Judd works in concrete inspection and field testing
Terra Mare Conservation, LLC (TMC) was contracted by the Chinati Foundation to undertake a site visit to assess the condition of 15 untitled works in concrete (1980–1984) by Donald Judd. The assessment was carried out on April 10–16, 2019, by conservators Claudia Chemello and Paul Mardikian, with Chinati’s Director of Conservation Shelley M. Smith and Chinati’s conservation department intern, Christopher Gonzales.
The objective of this assessment was to obtain an understanding of the present state of preservation. The extensive existing documentation was reviewed to help understand the ongoing effect of fabrication defects and remedial work carried out at the time of production; effects of natural aging and weathering; the impact of human and wildlife interaction; the effects of the site on the works; and the successfulness of the last conservation treatment campaign that extended from 2004–2011. The inspection of each unit helped conservators to identify urgent conservation needs and recommend appropriate remedial conservation treatments. From this, we were able to identify some underlying causes of deterioration and provide guidance on pursuing additional necessary investigation needed for a complete diagnosis.
In general, the surfaces have persistent surface soiling and deep-seated staining, therefore, a particular focus was placed on cleaning, application of migratory corrosion inhibitors, and water-repellency tests. There is a potential for structural instability from inherent structural weaknesses and from the corrosion of steel components. Mild steel is present in the reinforcing steel bars (rebar) within the slabs, square steel tubes embedded in the slabs serve as connectors, and rebar and exposed steel fasteners in the footings. Several footings are exposed to oxidizing conditions because of soil erosion.
The assessment included:
- Visual inspection of all 60 concrete forms and several exposed footings to identify and describe the various condition issues.
- Partial excavation of several select footings to examine the general condition of the concrete, steel plates, and fasteners for groups 1–6 and 7–15.
- Reviewed available archival fabrication records and film footage in Judd Foundation and Chinati Archives.
- Reviewed previous conservation treatment documentation from Chinati Foundation Conservation Department records.
- Performed cleaning tests to evaluate products and procedures needed for the successful removal of surface dirt and organic stains from bat guano and urine.
- Performed water repellency tests to detect the presence of older coatings.
- The conservators tested two products compatible with the existing coating to provide anti-graffiti and water-repellency protection.
We identified three key issues during the assessment that should be addressed to ensure long-term preservation:
1. Corrosion in the concrete slabs and footings. The steel support plates and anchor bolts in the footings of units 7–15 are corroding. The thickening corrosion products put increasing pressure on the adjacent exterior edges of the concrete floor slabs. The pressure eventually causes the concrete to crack and spall off. Corrosion remediation of the concrete slabs is required as soon as possible to prevent corrosion from spreading to the internal rebar.
We did not see any visible sign of a widespread problem with corrosion of the embedded reinforcing steel rebars. When this type of deterioration is severe, it has a specific and characteristic surface crack pattern. Although we did observe some corrosion of the projecting rebar dowels that poke through horizontal slabs in groups 7 to 15 where corrosion was visible on the capped rebar ends. The presence of this corrosion may represent the start of a hidden, widespread problem in the double rebar used in the construction of this group and should be investigated.
2. Soil Erosion. Water drainage across the 1-kilometer site varies because it is in a natural draw or basin with the lowest point between groups 7–15. The site was modified over one hundred years ago for use as a polo field by the military. Ranchers later used it for growing cash crops. The most barren low point experiences the worst annual splash and sheet water erosion. Fledgling vegetation is stripped away upon raindrop impact on exposed soils, and rainwater flows quickly from Chinati’s barracks that are situated uphill. During annual heavy rains, water sheets down across the exposed soil plain carrying soil particulates with it as the water makes its way towards the creek. The absence of vegetation is the chief cause of worsening soil erosion.
Soil erosion around the footings increases the corrosion problem by exposing the concrete and steel to water and oxygen. Erosion undermines the foundations in several ways: as mentioned, it provides pathways for moisture penetration and for water to flow. These voids in the soft soil beneath each unit encourage increased animal burrowing, thereby compounding the problem. Replacing the soil underneath all units with a harder material such as gravel or caliche would facilitate drainage around the footings and prevent animal burrowing. Examining and addressing water drainage of the entire site is recommended as soon as possible.
3. Bats Roosting. Roosting bats inside specific units causes aesthetic, chemical, and structural damage to the concrete. The most obvious damage is the disfiguring urine stains that are extremely difficult to remove, and thick guano where they roost. The urine and guano are extremely corrosive. They will eventually cause pitting and etching of the concrete, as well as corrosion of the embedded steel rebars. Bat mitigation and stain removal are suggested as soon as possible.
Recommendations for treatment strategies to mitigate the three key issues, and associated problems, fall into two phases:
PHASE: Short-term Priorities: (2020–2021): Five priority tasks are recommended for this phase. The sequencing of these tasks is addressed in the forthcoming report in December 2019.
PHASE 2: Long-term (2022–2025): Three priority projects are recommended for this phase. The sequencing of these tasks is addressed in the forthcoming report in December 2019.