Ayman Ababneh

Reliability analysis of chloride penetration in saturated concrete

Abstract Corrosion of reinforcement in concrete is a major durability problem of reinforced concrete structures. The corrosion is initiated by chloride penetration into the concrete, which is a diffusion-controlled process involving many complex physical and chemical mechanisms. Large random variation has shown in the corrosion damage of reinforced concrete structures, and there is a pressing need to develop a reliability analysis method for chloride penetration and for the onset of steel corrosion in concrete. In order to conduct a reliability analysis, a comprehensive material model for chloride concentration is developed and described, and some of the model parameters (water–cement ratio and curing time) are selected as random variables. By including uncertainties in the selected variables, the chloride penetration front at a point in time can be represented by a time-dependent probabilistic distribution. Similar to the concepts of supply and demand used in structural reliability analysis, the chloride penetration front at a target level (depth) with respect to time can be represented by the probability distribution of crossing the target level. A detailed description of the basic concepts and numerical examples are given. To include the effect of uncertainties of the material parameters, a recently developed Monte Carlo simulation program was used in numerical examples.

Effect of benzotriazole derivatives on the corrosion of steel in simulated concrete pore solutions

Purpose – The aim of this research was to develop corrosion protection systems for reinforced concrete structures under chloride attack. Benzotriazole (BTA) and BTA derivatives were used as corrosion protection materials for the steel.Design/methodology/approach – The effect of BTA and four other BTA derivatives on the corrosion resistance of steel in simulated concrete pore (SCP) solutions was studied. BTA derivatives were used as two separate protection systems: inhibition and pickling protection systems. The experiments were performed in SCP solutions which simulated concrete with and without severe chloride attacks. Electrochemical techniques, i.e. potentiodynamic polarization and electrochemical impedance, and Fourier transform infrared spectroscopy (FTIR) were used to assess the steel corrosion protection systems.Findings – The potentiodynamic polarization studies showed an increase in the pitting potential for all protection systems tested. In addition, a large increase in the steel solution interf...

Effectiveness of Benzotriazole as Corrosion Protection Material for Steel Reinforcement in Concrete

This paper presents results of an experimental investigation on the effectiveness of benzotriazole (BTA) as anticorrosion material for steel reinforcement in concrete structures. BTA is used in three different corrosion-protection systems: BTA inhibition, BTA coating, and BTA as a hybrid system. Reinforced concrete beams were cast, exposed to a 3% sodium chloride solution, and subjected to drying and wetting cycles to accelerate the corrosion attack. Electrochemical measurement techniques were used to evaluate the corrosion behavior of reinforcement. These measurements include macrocell corrosion current, linear polarization resistance (LPR), corrosion potential (Ecorr), and electrochemical impedance spectroscopy (EIS). Chloride penetration profiles for the concrete cover and visual inspection of the reinforcing steel bars were also obtained. The results show that a BTA-steel complex film was formed on the steel bar. This film improves the corrosion resistance of the reinforcing steel. Second, the applica...

Influence of synthetic fibers on the shear behavior of lightweight concrete beams

Incorporating discontinuous structural synthetic fibers in general enhances the performance of concrete and increases its durability by minimizing its potential to cracking and providing crack arresting mechanism. Synthetic fibers are non-corrosive, alkali resistant, simple to apply, and added in small quantities due to their low density; thus, a substantial number of uniformly distributed fibers are added. In this research, an experimental program was undertaken to investigate the shear behavior of lightweight concrete beams containing discontinuous structural synthetic fibers. The studied parameters include fiber content and shear reinforcement. The tests were conducted under four-point loading in a simply supported span of 0.85 m. The beams were divided into three groups based on shear reinforcement. Group 1 was designed without shear reinforcement, Group 2 with closed vertical stirrups placed at d/4 spacing (where d is the effective depth), and Group 3 with closed vertical stirrups placed at d/2 spacing. Each group contains four identical specimens except in terms of the fiber content: 0, 3, 5, and 7 kg/m3 equivalent to fiber volume fractions of 0%, 0.33%, 0.55%, and 0.77%, respectively. The experimental results showed that the discontinuous structural synthetic fibers improve the ultimate shear strength, ductility, stiffness, and toughness of lightweight concrete beams significantly. Therefore, design codes are encouraged to consider their contribution to shear strength and revise the maximum stirrups spacing when discontinuous structural synthetic fibers are used. The results also showed that addition of discontinuous structural synthetic fibers reduces the crack width of lightweight reinforced concrete beams. The effectiveness of the discontinuous structural synthetic fibers decreases as the stirrups spacing decreases.

Transverse cracking of composite bridge decks

Early age cracking of concrete bridge deck is a frequent problem for bridges worldwide. This work provides a framework for a thermo-hygro-mechanical mathematical model for the analysis of early age transverse cracking of the bridge deck. The model includes the determination of the temperature and moisture gradients in the deck slab, and the prediction of the thermal and drying shrinkage strains. These strains were superimposed with the strains from creep and mechanical loads and applied to an elasto-plastic damage approach to quantify the damage and stresses in deck slab. The model was implemented in finite element computer software to accurately predict the cracking and damage evolution in concrete bridge decks. Accurate prediction of crack tendency is essential for durability design of bridge decks, thus more sustainable bridges with increased usable life span and low life-cycle costs.

RECYCLING OF WASTE GLASS IN MORTAR MIXTURES

There is a growing environmental concern in many countries around the world from the accumulation of solid waste glass since not all glass can be recycled into new glass. This study explores the recycling of solid waste glass in concrete mixtures to reduce the environmental pollution and to improve the properties of concrete material. Three waste glass powder (WGP) levels were considered in this study: 5%, 10% and 15%. The properties investigated include: setting time, workability, compressive and flexural strength and micro-structure of mortar. The mortar mixtures proportions were 1:3:0.7 by weight for cement, sand and water, respectively. The results showed that the solid waste glass can be recycled in cement concrete mixtures and improve the properties of concrete. The setting time of cement paste increased and the workability decreased with the increase of the WGP content. The compressive strength of mortar increased with the increase of WGP as partial replacement of limestone sand under moist curing. The flexural strength of mortar increased with the increase of WGP as partial replacement of cement or sand under moist curing. The autoclaved WGP mortar showed higher compressive strength and lower flexural strength compared to the moist cured mortar. The scanning electron microscopy images showed that WGP material is good filler because it reduced the porosity of mortar.