Many different methods are used in order to predict the life span of a concrete structure. The test methods do not per se measure the life span of the concrete but measure the concrete's ability to prevent ingress of undesirable elements. Most of the test methods give results at 28 days which will vary depending upon the binder content, binder type, and water content in the mix. The following results are indicative and comparative of what can be expected when incorporating Super-Pozz into concrete.


Permeability

While strength development is an important criterion for concrete performance, it fails to give an insight into durability. Durability was assessed by means of a series of tests designed to measure the density and impermeability of the binder paste microstructure. Water permeability and absorption as well as chloride permeability were measured. Probably the most important consideration when using Super-Pozz, is it ability to improve the durability of concrete by decreasing the water demand without adversely affecting the workability.

Water Absorption
In this test the cubes are initially water cured for 28 days, following which cores are drilled out and oven dried for 72 hours before once again being immersed in water. The increase in mass resulting from the immersion is expressed as a percentage of the dry specimen. Higher water absorption figures are indicative of permeable concrete.

As can be seen from the results below, concrete specimens containing Super-Pozz have the lowest absorption values. This is indicative of a denser microstructure. The decrease in values from 28 to 56 days reflects an increase in density as the result of the refinement of the pore structure.


Chloride attack

Concrete exposed to marine environments is very susceptible to chloride ion ingress into the concrete which in turn corrodes the steel reinforcing. This expansion of the reinforcing causes the concrete to crack and break off. Various laboratory tests methods measure the chloride ion conductivity through a concrete specimen. Super-Pozz contains a high percentage alumina which is known to bind the chloride ions in concrete. The in-situ performance of a concrete containing Super-Pozz is therefore better than expected when comparing to the laboratory results.


Sulphate attack

Concrete exposed to aggressive soil and sewage normally fail due to the presence of sulphate in the relevant solution. The sulphate in turn forms expansive ettringite crystals causing the concrete to crack. Laboratory tests measure the overall expansion of concrete specimens submersed in MgSO3 and NaSO3 solution. These results are often used to demonstrate the resilience of a concrete exposed to these environments.

The resilience and durability of concrete containing mineral additives like fly ash is well documented and tested. It is therefore expected that concrete containing Super-Pozz to be comparatively durable.