High performance lightweight concrete is produced by carefully mixing specified amount of cement, sand, lightweight aggregate, different pozzolans such as fly ash, silica fume, shale, metakaolin, calcined clay and superplasticizer.
Various applications of high performance lightweight concrete are discussed.
Fig.1: High Performance Lightweight Concrete Used in the Construction of Multistory Building and Bridge Structure
Applications of High Performance Lightweight Concrete
Application of high performance lightweight concrete involves:
- Construction of precast structure
- Construction of Buildings
- Construction and rehabilitation of Bridge structures
- Construction of marine structures
1. Construction of Precast Structure
One of the main applications of high performance lightweight concrete is in the construction of precast structures including bridges, parking garages, and long span roof framing.
Because, self weight of high performance light weight concrete is smaller than that of conventional concrete, greater bridge spans can be constructed, without facing transportation and erection problem which possibly occur when conventional concrete used to construct the same prestressed concrete member.
Figure 2 show Wabash Bridge constructed using precast high performance lightweight concrete. The post tensioned tee girder bridge length is 53.4m and its depth 2.3m and each of girder weight is about 96 tones.
Not only does the weight of structure reduced by 17% but also the total cost decreased by 18%. So, it can be clearly noticed that this type of concrete improves construction efficiency and reduce construction cost.
Finally, high performance lightweight concrete has been used for long span roof framing with nearly 37 m span length.
Fig.2: Wabash River Bridge
2. Construction of Buildings
Numerous structures have been constructed using high performance lightweight concrete. High performance lightweight concreted to for both structural and aesthetic purposes.
It used to solve problems which may be encountered when conventional concrete is utilized. For example, when the north pier apartment as shown in Figure 3 was constructed, high performance lightweight concrete used to prevent delicate timing consideration that was necessary to avoid the formation of cold joints.
Fig.3: North Pier Tower, Chicago, USA
Finally, high performance lightweight concrete used to construct floor slabs of the Bank of America (Figure 4) to reduce slab dead load and achieve three hours fire resistant rating.
Fig.4: Building of Bank of America
3. Construction and Rehabilitation of Bridge Structures
High performance lightweight concrete has been used in the construction of various elements of bridge structure for example decks, beams, girders, and piers. It provides high concrete compressive strength with high air content and consequently reduce maintenance works dramatically. This is the main factor that motivate bridge designer to select this type of concrete.
High performance lightweight concrete are used in the construction of new bridge structure and rehabilitation of existing bridge structures as well.
It offers several advantages for example, bridge deck can be widened without changing other structural elements such as piers, increase ultimate load carrying capacity of the bridge, reduced seismic inertia forces, concrete cover can be increased with the same weight used when conventional concrete is used, longer spans safe pier cost, thicker slabs can be constructed and hence deck geometry would be enhanced.
Finally, Figure 5 shows detailed section of Whitehurst freeway in the United States. This freeway rehabilitated with high performance lightweight concrete and consequently dead load reduced and total load carrying capacity increased.
Fig.5: Sections of Whitehurst Freeway in USA, A: Existing section of the bridge, B: Rehabilitated section of the bridge, a total of 205Kg/m2 reduced because of high performance lightweight concrete application in the rehabilitation process
4. Construction of Marine Structures
High performance lightweight concrete is substantially suitable construction materials to be used in the construction of marine structures. This is because offshore platforms are frequently constructed at shipyards and then floated and towed to the construction site and finally installed at specified location.
This construction process could be improved if the weights of marine structural elements are decreased. This reduction can be achieved by using high performance lightweight concrete.
High performance lightweight concrete can be used to meet floating and draft requirements as in the case of Tarsuit caisson retained island in British Columbia. Added to that, it is employed to enhance buoyancy of marine platforms.