Concrete admixtures are materials added to concrete before or during the mixing process, in addition to cementitious materials, aggregates, water, and fiber components. It is mainly used to improve fresh and hardened concrete performance and has no harmful effects on human, biological, or environmental safety.

Just weeks after a 900-unit apartment block was found to be in danger of collapsing, developers of yet another apartment block have been told to address a series of issues urgently.

The five-storey building at 11-15 Mitchell Ave in Jannali, in Sydney's south, which consists of 31 apartments, had 47 defects found during an inspection in 2023, developer of the new-build apartment development Mitchell Avenue Development said this week. Four received a building works rectification order from the NSW Building Commission.

The report said there were problems with the building's concrete and waterproofing, and fire safety did not comply with regulations. Mitchell Avenue Development has 120 days, by May 31, to complete work to fix the defects.

Cracks were found in the concrete of apartment balconies and the building's fire stairways, and foreign objects were found in materials in various areas of the underground car park. The fire stairway on the fourth floor of the building had cracked concrete and exposed steel bars, causing rust. Concrete in other sections was found to need to be properly vibrated or compacted.

Waterproofing issues accounted for 16 defects, as inspectors found numerous instances of water penetrating properties and damaging apartments. A further 17 defects were found to be related to fire safety, one of which included a gap found in a fire door. All cabinet doors on the residential floors were also found to be without fire-resistant, non-combustible coverings or smoke seals. The report said Mitchell Avenue Development was committed to fixing the defects, but they questioned why builder Truland Development was not held accountable.

NSW Acting Building Commissioner Elizabeth Stewart wrote in the report that the extensive work to fix the defects could be expensive but must comply with industry standards. Greenland Australia, the developer of 23 Halifax St in Macquarie Park, was issued another building works improvement order a few weeks ago.

Concrete slabs were severely damaged and deteriorating at the joints between the basement and first floor and on the 6th, 11th, 17th, 22nd, and 31st floors. The horizontal floor surfaces of the basement and roof were also deemed not to have sufficient slope to the drain openings, causing excess water to accumulate in the area. Artistry defects reportedly caused the problems and could cause the entire 900-apartment building or part of it to collapse. Planning records show the development, which has 31 apartments, was approved by Sutherland Shire Council in 2018.

There are many types of concrete admixtures, and each type has different effects.

Air-entraining agent: Air-entraining agent can introduce an appropriate amount of stable bubbles during the concrete mixing process, thereby improving the durability of the concrete. It is mainly used in projects with anti-mixing and anti-freezing requirements.

Retarder: Retarder can extend the hardening time and hydration time of the cement contained in concrete, reduce the hydration heat generated in the early stage of concrete, avoid concrete cracking, and prevent construction joints in concrete due to continuous pouring. In addition, it can also maintain good workability of concrete constructed at high temperatures and extend the release time of hydration heat to avoid surface cracks.

Early strength agent: Early strength agent can shorten the setting time of cement contained in concrete. It suits steam curing, prefabricated components, and concrete projects with low temperature and early strength requirements. It can improve the early strength of concrete, speed up construction progress, and shorten the time of concrete Construction and maintenance time.

Water-reducing agent: Water-reducing agent can reduce the amount of cement contained in concrete, has a relatively high water-reducing rate, can effectively reduce the loss of concrete slump, increase the filling and pumpability of concrete, and reduce equipment and Operational effects to maintain the stability of concrete.

In addition, other types of concrete admixtures, such as composite expansion agents, waterproofing agents, and rust inhibitors, are used for different purposes, such as improving the early strength and impermeability of concrete and preventing corrosion of steel bars.

When selecting concrete admixtures, the correct choice should be made based on the actual construction environment, construction needs, etc., to ensure the best improvement in concrete performance. At the same time, when using concrete admixtures, they need to be evenly mixed with the concrete in the correct proportion to ensure that the admixture can fully exert its effect.

Supplier

TRUNNANO is a supplier of waterproof agent(which is one of concrete additives) with over 12 years experience in nano-building energy conservation and nanotechnology development. It accepts payment via Credit Card, T/T, West Union and Paypal. Trunnano will ship the goods to customers overseas through FedEx, DHL, by air, or by sea. If you are looking for high quality concrete additives, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com).