Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633545
Title: The effect of steel bar corrosion on the bond strength of concrete manufactured with cement replacement materials
Author: Elbusaefi, Adel A.
ISNI:       0000 0004 5346 5397
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2014
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Abstract:
This thesis presents a study of the bond strength between corroded and uncorroded steel reinforcement and the surrounding concrete within steel reinforced structures. The work is based on concretes manufactured with different types of cement replacement materials, and investigates the influence of the corrosion rate of steel as predicted by concrete permeability. The cement replacement binders included CEM II, blended cements of fly ash (PFA), ground granulated blast-furnace slag (GGBS), metakaolin (MK) and silica fume (SF). The experimental work was conducted by placing 200mm cube test specimens in a saline solution (3.5% NaCl) for different exposure times (3, 7, 10, 14 and 20 days) with an applied external current of 10 mA between the reinforcing steel and a stainless steel counter electrode. Pull-out tests were conducted to evaluate the bond strength between the concrete and the steel reinforcement. The permeability coefficients of concretes were investigated using a relative gas permeability test. The specimens used for determining permeability were cylindrical 100mm diameter and 100mm length, which were oven dried at 105 ºC. The experimental results indicated that the bond strength was governed by concrete properties. Furthermore, the bond strength of the corroded specimens was found to depend on the corrosion levels and varied across all concrete types, depending on the concrete microstructure. Moreover, when the corrosion level exceeded 1.74%, the bond strength began to decline. Thereafter, the bond strength continued to reduce as the corrosion time of the reinforced concrete increased. The relationship between the compressive strength and gas permeability of concretes was inconclusive but the latter does depends on the cement replacement levels. The PFA concretes had the lowest permeability compared to the other two types of concrete (CEM II and GGBS). The permeability of concretes and corrosion rates with different types and levels of cement replacement materials significantly decreased as the age of concretes increased. The improvements in gas permeability and corrosion rate were observed when 40% of cement weight was replaced with PFA. The ABAQUS program was used to model the bond-slip behaviour of different concrete mixes, in addition to a plastic damage model. A cohesive zone element was employed for the steel-concrete interface. During analysis, the numerical model was validated against the results obtained from the experimental tests. The numerical results showed good agreement with the experimental results for CEM II, GGBS and SF concrete specimens, but in the case of PFA concrete where the numerical result of bond strength was overestimated by to the experimental ones.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.633545  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General)
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