The case-histories based presentation will focus on the use of nondestructive evaluation (NDE) methods to detect flaws and damage in concrete construction. Case histories will be presented for detection and mapping of flaws and damage in concrete such as cracking, delamination, honeycomb, void, corrosion, fire damage, alkali-silica reaction and low strength concrete. The case histories for the concrete structures are anticipated to include parking structures, bridges, buildings and dams. NDE methods will include sonic/ultrasonic, infrared thermography, radar and corrosion technologies where the results in many cases were confirmed by coring. The use of some of the NDE methods for QA of concrete repairs such as epoxy injection and patching will also be discussed.
Post-tensioned concrete is a strong and durable material for construction of exposed parking structures. These types of structures are also fire resistant, but they can be damaged depending upon the severity of the fire. The structure in this presentation suffered significant fire damage early in its construction. The presentation will cover the discovery and testing methods used to determine the extent of fire damage, and the design of the repairs that were instituted to restore strength and allow construction to continue.
Alkali-Silica Reaction (ASR) can cause significant damage to concrete structures including bridges, roadways, airport runways, and nuclear power plants. When reactive aggregates are included in a mix, the presence of moisture initiates a reaction between the alkaline cement paste and reactive amorphous silica. The result is a gel that continues to dilate, which may cause cracks in the concrete mass. A research program was undertaken at the University of Toronto to investigate the effects of ASR on large-scale and small-scale concrete specimens. Several specimens were constructed using reactive (ASR) concrete and non-reactive (regular) concrete, and their short-term and long-term structural and mechanical behavior were compared. In this presentation, we will discuss the results of the research program, will offer best practices to minimize the risk of ASR in concrete during placement, and will propose several strategies for repair of structures that have been degraded due to ASR.
After only six years of service, a 6-foot long narrow piece of concrete spalled off an exposed slab edge of a 680-foot tall high-rise in Texas, and fell 160 feet to the podium below. The spall was attributed to premature corrosion at the drip edge. The building featured approximately 9,200 feet of exposed slab edge over its height. Given the potential risk to safety and property of additional concrete spalls, the Owner requested forensic investigations, which (1) identified other areas with signs of similar distress and (2) determined the underlying problem of low reinforcement cover at the drip edge was pervasive. In response, repair options were developed to address the problem and restore intended durability. Given the building height, difficult exterior-only access, downtown environment, and post-tensioning anchors along the slab edge, the repair design and construction both had unique challenges to consider and overcome.
The Ituango dam is an embankment dam that is currently under construction on the Cauca River in Colombia. The largest hydroelectric power plant in Colombia’s history. Three large diversion tunnels used to divert the water from the river around the construction site during construction collapsed as a result of heavy rainfalls. The nearly completed pump house had to be flooded to accommodate premature water build-up in the reservoir. These tunnels would need to be permanently sealed. “Pre-stoppers” would need to be constructed in place to serve as bulk heads between which would ultimately be excavated and back-filled with concrete to permanently seal the tunnels. Additional to standard anti-washout properties, the grout had to withstand swiftly flowing water and exhibit an extended working time at temperatures above 32 degrees C. A custom grout was developed for this application. In the end, hundreds of grout micropiles were tremied, consuming more than 1,650 tons of grout, to produce...
Richard Miller Treatment Plant is a 240 mgd cap. potable water treatment facility located in the California area of the Cincinnati, Ohio, US. After installing an advanced ultraviolet (UV) disinfection treatment system in 2013, GCWW became the largest water utility in North America to use UV light following sand filtration and granular activated carbon. The concrete filter gallery building was originally constructed in 1907 with 26 filters, with a 14-filter addition in 1937 and 7 filters added in 1964. After over 110 years of service, the structures started showing significant signs of deterioration, most commonly concrete spalling and reinforcing steel corrosion. This case study will highlight the methods used to evaluate the structures that involved conventional methods such as sounding, crack mapping, chemical and petrographic examinations, along with technology such as Half-Cell Potential/ICOR, Impact-Echo, Ground Penetrating Radar, and UAS (Drone) services.
This presentation looks at buildings that are new or being rehabilitated and the impact on making buildings more energy efficient. Starting with the 2012 IBC, and specifically the 2012 IECC portion of the building code and newer versions, the presentation will look at three aspects of the building envelope: Water Resistance, Air Leakage, and Moisture Transmission. It will then compare to identical buildings, the first built in 2000 and the second constructed in 2020. Illustrations and calculations will show how controlling air leakage can have an enormous impact on the service life of the structure, initial cost of construction, and on-going operations. Lastly, the presentation will look at how incorporating simple additions during the repair/rehabilitation process can have a positive impact on the environment as well as the building owner and the building’s constituents.
Increasingly, the Construction Industry is being dramatically impacted globally by internal and external forces. These influences range from acute labor and skill shortages, demographic and urbanization shifts, as well as, the Industry’s conversion from analog-based processes to digital workflows. This presentation will overview ten significant trends which are uniquely affecting the Construction Industry, creating both new challenges and opportunities, while transforming the Construction Industry.
Arlington Memorial Bridge is a reinforced concrete spandrel arch bridge that connects Washington, DC and Virginia across the Potomac River. After over 85 years in service, the bridge started exhibiting signs of deterioration, including reinforcement corrosion. As part of a major rehabilitation effort to extend the bridge’s service life, targeted cathodic protection (CP) systems were installed in the arch cross-walls, floors, and under arches to mitigate and prevent corrosion. The implemented CP system consisted of galvanic and two-stage anodes to mitigate corrosion. Galvanic anodes were installed in the repair areas to prevent the ring anode affect and ensure a durable concrete repair. The two-stage anodes were installed in areas of concrete which were actively corroding without signs of concrete deterioration.
The presentation, through case studies, talks about emergency response services for structural issues encountered during construction of new design projects. Among other examples is an eleven story precast parking structure. The contractor observed significant diagonal faulted cracking of L-beams (supporting double-tee sections) near bearing locations, few days after pouring topping slab. In addition, inverted-tee girders were observed to be supported on cracked corbels at other locations. A quick turn around was required to mitigate any immediate life safety hazard posed by the structural distresses and buy time for thorough investigation, non-destructive testing, analyses, and repair design. Another example is a seven story precast parking structure. The structure was under construction and reportedly erected out of plumb. Poor concrete placing practices and poor weld detailing led to widespread cracking in multiple structural elements throughout the structure...