Add 60 years to service-life of concrete in critical environments
Historically, the prime concern for concrete designers has been its resistance to mechanical stress, i.e. strength. In recent years, durability has emerged as equally important.
However, durability cannot be achieved with reducing the W/C ratio, high compressive strength, more cement, air-entraining admixtures or corrosion inhibitors alone.
To achieve concrete durability in critical environments, properties like low permeability, low shrinkage, self-healing and protection against chemical attack must be realized. PENETRON ADMIX incorporates the technology that provides such properties and recent testing has shown it can add up to 60 years or more to a variety of concretes, including CEM II /B-P, CEM II / B–S and CEM III/A, in critical environments before the onset of corrosion.
These results are in line with ACI report 212.R3-10, which concludes that crystalline admixtures are the best PRAH (permeability reducing admixtures for hydrostatic conditions) and increase durability of concrete.
Details of this durability testing are provided below.
Jozef Van Beeck Director International Sales & Marketing
In order to establish the effect of PENETRON ADMIX on the durability of concrete, a complete research project was executed at leading independent laboratories over a 2-year period. The testing included compressive strength, drying shrinkage, permeability, sulphate resistance, chloride diffusion resistance, freeze-thaw cycle resistance, self-healing ability, microscopic examination of crystalline formation and most importantly – a resulting service-life estimation of concrete treated with PENETRON ADMIX.
The results of this testing regime are summarized in the following table.
Each test result will be expanded upon in detail in these durability updates going forward – in this issue we will focus on the service-life estimation based on Chloride diffusion only.
SERVICE-LIFE ESTIMATION OF CONCRETE IN CRITICAL ENVIRONMENTS
The mechanism of concrete deterioration by chloride diffusion looks as follows.
Chloride diffusion testing performed according to ASTM C1556 yielded the following results, with and without PENETRON ADMIX.
Table 2. Apparent chloride diffusion coefficient
Initial Content Cl Ci (%)
Superficial Content Cl Cs(%)
Apparent Diffusion Coefficient Cl(m2/s)
C WITHOUT PA
C1 WITH PA
C2 WITH PA
C and C1: CEM II/B-P
C 2: CEM II / B-S
PA : PENETRON ADMIX
Using the 2nd Fick law of diffusion, we can then estimate the service-life of concrete based on the chloride diffusion coefficient and the cover of steel, obtaining the following results.
Note: testing was done under exposure conditions conforming to ASTM C1556
This testing shows that, in an environment with chloride concentrations 4.7 times higher than true marine environments, PENETRON ADMIX treated concrete can add up to 60 years and more to the service-life of a conventional concrete, before the onset of corrosion.
A second chloride migration test in accordance with Nordtest, done on an extremely durable concrete mix design CEM III/A, still yielded another 40 years of service-life extension with PENETRON ADMIX.
CASE STUDY : SINGAPORE SPORTS HUB / NEW SINGAPORE NATIONAL STADIUM
Singapore is now home to the world’s largest dome structure
The Singapore Sports Hub, built on the original site of the National Stadium, has opened its doors on June 30, 2014 and is the country’s new central sports destination.
Works on the site began in September 2010 after the demolition of the former Singapore National Stadium. The new facility includes a new 55’000 capacity National Stadium, a 3’000 capacity indoor Aquatic Centre with leisure facilities, a 3’000-capacity multi-purpose Indoor Arena, 41’000 square meters of commercial space and a Water Sports Centre on the shores of the Kallang Basin. This includes a Sports Promenade, the Singapore Sports Museum, the Sports Hub Library as well as the Kallang Wave Shopping Mall.
The Sports Hub’s centerpiece is the new Singapore National Stadium. This landmark structure is currently the world’s only multi-purpose arena with mechanized and automated retractable seating configurations on its lower tier. Within 48 hours the stadium can be reconfigured to host different events such as concerts, football and rugby matches, cricket and athletic events. The dome structure features a retractable roof, making the National Stadium an all-weather event facility.
Approved by the Singapore Environmental Council (SEC) with the Singapore Green Label, the PENETRON System was chosen to ensure the concrete durability on this iconic, green building development. PENETRON ADMIX was used on approximately 55’000 cubic meters of base slab and retaining walls. Penebar SW 55 waterstops were installed in over 18’500 meters of construction joints. In addition, 16’000 square meters of internal wet areas and exposed concrete including the RC roof were treated with Peneseal Pro.
The project is yet another milestone in PENETRON’s long-standing track record of protecting Singapore’s infrastructure.