Evaluation of Mortar from Historical Building

Short write up:

Prior to rehabilitating this historic building, stakeholders wanted to determine the condition of the mortar used to bind the bricks and obtain any pertinent information to assist the repair effort.
Petrographic analysis of the mortar showed significant irregularly shaped fissures/cracks in an otherwise dense low water content paste. Residual gelatinous hydration product was also noted in the voids of mortar. The mortar was completely carbonated as expected.
The average sand content in the mortar was estimated at about 65%; the combined cement and colored pigment at about 35%.

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Historic H.M. King Building, Corpus Christi.

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Residual mortar on surfaces of extracted bricks.

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Sand extracted from mortar via acid digestion test

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Petrographic photo showing dense cement paste, irregularly shaped cracks (red arrow), voids (yellow arrow), voids with gelatinous hydration products (purple arrow) and sand grains (cream particles