In today’s increasingly competitive and challenging structural concrete marketplace, the need for innovative solutions to challenging forming issues is greater than ever. Shotcrete is a more logical and efficient option for structural concrete applications with the added benefits of sustainability and environmental responsibility
All vertical, two-sided formwork is designed to withstand a minimum of 2900 kg/m2 of concrete head pressure. The resulting forms are substantial and heavy to carry this high internal pressure.
With shotcrete applications, however, a one-sided form is all that is required and this form only needs to withstand 240 kg/m2 of pressure. This reduced pressure requirement is a direct result of the high velocity, pneumatic application of the concrete impacting over a small area as opposed to pouring in a form that has fluid pressure along the entire form length. There’s far less pressure at the bottom of a one-sided shotcrete form and the pressure resistance requirement is only to keep the form from moving or vibrating during the shotcrete placement.
With the dramatic decrease in form pressure, forms can be much lighter and thinner than traditional form-and-pour panels. And with the need for only a one-sided form rather than a two-sided form factored in, overall formwork materials can be reduced by up to 75%. In addition, the reduction in form pressure means that details for corners, intersections, fillers, and bulkheads are easier to produce resulting in significant material and labour savings.
The decreased volume of formwork materials required on the jobsite further reduces storage needs and crane requirements. The number of forms that must be stored offsite and transported to and from the jobsite is lessened; that also reduces costs while accelerating scheduling. By reducing the amount of formwork required and thus eliminating a substantial portion of transport requirements, a shotcrete application reduces the environmental impact of a project and contributes to more sustainable construction.
When the quantity, size, weight, and complexity of onsite formwork are reduced, labour requirements are also minimized. When labour requirements decrease, schedules accelerate. Schedule acceleration reduces site overhead, which results in less consumption and greater sustainability. From the offsite prefabrication and delivery stage right through to clean-up at the end of the project, structural shotcrete can increase sustainability and result in a more durable, longer life structure that requires less maintenance in the future. As an additional bonus, fewer deliveries means less traffic congestion. On remote sites, the reduction in transport time and lessened crane requirements also reduces project completion timing and transport costs.
With the combined savings achievable in materials, labour, and site logistics, structural shotcrete offers opportunities not available or associated with two-sided form-and-pour methodology:
Wet-mix shotcrete placement creates a fresh concrete surface that can be a trowelled to a smoothly finished surface free of lift lines, and form tie holes. The surface is denser and can be treated like an industrial floor. The result is a longer life cycle with added protection against freezing and thawing, chloride penetration, abrasion, and wear from environmental conditions. These characteristics enhance the overall sustainability of the shotcrete application methodology. Structures that last longer have less overall impact on the environment.