Commercial concrete can be broadly defined as concrete used to build or enhance business facilities, such as industrial buildings, warehouses, retail stores, car parks and office buildings. Commercial concrete can be found nearly everywhere in a building, including the walls, floors, exterior walkways and pavements, and even the architectural details. When compared with residential concrete, commercial concrete usually has greater demands placed on it in terms of structural performance and durability.
The construction of concrete commercial buildings takes a number of forms and options.
There are a number of solutions outlined below which will vary between the requirements of each building or project:
- Flat slabs are slabs that are supported directly on columns without any beams. These slabs will be supported by cast in-situ or precast columns and in-situ walls. They are highly versatile elements widely used in construction, providing minimum depth, fast construction and allowing flexible column grids.
- Post-tensioning flat slabs is a method of prestressing that offers the thinnest slab type as concrete is worked to its strengths, mostly being kept in compression. Longer spans can be achieved due to prestress, which can be used to control deflections.
For very long span situations (greater than 12m) a post-tensioned band beam offers a economic solution. Band beams are shallow, wide beams that minimise the overall structural depth. The pre-stressing maximises the performance of the concrete and controls deflection. Typically the beam depth is 550mm to 600mm deep.
- Double-tee floor units are ribbed precast prestressed concrete units. They can be produced in a variety of depths from 200mm to 500mm. The connecting slab is approximately 2400mm wide x 50mm thick. Double Tees are ideally suited for larger spanning floors with a wide variety of services suspended from the flooring.
- Hollowcore is a 1200mm wide extruded, prestressed, voided slab unit with a reinforced concrete topping. They derive their name from the voids or cores which run through the unit, which reduce the self-weight of the slabs, maximising structural efficiency. Standard unit depths are 200, 300 and 400mm. Hollowcore is ideally suited for large floor spans with commercial loading.
- Hybrid concrete construction (HCC) makes use of precast and in-situ concrete together, combining the benefits of both to give a robust, durable construction which is fast on site with an excellent finish. There are many different forms of HCC but a popular option for commercial buildings is to use hollowcore units which are prestressed to maximise the floor span.
- Tilt-Up construction is an extremely popular method of construction to essentially put together the outside frame of a building. This is due in part to the economics of Tilt-Up, which combine reasonable cost with low maintenance, durability, speed of construction, and minimal capital investment. Tilt-up panels are cast horizontally on-site then tilted into position. The method allows pre-fabricated steel plates with lugs to be cast into the panel which allow attachment to footing, other panels, or the roof system.
It is popular to impart a pattern or texture to the face of Tilt-Up panels and the external cladding can be cast in the same process for maximum efficiency.
As well as providing the structural frame, concrete can be used to improve the overall performance of a building.
Reducing the number of columns to increase open plan areas and increase flexibility for re-use are often important in commercial buildings. The use of High Strength concrete can reduce the number and thickness of supporting columns creating more useable space. The use of a post-tensioning design is a tried and tested method that can deliver these longer spans and create more useable space.
Thermal mass is a term that describes the ability of a material to store heat; something many construction materials can do to a greater or lesser extent. But, to be useful in the built environment, they must also be able to absorb and release heat at a rate roughly in step with a building’s daily heating and cooling cycle. Concrete and masonry products do this well and, being dense materials, can also store a lot of heat. Timber absorbs heat too slowly to offer much effective thermal mass, and steel conducts heat too rapidly to be in synch with a building’s natural heat flows over the day. It therefore makes sense to choose a material that reduces the requirement for energy intensive, high maintenance air-conditioning.
Concrete can offer excellent fire resistance, well beyond most requirements stipulated by Building Regulations. This level of resistance is welcomed by fire fighters who often have to enter burning buildings. It is also welcomed by the building occupier who will want to repair the damage and return to business-as-usual as quickly as possible after a fire, rather than have the premises closed, then demolished and rebuilt.
Concrete structures provide an airtight building with minimum air leakage from interface and joint detailing. A high rate of air leakage can account for significant heat loss from a building. Reducing air leakage will reduce the ongoing operational costs of heating and cooling.
Some building designs will require a minimum noise transmission between rooms and floors. Concrete’s inherent acoustic performance provides excellent sound insulation.
Security is a major consideration for commercial buildings. Concrete walls offer greater resistance to unlawful entry such as ram-raiding and prevents the opportunity for thieves to cut through lightweight steel warehouse walls. In addition, robust concrete walls offer greater resistance to the impact damage that is often caused by fork-lift trucks.
Markets and working practices are constantly changing, therefore it makes sense to consider a material that can accommodate changing needs or be adapted with minimum effort. A concrete frame can easily be adapted to other uses. Holes can be cut through slabs and walls relatively simply, while there are methods to strengthen the frame if required.
Commercial and Industrial Floors
Commercial and industrial concrete floors and pavements often require a higher strength or durability to perform in the application required. This could be for abrasion resistance of the surface or the type of environment the concrete is subjected to. The inclusion of Microsilica 600 at an 8% replacement will provide the concrete floor with higher abrasion resistance, increased inherent strength and improved resistance to chemical and acid attack.
There are a number of different design options available in addition to conventional reinforced concrete floors such as post tensioning or steel fibre reinforced. With consultation of a qualified design engineer, Steel fibres can either work with conventional reinforcement to give tighter crack control and enhanced durability or they can completely replace reinforcement to provide slabs that are not only easier and faster to construct, but offer enhanced performance in terms of load carrying capacity, impact resistance and fatigue performance.
Commercial floors also need high-performance finishes or coatings that are appropriate for the application. All warehouse floors require excellent flatness to allow racking to be utilised to full height of the warehouse. Burnished finishes usually go hand-in-hand with flatness as they can reflect overhead lighting and brighten indoor spaces, allow forklifts to be used safely and efficiently and provide the concrete floor with improved durability, abrasion resistance and are low maintenance.
Concrete carparks are a good investment for commercial facilities because they are easier to maintain, have a longer life span and can support heavier vehicle loads than asphalt carparks. They also are lighter in colour, helping to reduce exterior lighting costs.