During concrete construction, form oil, bond breaker, concrete splatter and other types of contaminants often contaminate reinforcement. Current specifications and quality control measures require the removal and clean up of these contaminants before the placement of concrete due to a concern of a reduction in bonding capacity. This is costly, labor intensive, and may not be necessary. Currently, there is limited research on the effect of reinforcing bar contami- nation on the bond between the deformed steel reinforcing bar and concrete. Because of this lack of data, specifications are conservative and require the removal of the contaminant. Inspectors often cite ACI 301-96, Standard Specifications for Structural Concrete, which states, When concrete is placed, all reinforcement shall be free of materials deleterious to bond. If it could be conclusively proven that this level of care is unnecessary, the construction industry would benefit greatly. To address the effects of contaminants on bond characteristics of deformed steel reinforcing bars, a preliminary study was completed at the University of Missouri-Rolla. The research program focused on three contaminants often seen during construction: form oil, bond breaker and concrete splatter. Other variables included size of reinforcing bar, strength of concrete and epoxy versus uncoated reinforcing bar. This paper will provide the experimental program and test procedures as well as the test results and observations. The results weal that in the majority of situations tested, the ultimate bond stress was not significantly affected by the three contaminants tested. In some cases, the bond breaker and form oil affected the smaller epoxy coated bars, while the effect of concrete splatter was insignificant.

This paper presents strut and tie models that can be used to determine strength and deformation limits for RC members. Conventional strut and tie models have been used for strength design, but they cannot appropriately address the ductility of members that is important to insure safety under severe cyclic loads. This proposed strut and tie model is constituted to address the end region of flexural members, including plastic hinge regions, and will be the basis for the calculation of deformation and corresponding shear strength as well. The behavior of each component of the strut and tie model is evaluated based on the material properties and stress paths. The elongation of the tie element depending on crack spacing and width is obtained from the bond-slip relationship. The contraction of strut element is simply determined from the properties of concrete. The member deformation is obtained by combining the truss deformation determined from components behaviors with joint rotation, The strut and tie model in this paper will provide useful tools for both the design and evaluation of ductility-required RC members.

The behavior of liquid containing structures (LCS) subjected to seismic excitations is reviewed. The major parameters affecting the response of concrete circular tanks for LCS are discussed. Existing codes aud standards related to seismic design of LCS are reviewed. With the aid of a design example, results of the various design standards are compared. The effects of earthquake load on the behavior of reinforced concrete (RC) tanks are also investigated through a detailed example.

Recycled aggregates used in combination with high-volume fly ash is an example of sustainable construction material because it represents a judicious use of resources by recycling by-products, that results in a lower environmental impact through reduced carbon dioxide emissions and reduced natural aggregate extraction from quarries. Furthermore, the related concrete mixtuns yield satisfactory mechanical performance. The goal of the experimental work reported here was to investigate the effect of recycled aggregate andor fly ash on carbonation and chloride penetration depth, as well as the effect on corrosion behavior of either bare or galvanized steel in cracked reinforced concrete. The concrete mixture contained equal amounts of fly ash and cement. The results show that the introduction of the sustainability concept in concre&e trechnology by using recycled aggregate andor fly ash did not cause any deleterious effects on durability of reinforced concrete specimens in terms of both chloride and carbon dioxide penetration, and reinforcement corrosion in cracked concrete.

The finite-element method is used to carry out parametric analyses on the thermal response of simulated defects in fiber-reinforced polymer (FRP) lami- nates applied to a concrete substrate. The aim is to assess the potential for qualtitative infrared thermography in not only detecting a flaw but also being able to describe its physical characteristics. Three parametric studies are presented, namely: 1) relationship between the thermal input, the maximum signal, and the maximum surface temprature; 2) effects of flaw depth and the number of FRP layers; and 3) effect of flaw width. From these simulations, procedures are established for selecting the thermal input and estimating the flaw depth and width.