In my previous article, I wrote about the introduction to BS EN 1504 and the two categories of principals which involve concrete (Principal 1 to 6) and reinforcement bars (Principal 7 to 11). The followings are details about each principal for better understanding when selecting the appropriate prognosis based on analyses conducted from diagnostic procedures.

Principal 1: Protection against aggressive substance. This principals highlights the need to have proper protection against aggressive substances or substrates such as chloride from seawater, chlorine from swimming pool, gasses in factories and corrosive environment, and other chemicals from direct physical contact. Substantial cracks allow these substances to infiltrate and existing pores from high water cement ratio and hydration process will allow deeper penetration and reduce the durability of the concrete by lowering its passivity.

Principal 2: Moisture control of concrete. Concrete with high moisture content have high potential to trigger corrosion. There are different states of water (H20) which leads to a chain of redox reaction when in contact with reinforcement bar. Other detrimental substrates will aggravate the whole condition and work as catalyst(s) in my many forms in many states, as gas, liquid, aqueous, and/or hydrate (solid).

Principal 3: Replacement of damaged concrete. When concrete has lost its integrity in certain section or part of structural members, the affected section shall be replaced by newer concrete. Replacement will allow partial rejuvenation and reinstates its initial intended purpose from further degradation.

Principal 4: Strengthening of building component. Under extreme condition where concrete degradation will affect its overall performance in a larger section of master or slave structural system, strengthening is required by introducing new components through retrofitting.

Principal 5: Improvement of the physical resistance of concrete. Unlike replacement and strengthening principals, this principal is not limited to overall integrity and strength. It is a way to introduce preliminary barrier or jacket against element and physical attack/ingression and retain the durability of the concrete.

Principal 6: Improvement of Chemical Resistance. This principal have similar intention as per Principal 5 but with specific intention(s) to create or increase durability from aggressive chemical attack.

Principal 7: Restoring reinforcement passivity. Principal 7 is designed to preserve the reinforcement bars from corrosion when concrete is infiltrated by detrimental agents and lost its passivity. The introduction or enhancement of barrier such as covers and actions to re-alkalized the concrete and reinstate its cover and infill passive state.

Principal 8: Increase of the electric resistivity of concrete. Electric resistivity is a property which retards the potential for current or charges formed by anode and cathode for the same reinforcement bars or adjacent reinforcement bars.

Principal 9: Control of cathodic areas of the reinforcement. Before current flow induces the movement of electrons, this principal will take the prevention step from forming anodic reaction and reduce the potentials of corrosion of the reinforcement bars.

Principal 10: Cathodic protection of reinforcement. When corrosion occurred and yet to be extensive, methods are introduced to suppress the potential of corrosion at anodic areas of the reinforcement. This principal approved both active and passive systems.

Principal 11: Control of anodic areas of reinforcement. Another method of suppressing corrosion is by tackling the anodic area instead of cathodic areas as per Principal 9. Most of the time, a sacrificial element and/or films are introduced using material based on its range of metal nobility.

Therefore, with these principals, engineers and/or technologists can choose appropriate principal(s) and financially optimized method(s) specifically for localized defects and holistically, structural integrity. The right methodology of repair, rejuvenation and rehabilitation would enable the structure to prolong its intended lifespan.