New grout mix bolsters PT specialist’s competitive edge

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VSL Construction Solutions a leading South African post-tensioning (PT) contractor has introduced a new grout mix for its bonded PT systems used in building and civil structures.

Paul Heymans, General Manager of VSL Construction Solutions, says that the new grout mix is in line with the company’s focus on constantly innovating to improve the performance of its PT technologies.

“Grout is a vital component of any bonded PT system. It serves a dual purpose in that it protects the PT strands against corrosion to ensure the durability of the PT tendons and also serves as a bond between the tendon and the surrounding concrete. The consistently high performance of the new grout mix will provide us with increased confidence we need on all our construction sites,” Heymans says.

The new grout mix has already been approved by engineers and, as a result, been introduced on all of the company’s projects.

PT Grout is blended by Epoxerite Products

PT Grout is blended by Epoxerite Products, a leading construction chemicals specialist, at its sophisticated plant in Westonaria, Gauteng.

George Weideman, Managing Member of Epoxerite, designed the new concept grout in association with VSL and also participated in the testing of the new grout mix to ensure it meets VSL Construction Solutions’ very high performance standards.

Eight different grout mixes were tested at Contest Concrete Technology’s laboratory in Durban, KwaZulu-Natal, to COLTO and EN445/447 standards.

Various grout mixes were first tested for fluidity and compressive strength. Those that displayed the best flow results during flow cone testing and consistency based on visual assessments were then also tested for bleed and shrinkage using the Wick-induced test.

The Wick-induced test was undertaken to EN445/447 requirements, which is a more onerous test method than the COLTO specified test.

As the COLTO specification does not specify a shrinkage limit in grout, the EN standards were used as a guide as it establishes clear acceptance criteria for shrinkage at -1% and expansion at +5%.

Notably, the three samples were well within the limits set by COLTO and on the limit established by EN447 for bleed (0,3% versus 2% specified by COLTO and 0,3% specified by EN447) and shrinkage (0,6% average versus 1% specified by EN447).

The results of the testing revealed extremely good fluidity traits which, importantly, did not deteriorate significantly within 30 minutes from initial mixing. This provides an extended work-ability window for pumping without affecting compressive strength after 24 hours.

Although fluidity testing was mainly undertaken according to T(0) and T(30), the mix demonstrated sound work ability of up to an hour when agitated constantly.

The compressive strength far exceeded the acceptance criteria set by COLTO and EN447 within 24 hours in all related tests. This is believed to be as a result of the high quality of VSL CEM1 grade 52,5N cement that is used as the primary ingredient in the grout mix.

VSL PT Grout is packaged in 25kg VSL pockets that are both safer and easier to handle by the company’s skilled and experienced grouting teams on project sites.

Performance of the grout needs to be predictive and consistent in all weather conditions

Notably, the new grout also consists of Epoxerite’s PT-Flow additive. ”We undertook numerous consultations with VSL and visited many of the company’s sites. Importantly, the performance of the grout needed to be predictive and consistent in all weather conditions. Notably, Epoxerite PT Flow grout managed to also out perform all of the specifications, while being more cost effective than those used previously by VSL. Further savings were also recorded through declining stock shortages and reduced strain on equipment,” Weideman says.

Heymans lauds the Epoxerite team for its stellar effort and willingness to assist VSL Construction Solutions develops and tests the new grout mix.

“Epoxerite continues to provide a quality service to VSL Construction Solutions by undertaking regular testing of the materials and additives used in our grout mix. This has ensured a regular supply of high-quality grout and additives that we need to provide a cutting-edge service to our contracting clients,” he says.

This leading construction chemicals specialist also supplies tailored solutions to other prominent participants in the civil, construction and mining industries.

“Products are tailored to the clients’ requirements and specifications, and then packaged under private labels. VSL Construction Solutions is a demanding client considering the complex nature of its projects. The consistently high performance of its grout in these applications is testament to the high level of service that we provide our clients in the construction industry,” Weideman concludes.