Shaikh Faiz Uddin Ahmed

Cover Cracking of Reinforced Concrete Beams Due to Corrosion of Steel

A finite element (FE) model is proposed to simulate the corrosion-induced cracking of reinforced concrete (RC) beams. The smeared cracking approach is used to model the cracking of ordinary concrete, ductile fiber-reinforced cementitious composites (DFRCC), and engineered cementitious composites (ECC). The model simulates the cracking of ordinary concrete beams and RC beams containing ECC and DFRCC materials. The strains obtained from the FE models are compared with that measured by the fiber-optic strain sensor (FOSS) gauge, which is placed between longitudinal steel bars at midspan ofRC beams during the accelerated corrosion test. The model could predict the corrosion-induced damage tolerance of ECC and DFRCC materials and found that it is several times higher than that of ordinary concrete. The model predicted the uniform damage in the ECC and the DFRCC materials due to corrosion compared with localized damage in ordinary concrete. The model also predicted that the delamination of the cover of the RC beams containing ECC/DFRCC materials will occur at a higher level of steel loss compared with that of an ordinary concrete beam. The better performance exhibited by the RC beam containing ECC/DFRCC materials is due to their higher tensile strain capacity, strain hardening, and multiple cracking behavior.

Properties of concrete containing construction and demolition wastes and fly ash

This paper reports the properties of concrete containing recycled coarse aggregate (RCA) sources from local construction and demolition (C&D) wastes and fly ash (FA) sourced from Western Australia (WA). The RCA is used as 25, 50, 75, and 100% (by weight) replacement of natural coarse aggregate (NCA). In addition, the effect of 40% (by weight) class F fly ash as partial replacement of cement on the properties of recycled aggregate concrete is also evaluated. The properties of concrete evaluated are the compressive strength, indirect tensile strength, flexural strength, and water absorption. All properties are measured at 7, 28, 56, and 91 days. The results show that better compressive, tensile, and flexural strength of concrete containing 25% RCA as partial replacement of NCA can be obtained in recycled aggregate concrete. However, in the case of recycled aggregate concretes containing 40% fly ash, the compressive strength at later ages, such as at 56 and 91 days is increased but the indirect tensile and flexural strengths are decreased at all ages. It is observed that the water absorption is decreased as RCA content increased. It is also observed that the water absorption is decreased significantly in recycled aggregate concretes containing 40% fly ash at all ages.

Fiber Optic Sensing for Monitoring Corrosion-Induced Damage:

This paper reports the feasibility of using embedded Fabry–Pé rot fiber optic sensors to detect and monitor the propagation of cracks and delamination within concrete beams induced by corrosion of the reinforcing bars. In this research, four series of reinforced concrete beams were subjected to varying degrees of corrosion-induced damage by modifying the composition of the concrete mix and subjecting all specimens to the same accelerated corrosion environment. The concept employed in this study involves embedding the Fabry–Pé rot sensor between two reinforcing bars to measure the transverse tensile strains associated with the longitudinal crack along the reinforcing bars (and in severe cases, delamination of the concrete beam) resulting from the radial expansion of the corroding rebars. Excellent correlation was obtained between the Fabry–Pé rot strain data and the amount of steel loss resulting from accelerated corrosion. In addition, the optical sensor strain readings and the reductions in the load-carrying and deflection capacities were also observed to exhibit strong positive correlation highlighting the potential of the optical sensor to monitor the progression of the rebar damage and the loss of structural integrity of the beams resulting from the extensive corrosion. The technique used in this study demonstrates the possibility of detecting corrosion-induced damage in reinforced concrete structures, particularly those where visual inspection is not possible.

Mechanical and Durability Properties of Mortars Modified with Combined Polymer and Supplementary Cementitious Materials

Repair and restoration work of reinforced-concrete (RC) structures is increasing because of the deterioration of aging infrastructures worldwide. Generally, plain mortar and polymer-modified mortar are widely used as repair materials for RC structures. In this study the effect of the combined use of polymers with supplementary cementitious materials (SCMs) on certain mechanical and durability properties (such as compressive and flexural strengths, water absorption, carbonation, and chloride penetration) of modified mortars is evaluated experimentally. The experimental program consists of two parts. In Part I, the effect of SCM slag and silica fume (SF) on the mechanical and durability properties of mortars is evaluated. On the basis of the best performance among different slag and SF contents, Part II of the experimental program is designed, in which the combined effect of polymers and slag/SF on the mechanical and durability properties of modified mortar is evaluated. Results show that the combined slag/SF and polymer-modified mortars (PMMs) exhibited better results than polymer-modified mortar alone. Between the combined polymers and SF/slag-modified mortars, the polymer-modified mortar containing 10% SF exhibited the highest compressive and flexural strengths and the lowest chloride penetration resistance compared to those containing 40% slag. Interestingly, the combined polymer and 40% slag-modified mortars exhibited better performance in water absorption and carbonation resistance than polymer-modified mortar containing 10% SF.