Tension tests were carried out to investigate the effect of the corrosion pattern on the ductility of tension bars extracted from a 26-year-old corroded reinforced concrete beam. The tensile behavior of corroded bars with different corrosion patterns was examined carefully, as were two non-corroded bars extracted from a 26-year-old control beam. The results show that corrosion leads to an increase in the ratio of the ultimate strength over the yield strength, but reduces the ultimate strain at maximum force of the
reinforcement. Both the corrosion pattern and the corrosion intensity play an important role in the ductile properties. The asymmetrical distribution of the corrosion around the surface is a decisive factor, which can influence the ultimate strain at maximum force more seriously.
corrosion; tensiontest; ductility; ultimate elongation; steel bar
Wenjun Zhu and Raoul Francois: Universite de Toulouse, UPS, INSA, LMDC (Laboratoire Materiaux et Durabilite des Constructions), Toulouse, France
The first part of this two-part paper discussed some basic considerations on bond strength and its effect on strain localization and plastic deformation capacity of cracked structural concrete, and analytically evaluated the impacts of the hardening behavior of reinforcing steel and concrete quality on the basis of the Tension Chord Model. This second part assesses the impacts of the most frequently encountered construction details of existing concrete structures which may not satisfy current design code requirements: bar ribbing, bar spacing, and concrete cover thickness. It further evaluates the impacts of the additional structure-specific features bar diameter and crack spacing. It concludes with some considerations on the application of the findings in practice and an outlook on future research needs.
The performance characteristics of high-strength and high-performance concrete are discussed in this review. Recent developments in the field of high-performance concrete marked a giant step forward in high-tech construction materials with enhanced durability, high compressive strength and high modulus of elasticity particularly for industrial applications. There is a growing awareness that specifications requiring high compressive strength make sense only when there are specific strength design advantages. HPC today employs blended cements that include silica fume, fly ash and ground granulated blast-furnace slag. In typical formulations, these cementitious materials can exceed 25% of the total cement by weight. Silica fume contributes to strength and durability; and fly ash and slag cement to better finish, decreased permeability, and increased resistance to chemical attack. The influences of various mineral admixtures such as fly ash, silica fume, micro silica, slag etc. on the performance of high-strength concrete are discussed.
high performance concrete; high strength concrete; mineral admixtures; curing
A.K. Parande: CSIR-Central Electrochemical Research Institute, Karaikudi-630 006, Tamil Nadu, India
The use of post-compressed plates (PCP) to strengthen preloaded reinforced concrete (RC) columns is an innovative approach for alleviating the effects of stress-lagging between the original column and the additional steel plates. Experimental and theoretical studies on PCP-strengthened RC columns have been presented in our companion papers. The results have demonstrated the effectiveness of this technique for improving the strength, deformability and ductility of preloaded RC columns when subjected to axial or eccentric compression loading. An original and comprehensive design procedure is presented in this paper to aid engineers in designing this new type of PCP-strengthened RC column and to ensure proper strengthening details for desirable performance. The proposed design procedure consists of five parts: (1) the
estimation of the ultimate load capacity of the trengthened column, (2) the design of the initial pre-camber displacement of the steel plate, (3) the design of the vertical spacing of the bolts, (4) the design of the bearing ends of the steel plates, and (5) the calculation of the tightening force of the bolts. A worked example
of the design of a PCP-strengthened RC column is shown to demonstrate the application of the proposed design procedure.
reinforced concrete column; pre-cambered steel plate; axial load capacity; design procedure; worked example
L. Wang: College of Civil Engineering, Nanjing University of Technology, Nanjing, China
R.K.L. Su: Department of Civil Engineering, The University of Hong Kong, Hong Kong