Size By Sieve (Gray)

2.480Fineness Modulus=

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Section 3.0: Discussion and Product Recommendations

The Secretary of the Interiors’ Standards for the Treatment of Historic Properties recommends replacing a historic mortar with one similar to or less dense than the original for restoration and rehabilitation projects. However, the standards acknowledge that changes in material preparation, new understanding of material properties, and weathering over time may necessitate a mix different than the original.4 These standards were taken into account in the following recommendations. All mortar selections should conform to ASTM C1713, with pointing practices conforming to ASTM E2260.

Red Sample: The red mortar sample has properties nearly identical to a modern Type S masonry mortar and is very likely a modern 21st century mix, probably dating to the 2019-2020 repairs done to this section of the wall.

Mortars of similar proportions to Type N and Type S mortars have been in use since the late 19th century, so testing cannot fully rule out the mortar is older. However, the proportions of the mortar, physical properties, use of a likely manufactured sand, and lack of weathering on the bulk sample all suggest a recent mortar. Furthermore, a test of the mortar using a phenolphthalein indicator showed that it was not yet deeply carbonated, meaning the mortar has either been exceptionally sheltered or is relatively new.

While a mortar similar to a Type S were used in the 1930s when the wall was built, Portland cement today is much more refined than at that time and can result in much stronger and denser cements than even those 30 years ago.

It may be prudent to reduce the strength of repair mortars from a Type S to a more lime-rich Type N to help avoid potential problems arising from high strength modern cement.

ASTM C270 defines a proportioned cement-lime Type N as 1 part Portland cement, 0.5 to 1.25 parts hydrated lime, and sand parts between 2.25 and 3 times the sum of the cement and lime. This is usually simplified to 1 part Portland cement, 1 part Type S hydrated lime, and 6 parts sand. White Portland is recommended for its higher sulfate and salt resistance compared to gray varieties. Sand should be dry, clean, and conform to ASTM C144. Color with choice of aggregate or with UV and alkali stable powdered pigment.

LimeWorks®.us does not have a stock color or blend of stock colors that adequately mimics the look of the submitted sample. Were a pre-blended mortar desired, a custom simulation would be necessary. Please speak to a LimeWorks®.

us sales representative for pricing and timetables for any additional services.

Gray Sample: The gray mortar sample is not neatly identical to the proportions of any modern mix but is closest to a modern Type O masonry mortar. While such a lime rich mortar is unusual for coping mortar, the coping on this particular wall is abnormal and so the builders may have used a non-conventional mixture of cement and lime adapted to the context. Portions of the sample show distinct rust marks consistent with the rusting tools in embedded in the coping and likely the reason for the mortar's failure. While a modern Type O may be compatible, the unique construction and historic significance of the coping may warrant further testing before selecting a replacement mortar as the preservation of the in-situ artifacts was listed in several sources as a priority.

Preservation of embedded steel and iron elements depends in part on the high maintained alkalinity and low permeability of cement. Likewise, a coping receives increased weathering than other portions of a wall and may require a more robust mix. As such, the following product recommendation is provided based only on the tested material and is not claiming to authoritatively address all site factors.

ASTM C270 defines a proportioned cement-lime Type O as 1 part Portland cement, 1.25 to 2.5 parts hydrated lime, and sand parts between 2.25 and 3 times the sum of the cement and lime. This is usually simplified to 1 part Portland cement, 2 parts Type S hydrated lime, and 9 parts sand. White Portland is recommended for its higher sulfate and salt resistance compared to gray varieties. Sand should be dry, clean, and conform to ASTM C144. Color

4 United States, Department of the Interior, National Park Service Technical Preservation Services, The Secretary of the Interior’s Standard for the Treatment of Historic Properties, ed. Anne E. Grimmer, 2017, (accessed November 4, 2020, https://www.nps.gov/tps/standards/treatment-guidelines-2017.

pdf), 84.

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Phone: 215-536-6706 3145 State Road, Telford, PA 18969 Website: www.LimeWorks.us Fax: 215-536-2281 Email: lab@limeworks.us with choice of aggregate or with UV and alkali stable powdered pigment.

LimeWorks®.us does not have a stock color or blend of stock colors that adequately mimics the look of the submitted sample. Were a pre-blended mortar desired, a custom simulation would be necessary. Please speak to a LimeWorks®.

us sales representative for pricing and timetables for any additional services.

Please Note: LimeWorks®.us assumes no responsibility for the implementation or success of any work completed based on this report. While analysis suggests the recommended products are appropriate replacements for the tested material, further testing or information not made available to testing parties, specific site conditions, or engineering considerations may necessitate significant deviation from these recommendations. Product recommendations are provided as a good faith courtesy and are not assurances or guarantees. Color recommendations are based on submitted samples and may not reflect in-situ weathering or variation. It is the responsibility of the client and any relevant stakeholders to perform mock ups and determine product suitability. Please speak to a LimeWorks®.us representative to discuss timetables, pricing, and additional testing options if any additional services or products are necessary.

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Section 4.0: Testing Methodology

Testing is completed by an architectural conservator specializing in masonry and with sufficient education and experience to meet the American Institute for Conservation’s qualifications for a conservator and bound by the AIC’s Code of Ethics; or an experienced lab technician under the observation and review of an architectural conservator.

Reports are written by the same and reviewed according to LimeWorks®.us strict quality control standards. All testing is performed in a laboratory conditioned to ASTM C511 specifications for a mortar mixing room.

The approximate composition of the material was determined by referencing the Jedrzejewska analytical method with a calcimeter and techniques conforming to the specifications outlined in ASTM D4373.5 This technique essentially breaks down a sample into constituent parts and provides data on the nature of the binder by gauging the extent of its reaction with hydrochloric acid (HCl). As HCl dissolves bicarbonates of calcium carbonate (CaCO3) and magnesium calcium dicarbonate (CaMg(CO3)2) compounds found in lime and (to a lesser extent) cement binders, carbon dioxide (CO2) is produced. While not absolute and open to a degree of interpretation, by using standard gas/temperature/pressure laws, it is possible to calculate approximate amounts of carbon dioxide released during the acid digestion of the sample providing a reasonable estimation of the amount of carbonates present in the binder of the sample. Data obtained during experimentation was compared with published experimental standards based on known mixes to arrive at conclusions about the composition of all samples.6 This method has its limits, as it can only give an approximation which can be skewed in the presence of certain additives like gypsum, and cannot differentiate between calcium-carbonate and magnesium-carbonate. Aggregates made of acid soluble material such as shells, marble, or limestone may also not be adequately characterized. A certain amount of error can be introduced by the process of crushing the sample for acid digestion, especially in mortars that require a great deal of force to pulverize.

Insoluble portions of the aggregate were retained and washed, while fine particulates of the material were captured in 20-25µm filter paper and retained. The aggregate was dried and weighed, and evaluated according to particulate size with a Standard U.S. Sieve Stack corresponding to ASTM E11 as outlined in ASTM C136. Sorted aggregate was then examined microscopically for particle sphericity, roundness, color, sorting, and other physical properties. Fine particulates, once filtered, were dried, weighed, and examined visually and microscopically. Color classification is performed using the Munsell Color System in accordance with ASTM D1535.

All microscopic examination was conducted using a Nikon® SMZ-2T trinocular reflected light microscope, illuminated by an AmScopeTM 312W-2GOP LED daylight-balanced illuminator. Photographs of samples were captured using a Canon® EOS T5 DSLR camera with a special lens designed to make use of the microscope’s trinocular bay. All photographs were then color corrected using Adobe® PhotoshopTM.

The degree of testing discussed herein is sufficient to establish a basic understanding about the composition of the materials supplied to our laboratory. That said, gravimetric analysis and tests which utilize acid digestion constitute an inexact science, relying substantially on the experience and interpretation of the analyst as well as comparison with materials with known composition. As such, this report should not be interpreted as providing absolute objective composition data on the material. Petrographic analysis including examination of thin sections in transmitted polarizing light and/or elemental analysis would be required to identify mineral phases which are specific to different types of cementing material and to unequivocally quantify the amount of lime and/or cement present. If analysis in accordance with testing procedures described in ASTM C1324 is desired, micro-chemical characterizations may be expanded upon with elemental analysis using techniques such as X-Ray Diffraction (XRD), petrography, and/or physical characterizations of thin sections using transmitted and polarized light microscopy.

5 Hanna Jedrzejewska, “Old Mortars in Poland: A New Method of Investigation,” Studies in Conservation 5, no. 4 (November 1960): doi:10.2307/1505237.

6 James Christopher Frey, Exterior Stuccoes as an Interpretive and Conservation Asset: The Aiken-Rhett House, Charleston, SC, Master’s thesis, University of Pennsylvania, 1997 (Philadelphia, PA: University of Pennsylvania, 1997); John Stewart and James Moore, “Chemical Techniques of Historic Mortar Analysis,” Bulletin of the Association for Preservation Technology, Vol. 14, No. 1 (Washington: APT, 1982), 11-16.

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Section 5.0: Definitions7

• Aggregate: Coarse to fine grained particles that when bound together form the body of a mortar and help control important properties like shrinkage, water content, strength, and durability. They may be manufac-tured from crushing or recycling other materials or extracted from naturally occurring sites such as sand pits or water sources. In mortars, aggregate should not typically interact chemically with other components of the mix and should be appropriately graded for the specified application. Common aggregates include but are not limited to sand, gravel, crushed stone, and inert fillers.

• Binder: A binding agent (or binder) is an essential portion of a mortar which holds all other components together to form a cohesive whole. Mortars generally have two binder classes--hydraulic binders which harden due to interaction with water, and non-hydraulic binders which harden through other means such as crystallization or exposure to air. A non-hydraulic binder can sometimes be made hydraulic through the introduction of a pozzolan. A binder's mechanical and chemical properties play an important role in a mortar including physical properties, anticipated service life, and interaction to environmental factors like temperature, pollution, moisture, and salt.

• Color: A perceived and interpreted spectral composition of light as it interacts with an object or medium.

Because color is subjective, the Munsell Color System attempts to classify the visual experience of color into perceived attributes of hue, lightness, and chroma. These values only apply to opaque samples that are viewed by individuals with healthy color vision in daylight conditions. This method provides a simple, more cost effective alternative to analytical procedures such as spectrophotometry. Munsell notations are given a number-letter-number combination in the form number-letter-slash-number representing Munsell hue (H), Munsell value (V), and Munsell chroma (C). A Munsell color guide also assigns each value an official name. Color classification using the Munsell Color System is performed in accordance to the pro-cedures outlined in ASTM D1535.

• Filtrate: Liquid that passes through a porous medium while separating insoluble solids from liquids. In a mortar analysis, the filtrate is generally composed of dilute hydrochloric acid and soluble compounds freed from the mortar. Filtrate color varies due to interactions between the mortar and the acid used in digestion.

• Fineness Modulus: A numerical representation of the coarseness of an aggregate. The fineness modulus is determined by adding the percentage of aggregate particles retained on the #4-#100 sieves and dividing by 100. The resulting number is an empirical figure characterizing the coarseness of an aggregate sample.

7 Some definitions and figures adapted from: “Characterization of Granular Samples by Sieve Analysis,” Graduate Department of Historic Preservation, HSPV 555, Spring 2016 (Philadelphia: University of Pennsylvania, 2016)

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Generally, the higher the number, the coarser the aggregate. However, because this number can be acquired by different particle size distributions, the fineness modulus alone is not enough to adequately characterize the suitability of a given aggregate.

• Fines: Particles caught on the filtration medium during the process of washing solids released from a mortar digestion. Fines' particle size is typically much smaller than those particles captured on a sieve. In mortars, fines are usually clays, silts, pigments, and other rheological additives. The amount and nature of fines can impact the working properties, color, and final cured properties of a mortar. Unwashed aggregates and pig-mented mortars typically have a high amount of fines.

• Grading: A measurement of how well distributed particulate sizes are within the aggregate of a sample.

Aggregate with a broad, even distribution of grains from small to large is considered well-graded. Grading of materials helps regulate certain properties of a mortar, such as shrinkage, porosity, permeability, and curing behavior. Appropriate grading for modern mortars is governed by ASTM C144, but historic mortars will vary widely from modern specifications. Typically, modern mortar sands will have a fineness modulus between 2.1 and 3.2, with smaller numbers indicating a finer sand and larger a coarser sand.

• Hardness: A subjective measurement of how difficult the mortar is to snap or pulverize. Hardness can also be characterized using the Mohs Hardness Scale, which is a qualitative scale ranking an objects hardness by its resistance to being scratched by harder objects. For example, a sample with a Mohs rating of 5 will be scratched by (but cannot scratch) a 6, while being able to scratch (but not be scratched) by a 4. The Mohs Scale is based on a comparison to the hardness of known minerals. The more hydraulic the material is, the harder it typically will be, meaning cements are usually much harder than lime, gypsum, or clay. Hydraulic limes and cement-lime blends will often fall between the two extremes.

Hardness 1 2 3 4 5 6 7 8 9 10

Mineral Talc Gypsum Calcite Fluorite Apatite Feldspar Quartz Topaz Corundum Diamond

• Pozzolan: Minerals composed of siliceous and aluminous compounds that when combined with calcium hydroxide (Ca(OH)2) found in limes and certain cements will react with water to impart or increase co-hesive properties. Pozzolans may be natural or artificial, and a wide variety of pozzolans have been used throughout human construction history.

• Reactivity: In a mortar analysis, the extent to which a sample responds to contact with hydrochloric acid.

Calcium carbonate, such as that found in lime mortars and calcareous aggregates, evolves a large amount of carbon dioxide (CO2) when exposed to acid, while pure cement-based mortars and gypsum release very little during acid digestion. Limes high in dolomite (CaMg(CO3)2) will have a secondary reaction after the primary calcium carbonate reaction (CaCO3).

• Roundness: An observation of the sharpness of the edges and corners of a particle. A particle that is signifi-cantly worn by abrasion to the point that it appears smooth is considered well-rounded, while a particle that appears cleaved with very sharp edges and little abrasion is considered very angular.

Well Rounded

Very Angular Angular Sub-angular Sub-rounded Rounded

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• Sphericity: Sphericity compares the size of individual particles to how close they approach a perfect sphere. Samples very close to a sphere are said to be “very equant,” while samples that are more distant from spherical are said to be “very elongate.”

• Solubles: Substances which dissolve to form a solution with another substance, usually water or hydrochlo-ric acid (HCl) in a mortar analysis. In an acid digestion mortar analysis, solubles are usually detected by the amount of weight lost on exposure to hydrochloric acid that cannot be quantified by other tests. Pure lime mortars generally have high carbonate but few solubles, while products in cement are acid soluble but do not evolve CO2. Whereas carbonate generally indicates the presence of lime, solubles generally indicate the likely presence of a hydraulic material like cement or pozzolans. So a mortar with low carbonate but high solubles indicates the probable presence of a cement, while moderate solubles and low hardness could in-dicate a hydraulic lime.

• Sorting: Sorting is a description of the degree of distribution of particles of varying size and shape within an individual sample. Samples that are well-sorted have nearly homogeneous size and shape distribution, while those that are poorly sorted have heterogeneous size and shape distribution.

Scale for Aggregate Sorting

Very Poor Poor Fair Good Very Good

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Attachment 6 Acid Digestion Analysis