View photos of the restoration process.
The Memory sculptures are part of an entire bridge designed to commemorate the veterans of World War I. In 1930, Chicago sculptor Emory P. Seidel designed the original plans for the bridge. As a period publication stated, using an artist made the bridge "remarkable in its beauty and unique in its design...which will help bring realization that bridges need not be as drab as gas tanks, telephone poles and other things that must be put up with along public thoroughfares."
Completed in November 1931, the Memory sculptures include four concrete figures capping the piers of the bridge, two at each end in mirror image. Each statue shows a hooded female figure in a kneeling position, her eyes closed in retrospection. One hand rests on a plain slab in front of her holding a wreath. Her other hand, resting in her lap, clasps a helmet of the dough boy type. The figures rise 10 feet 6 inches above the sidewalk level, while the folds of their robes flow down the piers, incorporating them into the structure of the bridge.
Condition Before Restoration
Prior to the restoration in 2002, the Memory sculptures were exposed to an outdoor environment for over 60 years without conservation treatment. They were experiencing surface deterioration from dirt, salts, and the freeze thaw cycles. Further erosion was caused by the broken drainage system in each lap of the sculptures, causing water to flow through cracks in the sculptures rather than out the drainage system. Repairs from the 1991 reconstruction left a gap at the street level that allowed water infiltration into the piers resulting in deterioration. There was also discoloration in the surface treatment between the piers and sculptures.
Non-destructive impact-echo, impulse radar and R-meter testing were completed on the sculptures to evaluate the condition of the concrete. They also would detect the presence of reinforcing steel that could be corroding and causing damage. The impact echo test uses low frequency mechanical energy to rapidly detect, locate and classify discontinuities within hardened concrete. This test method is based on the physical laws of elastic stress wave propagation in solids. In this test method, a mechanical impactor and a wide band transducer are positioned on the same face of the test object. The impactor is used to generate a broad band stress pulse within the hardened concrete. Waves of mechanical energy are reflected from the opposite boundary of the test object or form defects which may exist in the test object. Reflected energy is received by the transducer, and processed with Fast Fourier Transform (FFT) frequency analysis algorithms by a dynamic signal analyzer. Reflections are indicated by frequency perks in the resulting spectral plots of amplitude versus frequency. The results indicated that large voids do not exist within the concrete comprising any of the four Memory sculptures.
The R-meter (also called a pachometer or covermeter) is a handheld instrument that uses magnetic methods to locate steel reinforcement embedded in concrete. Through calibration, the depth of concrete cover to the reinforcement and reinforcing bars size can be estimated. The impulse radar operates on the principals of electromagnetic wave reflection. A small contacting transducer transmits electromagnetic pulses into the test element. These pulses are partially reflected back to the transducer by the interfaces between materials of different dielectric constant (concrete in this case). The greater the difference in dielectric constant, the greater the intensity of the reflected pulse. The remaining portion of the pulse is refracted into the next medium, where more of the pulse can be reflected. Reflected pulses are received by the transducer, electronically processed, and displayed. The location of an object is determined by the amount of time between pulse transmission and reception, and the wave propagation speed in the test element.
R-meter and impulse radar testing confirmed the presence of reinforcing steel connecting the bridge railing to the adjoining sculpture. Due to the geometry of the sculpture, the depth of penetration of this steel could not be determined. However, based upon visual inspection, and test results, it was determined that the steel did not pose a threat to the sculptures. A metal anchor was also found in the helmets of the sculptures. Impact echo testing detected the presence of a horizontal crack or disbondment within the helmet, however, the consultant indicated that it was not posing a threat to the sculpture. The echo testing also indicated that large voids do not exist within the concrete comprising any of the four sculptures. The impulse radar test also confirmed the result of the impact echo and R-meter testing. This information, coupled with the CTL Microscopical Examination taken from a concrete sample, lead the consultants to recommend that the sculptures were in fair to good condition, and could be restored.
The treatment was completed by Conservation of Sculpture and Objects Studio. First the sculptures were cleaned with steam in the range of 100 to 200 psi. Then Bio-klean, a biocide containing sodium hydroxide and amine oxide which destroys any living organism from the cement surface, was used as a two part system. First, an alkaline wash was sprayed on and removed with steam. Then, a weak organic acid wash was applied to neutralize the surface which was again rinsed with steam. Areas of delamination were consolidated with Paraloid B-67, a resin consisting of acrylic copolymer and small amounts of monomers and toluene. Cracks and fissures ranging from 1/16 inch and larger were injected with M-30-Jahn injection mortar comprised of silicon dioxide, non-hazardous aggregates, tricalcium silicate, dicalcium silicate, tricalcium aluminate, calcium oxide, and inorganic pigments. The drainage system in the sculptures was repaired to prevent further deterioration and to properly avert water away from the sculptures. Finally, a coating of H 40, a siloxane water repellent was applied to the sculptures to prevent future damage from salt and pollutants. The coating allows moisture to pass through from the inside of the sculptures, thus preventing moisture from being trapped and causing surface deterioration. The treatment is in accordance with the Secretary of Interior Standards for Restoration, and has been approved by the Illinois Historic Preservation Agency as a requirement for the TEA21 funding.
For the surface conservation, a cement based repair material was developed to match the original concrete. It was necessary to have the new repair concrete weaker than the original material because the weaker material will fail before it does any damage to the original substrate. In order to provide structural strength of the new repair material and proper bond to the surface, titanium pins were inserted into the original concrete along with wire. This will increase the longevity of the repairs. The sculptures were then coated with Sure Kean - Weather Seal H40 Water Repellent - a siloxane-based water repellant manufactured by Pro So Co comprised of petroleum.
The drainage pipes in each sculpture were filled with Paraloid B-67 in Acetone for 30 minutes, and then allowed to drain in order to prevent future corrosion of the ferrous pipes. The piers were coated with a lime wash to match the original color since the 1990 repairs included a new thick coating of concrete that could not be removed.
Following the conservation treatment, molds were taken of the sculptures, and from the molds positives were formed using the West Epoxy system. The positives were then placed at the Illinois Math and Science Academy to remain until such time as repairs are needed in the future. In that event, they will serve to make molds of deteriorated portions of the sculptures.