B. Martín-Pérez

A study of the effect of chloride binding on service life predictions

One of the major causes of deterioration of reinforced concrete structures is chloride-induced corrosion of the reinforcing steel. The magnitude of the damage is especially large in structures exposed to marine environments and de-icing salts. The capacity of the concrete cementitious system to bind chloride ions has an important effect on the rate of chloride ionic transport in concrete and on the corrosion initiation of the steel reinforcement. This paper reviews mathematical models used in the literature to describe chloride binding in concrete. The impact of the different binding relations on the time-dependent chloride penetration profiles is investigated by solving the chloride mass conservation statement with a finite-difference approach. Results are presented for a concrete structure subjected to two different exposure conditions: submerged in seawater and exposed to de-icing salts. The implication of accounting for chloride binding in service life estimations is discussed.

Numerical solution of mass transport equations in concrete structures

Abstract To calculate the service life of reinforced concrete (RC) structures, the process of reinforcement corrosion was modeled using a numerical formulation of the associated mass transport partial differential equations. Migration of chlorides, moisture and heat transfer within concrete, resulting from seasonal variations in the surface conditions of the RC member, form a coupled boundary-value problem, which was solved in space using a finite element formulation and in time using a finite difference marching scheme. The stage of active corrosion was modeled by including in the numerical algorithm of the FE formulation the mass conservation equation that describes diffusion of oxygen in the concrete cover. The paper presents details of the FE formulation and computed results from selected case studies.

Detection of cracks in a reinforced concrete beam using distributed Brillouin fibre sensors

This paper presents the results of using distributed Brillouin fibre sensors to detect crack formation in a simply supported reinforced concrete beam subjected to four-point loading. A Brillouin multiple-peak fitting method was used to enhance the spatial and strain resolutions of the measurements. By doing this, the distributed strain profile along the beam was determined with a 5 cm read-out resolution in comparison with the 15 cm spatial resolution of the fibres. The location of the cracks was identified by locating the positions in the strain profile where the strain suddenly changes, by searching for the maximum compressive or tensile peaks in the Brillouin frequency spectrum, as opposed to conventional strain reading, which focuses solely on the maximum Brillouin peak. The amplitude of the Brillouin peak for the suddenly changed strain (crack) was found to be smaller than half of the amplitude of the maximum Brillouin peak at the maximum strain location corresponding to the average strain of the material, which would have been neglected by standard peak or area fitting methods, especially for fine cracks or the initial crack build-up period.

Strain monitoring in a reinforced concrete slab sustaining service loads by distributed Brillouin fibre optic sensors

Reinforced concrete (RC) structures deteriorate and as a result crack due to extreme loading and (or) environmental conditions. Damage accumulation as such adversely affects the structure’s durability properties, impairing its service life. The intensity of cracking in an RC structure is usually regarded as the key criterion toward damage assessment and repair intervention. This paper presents the results of an experimental program in which the concrete strains of a small-scale RC slab sustaining in-service loads were monitored by traditional electrical strain gauges and distributed Brillouin fibre optic sensors in an attempt to detect damage due to crack formation. A comparison of these measurements with classical bending theory is also presented. The results show that distributed Brillouin fibre optic sensors can capture both tensile and compressive strains in concrete; however, the accuracy of their measurements is dependent on the proper installation of the sensors and the fibre length over which the ...

Wind Resistance Correlation of Adhesive Applied Roofing System

The adhesive applied roofing system (AARS) is a new generation of built-up roof, gaining popularity in the Canadian low-slope roofing market. All components of the AARS are integrated using adhesive and unlike mechanically attached roofing systems, there are no fasteners used. Thus, an AARS can offer less thermal bridging, air intrusion, air leakage, moisture migration, and corrosion problems. The components are, however, subjected to the combined action of tensile and shearing forces due to the dynamic wind uplift action as a result of wind flow suction over a low-slope roof. As part of an ongoing collaboration between industries, universities, and government departments to quantify the wind uplift resistance standards of the AARS, three different testing methods have been successfully developed: (1) uplift resistance testing, (2) peel resistance testing, and (3) wind uplift testing. Small scale specimens were used for the uplift and peel resistance testing, whereas wind uplift investigations were performed using full-scale mock-ups. This paper focuses on a proposed correlation amongst these three different test methods, namely, “Higher resistance in both peel and uplift tests will result in the same or higher wind uplift resistance.” Four different scenarios of two sets of samples each were constructed by varying only one component between the samples. All samples were tested in all three tests methods and data from these tests were compared to verify the proposed correlation. The test results obtained from the small-scale experiments proved to be useful to predict full-scale system behavior as demonstrated in the paper through comparison of the resistance data and failure modes.

Stress wave propagation for evaluation of reinforced concrete structures

Abstract: Failure of service-critical systems owing to ageing and/or faulty design practices highlights the vulnerability of these systems and the need for proactive management. Structural deterioration may be attributed to ageing, extreme environments and/or inadequate investment in regular maintenance and repairs. The proactive management can be integrated during initial construction quality control, monitoring of in situ response and environmental changes (such as variation of load change and traffic volume), and during quality control of repaired structures. This chapter explores the application of stress wave propagation techniques during the life cycle of the structure to instigate proactive decision action.