The former is predicated on some and combinations of the following methods in determining the conditions of reinforced concretes i visual inspections of surface and under carriage of concrete structures; ii delamination survey with the use of steel hammer or rod in sounding the structure.
Although a destructive analogue of holes drilling to make direct measurements have been employed as well, however, the former is preferred for obvious reasons; iv determination of chloride content with the aid of ion specific probes.
Such probes convert voltage measurements from a solution of 3 grams of concrete powder taken at a specific depth, into percent chloride by weight of concrete; v Others include potential mapping as per ASTM C standard; petrographic analysis; determination of rebar cross section loss; rebound tests using a spring driven hammer and penetration test which involves driving a small rod into the concrete while the distance of penetration indicates the compressive strength of the concrete.
Thus, models developed along these routes do not take into consideration the time and other environmental-dependant corrosion damages to the rebar which influence the integrity of the concrete in service. The corrosion rate dependent models have been developed by various researchers, however, the most popular is that developed by Weyers et al. To this period, it was stipulated that years are added for the corrosion products of the steel to build up to an extent that will cause extensive damage to the concrete in order to warrant damage control management.
Prior to discussion on damage control management, it is pertinent to mention methods for corrosion monitoring techniques for rebar corrosion in order to forestall end of service life maintenance.
Others are monitoring by polarization resistance probe method and monitoring by alternating current AC impedance which may still in its infancy for use on steel in concretes. It has the advantage of being independent of the resistivity of the concrete.
This was confirmed to be true during visual inspection which revealed little or no corrosion of the steel after the reinforced bridge was loaded to failure. Other corrosion and environment-induced concrete damage monitoring methods, such as imaging techniques have been advocated by various researchers [13,14], however, evaluation of relevant and promising processing technologies are still ongoing. It is common knowledge that, C-steel reinforcements require rehabilitation and maintenance within years of construction.
Apply corrosion inhibitors on all surfaces and in case of delamination, add corrosion inhibitors to repair mortar. There are various types of inhibitors [16], some synthetic [17] while others are naturally occurring and can be extracted from several plants such as pawpaw leaves [18] and the dried skin of onions which has no food nor commercial value but its extracts performed well as corrosion inhibitors [17] cannabis extract [20], argan extract [21], onion extracts [22], coriandrum sativum leaves extract [23], veronica amygdalina [24,25], Jatropha curcas [26], curcuma longa [27], rice husk [28, 29], treculiaafricana [30], atropa belladonna [31] and many more.
These are eco-friendly and sustainable. However as mentioned by Oki [32] elsewhere, the biodegradability of green inhibitors puts them at a disadvantage because microbes will feed on them and their dosages will be continuously replenished in order to maintain a reasonable level of corrosion control which may imply higher costs. In addition microbial induced corrosion may become very important in such an environment after a protracted period of time. Another important rehabilitation strategy is the use of cathodic protection.
Although this can be incorporated at the design stage, it is also useful in arresting the advancement of rebar corrosion in on-going reinforced structures. When applied at later stages of commencement of chloride induced corrosion, the alternate anodic reaction will be the oxidation of chloride leading to formation and elimination of chlorine as gas from the environment of the concrete with limited moisture content [33].
There is a web based tool described by Broomfield [34] in which the technique selects repair options and analyze life cycle costing of corrosion damaged rebar concrete structures. From such considerations, it was concluded that from quantitative analyses of good quality survey data, the costs and advantages of different repair options can be obtained objectively.
Conclusions For reinforced agricultural facilities, it is best to incorporate, at the design stage, corrosion prevention gadgets such as means of monitoring corrosion of rebar and cathodic protection, use of inhibitors in concrete, as well as planned maintenance schedule. Prediction models are veritable tools in the management of rebar corrosion. However, management of reinforcement bar corrosion and its attendant damage to concretes should commence at design stages wherein all relevant and necessary corrosion prevention methods and monitoring techniques are incorporated.
Effects of cost-effective alkaline additives on the hydration of slag-cement mixtures, J. Influence of curing conditions on the mechanical and physical properties of chemically activated phosphorous slag cement, Powder Technology, , Influence of applied loads on the permeability behaviour of ultra-high performance concrete with steel fibers, Journal Applied concrete Tech, 14, Utilisation of phosphorous slag and fly ash for the preparation of ready mixed mortar.
Applied Mechanics and Materials, , Comparison of different methods for activation of ordinary Portland cement-slag mortars, Construction and Building Materials, 25 1 National Association of Corrosion Engineering, Houston. Corrosion Resistance of Concrete Reinforcement. This book contains not only all the important aspects in the field of corrosion of steel reinforced concrete but also discusses new topics and future trends.
Part One of the book tackles theoretical concepts of corrosion of steel in concrete structures. The second part moves on to analyse the variety of reinforcing materials and concrete, including stainless steel and galvanized steel.
Part Three covers measurements and evaluations, such as electrochemical techniques and acoustic emission. Part Four reviews protection and maintenance methods, whilst the final section analyses modelling, latest developments and future trends in the field. The book is essential reading for researchers, practitioners and engineers who are involved in materials characterisation and corrosion of steel in concrete structures.
Corrosion Rates of Steel in Concrete. A large number of ocean and harbor concrete structures have been in service for more than a century. However, the cost associated with repair of these structures damaged by corrosion of steel in concrete is a major maintenance expense for the owners.
Due to wave and tidal action of sea. The most frequently used stainless steels are examined together with an analysis of their reinforcement properties. Special attention is given to their handling and their welding requirements and the economics of their use.
A comprehensive overview of surface treatments and corrosion inhibitors is presented alongside their practical applications as well as detailed coverage of electrochemical protection and maintenance techniques. Corrosion in reinforced concrete: processes and mechanisms.
Monitoring of corrosion in reinforced concrete structures.
0コメント