Tilt-Up Concrete

A technology for building construction includes numerous processes performed on the construction site. The variety of design solutions for multistory buildings are based on the use of various methods and techniques for the construction of objects that reduce terms of construction, improve the quality and reliability of buildings and structures. Such factors as design solutions, dimensions, weight of mounted elements, as well as size of the construction site or tightness of the construction site significantly affect the choice of method of the construction of prefabricated buildings. The choice of method of the building construction depends on its design and technological features, the degree of elements integration, materials of construction, means of mechanization and other factors. Methods of structural elements installation are in the direct proportion to the degree of integration of the mounting elements, sequence assembly of prefabricated elements, methods of installation of structures in the design position, means of verification, and temporary fastening of elements and other features. Nowadays, tilt-up technology gains more and more popularity. The paper will discuss advantages of the tilt-up technology, as it is a way for creation of energy efficient buildings.

The Main Principles of the Construction

The tilt-up technology is a technology for building walls by concrete fragments of walls to full height on a building site in a horizontal position and the subsequent mounting in the design position by a crane. “Tilt up wall construction is a precast construction method in which the wall panels are cast on the job site” (Wakita & Linde, 2003, p. 153). By means of special parts from foam plastic, parts of the walls are formed on the flat surface. Then, reinforcement is made, fitting pieces are placed, and concrete is laid. After concrete is solid, mounting of the walls construction is performed with the help of the crane. At the same time, the foam elements form a part of the wall, namely its outer surface, and serve as heat insulation. Thus, there is a hard monolithic frame of the future house with the insulating layer made of foam.

Building of constructions with the tilt-up method is performed with the help of wall panels. “Tilt up construction is a method using performed wall panels, which are lifted into space” (Jefferis & Madsen, 2005, p. 860). This method is used for the designs or structures assembled in a horizontal position, typically at a ground level. The rise of structures in the horizontal position is implemented by turning around a fixed pivot with the help of portals, masts with pulley blocks, and winches, using mobile cranes. The task of all mounting devices and means is to provide a smooth lifting and turning of the mounted structure from a horizontal to a vertical position. To ensure the stability of the structure during the rise, especially in the final moment of installation in a vertical position, builders use the brake winches and other devices, taking inertial power from the movement of a lifted system, sustaining the lateral wind forces and other loads that appear during lifting.

The tilt-up method is recommended to be used at the facilities ranging from 465 to 140.000 square meters. In the US, several organizations are involved in the issues of technical support of the method and produce a variety of recommendations for the design and mounting of the structure. Until recently, it was believed that the tilt-up method is economical for buildings of over 1858 square meters. However, currently, in the US, there is a growth in the market demand for the construction of buildings ranging from 690 to 929 square meters (Hurd, 2005). The wall structures made with the tilt-up method are competitive with the wall structures of the blocks or bricks that are normally used for medium-size buildings. The main economy in this case is achieved due to the absence of scaffoldings that are not needed in the method of tilt up. The cost of the construction, according to the height and area of ​​buildings, is reduced by one-third of the total by saving time and materials. At the beginning of 1980, in the US and Canada, the tilt-up method for the construction of complex objects began to be extremely widespread.

The Canadian firm from Vancouver built a two-story building of a shopping center in the city of Kamloops (British Columbia). The building with a total area of the retail space of 48.300 square meters was built in 15 months. Supporting large reinforced concrete panels were set between buttresses, necessary due to the height difference of the construction site. The height of most panels on two floors is 11.6 meters. Thickness in the first floor level is 285 mm, and in the second level – 140 mm. The maximum size of the panels used is 18 meters, weight – 36 tons. Similar panels were used for the fire protection of a building. “The concrete columns provide favorable fire protection” (Nawy, 2008, p. 28). Other major structural elements of the building include prefabricated concrete slabs, concrete and steel columns, and steel latticed roof trusses with steel corrugated sheeting covering. At the same time, the method has become increasingly popular for the construction of residential buildings (Nawy, 2008).

Advantages

One of the most important advantages of this method is maximum mechanization of work. “Tilt up concrete construction is a fast and economical method” (Ramsey & Sleeper, 2011, p. 34). Concrete is applied to the lower level. Its lifting is implemented with the crane. It is cheaper than to do it with the help of concrete pumps. Concrete placement is more technological than in the vertical formwork. “The main advantage of this type of construction is the elimination of the vertical foamwork for the walls” (Hurd, 2005, p. 21). With small dimensions peculiar to the cottage construction, there is a light and stiff frame. Hence, the condition of rigidity from the foundation can be removed. The combination of these factors makes the cost of construction comparatively cheap.

Constructions erected by the tilt-up method were not always able to compete with conventional precast concrete slabs. However, nowadays, producing firms began to manufacture panels in this system both in the factories and in the conditions of the construction site. The quality of the front trim of panels in both cases is the same. Such factors as distance from the plant, weather conditions during the construction, building time, access to the roads, and the dimensions of the panels affect the choice of the production type.

The use of the tilt-up technology in factory conditions helps reduce the production area, as well as combine the manufacturing process with the process of storage. Thus, the cost of production of panels in factory conditions according to the tilt-up technology is significantly lower than the cost of production with the conventional technology. The key to the reduction of production cost is the low cost of aluminum formworks. They do not require racks, mixers, and other technical equipment, which is characteristic for the traditional production of panels. There are also some disadvantages of this method. First of all, there should be space on the construction site to maneuver a crane. Also, there are difficult layouts of opening and reinforcing patterns. One more disadvantage of the given method is that it is extremely dangerous. Safety measures should be very strict, as heavy panels are lifted by the crane. In some cases, connections between panels look bulky. Therefore, there are more advantages than disadvantages of this method.

Energy Efficiency of the Method

Year by year, in the world economy, much attention is paid to the Earth’s resources, which were once considered inexhaustible, and nowadays, the impossibility of further uncontrolled consumption is realized. In connection with this, people try to find solutions to the economic use of natural resources. In the construction industry in many countries, more stringent regulations on energy saving and thermal insulation of buildings are adopted. There are changes in building codes for energy efficiency, which require designers to provide solutions for the reduction of future costs for lighting, heating, ventilation, and air-conditioning through the choice of appropriate technologies and materials for the construction of buildings. New regulations require a more efficient thermal insulation of structures. The easiest way is to increase the thickness of the insulating layer of heat insulation materials.

However, there are also other ways to achieve the energy efficiency of buildings – the new technologies of their construction and design. In recent years, among a large variety of technological solutions, the tilt-up method became very popular. This method is the assembly of large-sized buildings, made of the reinforced concrete panels manufactured at the site of installation, and raised in the design position by turning relatively to the lower edge. This technology prevents walls from the heat loss in the buildings, and improves the insulating properties of walls, using the panels like “sandwich”, in which the insulating layer can be applied both during the fabrication of construction, and on the finished walls. Monolithic lightproof tilt-up panels with an average thickness of 175 mm have other properties that lead to the energy efficiency of the construction. Massive tilt-up panels have the ability to store and give heat. Researchers give the examples of thermographic heat loss through the tilt-up panels and conventional prefabricated panels. The results clearly show a decrease of heat loss in the buildings constructed by the tilt-up method. In such buildings, increase of heat loss occurs only through non-insulated doors and windows. Large dimensions of the panels lead to the reduction in the number of seams, which can be a potentially weak point in the building. In addition, the tilt-up technology is able to withstand the exact dimensions of the panels, and the gap between them does not exceed 15 mm.

This method became very popular in the US, Canada, Australia, New Zealand, and South Africa. Recently, in the US, a building was built with the help of the tilt-up method in Austin, Texas, and the Office of Environmental Protection has assigned it to the category of buildings “Energy Star”. The building consumes up to 40% less energy than conventional comparable buildings. Large panels provide an internal space of the house with opening windows at each end of the house, creating natural ventilation and reducing the cost of air conditioning. Concrete panels increase the energy efficiency of the building. Nowadays, the world’s largest structure built with the tilt-up method is a warehouse building in South Africa. The building with an area of ​​3.1 million square meters was built in 1.5 years. Such a quick construction time became ​​possible due to the tilt-up method (Nawy, 2008).

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Conclusion

It is impossible to list all the details of mounting works and all the techniques used by construction companies. The designed solution will bring significant cost savings and material resources, as well as ensure the implementation of work on time and with high quality. In many countries of the world, in the modern construction of buildings of low and medium numbers of floors, the dominant value is taken by the technology of the construction of prefabricated panel walls using the tilt-up method. A characteristic feature of this technology is the manufacture of reinforced concrete wall panels in a horizontal position on the construction site, followed by a rotation in vertical (project) position. Until recently, this technology has been used primarily for the construction of commercial buildings and industrial applications. Currently, however, it is gaining recognition in the sphere of building construction in the housing sector. The main reason for the growing popularity of this technology is its efficiency.