- Author
-
Stutzman, P. E.
|
Clifton, J. R.
- Title
- Diagnosis of Causes of Concrete Deterioration in the MLP-7A Parking Garage.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Report
-
NISTIR 5492,
June 1994,
17 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
alkali-silica reaction
|
building technology
|
concretes
|
cracking
|
deterioration
|
expansion
|
petrography
|
water repellents
- Abstract
- Parking garage MLP-7A at the National Institutes of Health (NIH) is a four-level, cast-in-place concrete structure, approximately seventeen years of age which is exhibiting expansion and cracking of the parapet walls. Field inspection, petrographic analysis of concrete cores and laboratory testing are being used to identify the processes responsible for expansion and cracking of the concrete, to determine the potential for additional expansion, and to evaluate the abilities of several commercially available water repellents applied to the concrete surface to reduce water infiltration. Evidence of alkali-silica reaction was observed in core samples extracted from the parapet walls, an inside wall from the lower level, and in the upper deck as one or more of the following; crack-filling, void-filling, or aggregate-rimming reaction gel. The quantity of reaction gel is greatest in cores removed from the upper, more exposed portions of the structure. The non-uniform distribution of entrained air voids observed in some of the cores is a result of their infilling due to precipitation of calcium hydroxide, ettringite, and gypsum and may result in poor freeze-thaw resistance. An accelerated expansion test of aggregate extracted from the structure indicates that the aggregate is reactive and that there is a potential for further expansion. The performance of water repellant treatments were evaluated in field studies on the garage structure. Each repellant treatment reduced water infiltration relative to an untreated test region however, some treatments performed better in regions with visible, fine surface cracks.