B08_Attach 3 Report 5_Mortar Evaluation.pdf

Atkinson-Noland & Associates

2619 Spruce Street

Boulder, CO 80302

303.444.3620

32 Old Slip, 10th Floor

New York, NY 10005

917.647.9530 ana-usa.com

MORTAR EVALUATION

September 6, 2019

Prepared For

Speweik Preservation Consultants, Inc.

3163 Heritage Pkwy

Elgin, IL 60124

224-856-7449

Prepared By

Atkinson-Noland & Associates, Inc.

2619 Spruce Street

Boulder, CO 80302

303.444.3620

Crater Lake National Park Mortar Analysis

ANA Job No. 19-132

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Introduction

One mortar sample was sent by Speweik Preservation Consultants from the 1932 Steel Visitor Center at

Crater Lake National Park and tested in the Atkinson-Noland & Associates (ANA) laboratory for mortar composition. The objective was to identify binder/aggregate ratio, aggregate color, and aggregate size gradation to provide an appropriate compatible replacement mortar formulation.

Analysis Techniques

Two analysis techniques were used. The chemical mortar examination followed the method described in

Chemical Characterization of Historic Mortars by Middendorf, et al1. This method is based on the use of acid digestion and chemical analysis to identify soluble silica resulting from portland cement hydration.

Additionally, aggregate sieve analysis followed the requirements of ASTM C136, Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates. This method is based on the use of acid digestion of the binder and sieve analysis of the aggregate.

Table 1. Sample identification and location

Sample ID Location

S1 1932 Steel Visitor Center, West Elevation

Analysis Results

The results of the chemical analysis and acid digestion of the sample are shown in Table 2 and Table 3, respectively. The binder component was found to be approximately 40%, and the aggregate component was found to be approximately 60%, and results show that the mortar formulation most closely matches that of a cement sand mortar. Sample S1 consists of essentially a portland cement-sand mix. This finding was confirmed by the hard nature and relative difficulty of crushing of the mortar sample.

The aggregate gradation curve, plotted in Figure 1, shows that the aggregate from S1 falls within the gradation range of coarse and fine aggregates as specified by ASTM C144, Standard Specification for

Aggregate for Masonry Mortars, except for a greater proportion of coarse aggregates retained on sieve size #4 and #8 and greater proportion of fine aggregate passing through sieve size #50, #100, and #200.

This will likely require the incorporation of additional coarse aggregate greater than 2mm and the removal of a portion of less than 0.5 mm aggregate from standard ASTM C144 masonry sand, in order to match the original texture. Table 4 shows the aggregate gradation by percent passing each standard sieve size.

The aggregate size distribution and colors are shown in Figure 2. Ideally, the aggregate for the replacement mortar should match the color and gradation of the existing aggregates. Trial mixtures may be required to produce a repair material that matches the original with respect to color and texture.

1 Middendorf, et al. Chemical Characterization of Historic Mortars. State-of-the-Art Report of RILEM Technical Committee 167-COM:

Characterization of Old Mortars with Respect to their Repair. RILEM Publications SARL, 2004.

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Recommended Mortar Formulation

Mortar used for repointing joints, crack repair, and rebuilding should meet requirements of ASTM C270, Standard Specification for Mortar for Unit Masonry, for Type S mortar, with volumetric proportions of 1 part portland cement, 1/2 parts lime, and 3-1/2 to 4-1/2 parts sand. ANA does not recommend the use of a straight sand-cement mortar for repointing. This type of formulation is difficult for masons to work with, and it will be difficult to maintain an appropriate moisture content in mortar of this type.

The use of pigments may be required to match the hardened mortar color. Pigments conforming to

ASTM C979, Standard Specification for Pigments for Integrally Colored Concrete, are suitable for mortar, but should not exceed 5% by weight of binder content in the mortar. It is also possible that the use of white portland cement will be required in lieu of typical gray cement in order to match the existing mortar color. Trial mixtures may be required to arrive at a mix that matches the original mortar with respect to color and texture.

Table 2. Results of chemical mortar analysis

Sample ID

Sample

Mass

(g)

Aggregate

Mass

(g)

Soluble

Silica

(g)

Volumetric Ratio

Portland

Cement Lime Aggregate

S1 10.00 6.15 0.6 1 1 3

Table 3. Results of acid digestion of mortar samples

Sample

ID

Mass before acid digestion

(g)

Mass after acid digestion

(g)

Binder mass

(g)

Aggregate mass (g)

Aggregate volume

(cm3)

S1 58.51 41.50 17.01 41.50 32.38

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Figure 1. Aggregate distribution by sieve size for mortar sample.

Sieve Size: 4 8 16 30 50 100 200 Pan

Figure 2. Aggregate distribution and color for mortar sample.

48163050100200

0.01 0.1 1 10

0.01 0.1 1 10

Particle Size (mm)

P er ce n t P as si n g

Sieve Number

Crater Lake National Park, 1932 Steel Visitor Center The gradation range specified for masonry mortar in ASTM C144 is indicated in dashed lines.

ASTM C144 Coarsest

ASTM C144 Finest

West Elevation

S1

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Aggregate Gradation Summary

Table 4. Aggregate gradation by percent passing each sieve.

Sieve #

Sample mass (g)

Mass passing (g) % Passing

4 5.67 35.17 86.1

8 1.09 34.08 83.4

16 3.44 30.64 75.0

30 6.61 24.03 58.8

50 9.69 14.34 35.1

100 7.93 6.41 15.7

200 3.32 3.09 7.6 pan 3.09 0.00 0.0