(Newman and Choo, 2003) 184.108.40.206.1.1 Lightweight aggregate concrete: Lightweight aggregates are used to produce lightweight concrete when the weight of aggregates is lower than 1120 kg/m3 (Mehta and Monteiro, 2006). Lightweight aggregates have many sources: a)
Polymer Impregnated Concrete (PIC)- Improved damping capacity (High damping at lower frequency range Hollow Composites Sphere- It consists of hollow spheres as filler and epoxy resin as matrix material. Reduced weight. Higher thermal coefficient of expansion than steel. Hollow sphere consists of a mixture of metal oxides or plastic and size ranges from 10µm to 2mm. Cementitious Composite Materials- Cement as binders.
Concrete, a strong, durable material composed of cement, aggregate, and water, is the most used building material in the world. The improvement of concrete is needed and essential in order to increase the performance and sustainability. Good quality concrete requires adequate compaction during casting by skilled labours, which have numerous disadvantages. Self-compacting concrete (SCC), with self-compacting ability enables the concrete to self-levelled and compacted under its own weight without internal or external compaction. The highly fluid nature of SCC makes it suitable for placing in difficult conditions and in sections with congested reinforcement.
Aggregate grading is very important in relation to the properties of concrete. This does not directly measure the size of the aggregates but instead the aggregates are put through a sieve and the mass retained is measured. (Owens, 2013) 3.1.1) Coarse aggregates A coarse aggregate is the portion of aggregates that does not pass through the 4.5mm sieve because they are to big. These aggregates are known as stone (Owens, 2013). As can be seen in the graph below, there is a relationship between corase aggregate and sieve size, the bigger the sieve size the more corase aggregates are present.
The H-shaped beams will be more preferable in this case since; the beams will be able to with stand the shear forces and stress exerted by bending and through shear loads. Due to its shape, it is able to provide efficient support at the top and at the bottom. Its however disadvantaged in that, it is not efficient in carrying torsion as there is preference of hollow structures in this case. The beams are made of steel, which is the most ideal material for use. The load exerted on the beams will be caused by; the load from the self weight caused by the deck, loads resulted to by the live loads, weight exerted due to car skidding as well as effect of braking and horizontal loads as a result of temperature and movements such as wind.
CHAPTER 3 Project Description 3.1 THEORITICAL CONCEPTS ABOUT FIBER REINFORCED CONCRETE Concrete being a brittle building material and having low tensile strength is unfit to resist tension until duly reinforced. The concept of using fibers to reinforce building materials is not a nascent concept this method has been old and been run by intuition. Hoarse hairs and straws had been used in old times to prevent plaster material from cracking. More recently when Portland cement started evolving, attempts were made to enhance the properties of the cement by adding fibers. The concept of adding fibers to overcome the inherent behavior of concrete of showing brittle failure under tensile load.
This method need minimum capital outlay. However, the strength level is in modest state as high fibre concentration is difficult and the fibre are oriented in three dimension. The premixed material is usually placed into a mould and vibrated but it can alternatively be applied by using trowel or spray. Thus, the glass fibre added at the end of concrete mix cycle in order to avoid glass fibre strength from decreasing. (Neal et, al, 1978) Figure 2.7: Premixed Method.
INTRODUCTION ABOUT DAMS WHAT ARE DAMS? A dam is a hydraulic structure of fairly impervious material built across a river to create a reservoir on its upstream side for impounding water for various purposes. A dam and a reservoir are complements of each other. Dams are generally constructed in the mountainous reach of the river where the valley is narrow and the foundation is good. Generally, a hydropower station is also constructed at or near the dam site to develop hydropower.
and steel, both of which have entirely different mechanical properties. Steel can be considered a homogeneous material and its ft and ductility are very high. Conc.. is, non-homogenous making from different materials. The evaluation of mechanics of RC members made of two materials is very difficult because one of the materials, which is Conc., behaves differently in tension than in compression and may be considered to be inelastic. And the second one is steel whose properties define well.
The most common applications are pavements, tunnel linings, pavements and slabs, shotcrete and now shotcrete also containing silica fume, airport pavements, bridge deck slab repairs, and so on. There has also been some recent experimental work on roller-compacted concrete (RCC) reinforced with steel fibers. The list is endless, apparently limited only by the ingenuity of the engineers involved. The fibers themselves are, unfortunately, relatively expensive; a 1% steel fiber addition will approximately double the material costs of the concrete, and this has tended to limit the use of SFRC to special applications. The largest application for steel fiber reinforced concrete is floor slab construction, although it’s use as a replacement for or complement to structural reinforcement in other applications is growing fast.