Enhancing Resiliency with Rapid Set Cement

Rapid Set cement offers design and construction professionals a chance to work with a concrete mixture that exhibits minimal shrinkage and sets quickly, reaching 30MPa Compressive Strength in around one to two hours pending ambient conditions. While it may be a different binder to traditional binders (Portland based cements), Rapid Set has its own long history of success internationally and locally on major roads/Motorways, International Airports and many more civil construction projects. 

The key to using Rapid Set to best effect is to learn how to take advantage of and control its unique properties when carrying out repairs on infrastructure that can be returned to service within hours, exhibiting near-zero shrinkage and durability. Concrete made with Rapid Set Cement is not a miracle – it is a carefully engineered material science that simply requires some basic skills and knowledge in order to be used effectively.

Rapid Set cement has been around since 1975. The hydration reaction of Rapid Set Cement is such that all free water in the mix is consumed at a very early stage through the early creation of ettringite crystals. The concrete does not bleed and has much smaller pores and capillaries than those created by rising bleed water in traditional concretes. The result is lower permeability and very low drying shrinkage making a long lasting, durable concrete.

The most commonly raised question regarding Rapid Set Cement is about the cost. However, the cost of a premium product is generally offset by time savings – often vital in projects that require rapid return to service and a durable repair. Overall, time is much more costly in the scope of such projects than the initial outlay for Rapid Set Cement. 

For first-time users, there can be concerns about less working time associated with rapid-setting concrete mixes. While this can be a big issue with other fast-setting traditional cement-based systems, the setting time of Rapid Set Concrete can be easily controlled with commercial concrete admixtures. Most Rapid Set Concrete mixes have been designed to have about 10 to 20 minutes of working time, however, this can be easily extended to 30 to 45 minutes or longer with the addition of commercial concrete admixtures. 

• Rapid Set rapid setting products are available in a variety of formulations, including: 
• Rapid Set cement premixed with sand and aggregate to produce a Rapid Setting Concrete Mix enabling repairs to all general concrete structures. Available in 25kg bags
• Repair mortars. Rapid Set cement and sand premixed in bags to produce Rapid Setting Mortar Mixes enabling repairs to all general concrete structures including small cracks and overhead repairs. Available in 25kg bags
• Rapid Set Concrete Mixes produced with Volumetric Mixers (Rapid Set Cement, sand & Aggregate) for large scale projects including major infrastructure works on roads and airports.

When using premixed Rapid Set Cement bagged products, surface preparation for repairs is generally identical to that for any concrete repair and just as essential for success. All damaged concrete must be removed, the matrix must be free of contaminants and dust, and reinforcing steel must be free of rust. If additional steel is needed to replace steel that has lost too much cross-section or if dowels are to be used, those need to be in position prior to starting the work. The installation process is similar to that of regular concrete, apart from the shorter working time. Portable drum mixers or drill-mounted paddle mixers can be used on smaller jobs, with mixing taking between one and three minutes. It is important as with all concrete products to follow the manufacturers guidelines.

On large scale and major infrastructure projects, Rapid Set Concrete is produced using volumetric mixers to ensure supply continuity and Quality can be provided. The Rapid Set Concrete mix is specifically designed and tested to ensure adequate working time is allowed for and specification requirements are fulfilled. Full Laboratories can be set up on site or local providers utilised for testing. Installation methods are similar to that of large-scale traditional cement concrete projects utilising as a minimum the same concreting tools. Training is available to ensure the correct equipment and procedures are 

Safety is as important with Rapid Set Cement and concrete as any other cementitious materials. Use of Personal Protective Equipment (PPE) is essential. Safe Work Australia states that WHS regulations recommend respiratory equipment with a minimum of a P2 efficiency half-face respirator and work clothing that does not collect dust be used. In all cases refer to the product Safety Data Sheets (SDS) and manufacturers recommendations when using the products.

Disaster-resilient structures continue to gain recognition around the world as natural hazards, including cyclones, storms, earthquakes and bushfires increase in number and severity. A concrete structure’s ability to withstand these natural disasters is multi-faceted and relies on adopting and implementing stringent building standards, codes and disaster-resilient engineering practices, all of which must be supported by high-quality, durable materials. 

Rapid Set Cement concrete with the correct design criteria and proven testing against specifications can meet the demanding performance requirements of disaster-resilient structures. Rapid Set Cement provides more durable concrete with improved life expectancy of the pavements or repairs carried out.

When used in emergency repair materials, Rapid Set Concrete helps improve safety on-site by reaching full strength quickly and maintaining it for the life of the placement. Rapid return to service in one to three hours helps minimise exposure to unsafe conditions for construction teams, emergency services, commuters and pedestrians and contributes to a more efficient recovery.