Aerated concrete is also commonly known as a cellular concrete (Neville and Brooks, 2010). It can be divided into two main types according to the method of production. They are foamed concrete (non-autoclaved aerated concrete (NAAC)) and autoclaved aerated concrete (AAC). Foamed concrete is produced by injecting preformed stable foam or by adding a special air-entraining admixture known as a foaming agent into a base mix of cement paste or mortar (cement+water or cement+sand+water). The AAC is produced by adding a predetermined amount of aluminum powder and other additives into slurry of ground high silica sand, cement or lime and water.
When Alite is mixed with water calcium silicate hydrate is formed, grows as a mass and provides the strength of the hydrated cement system by means of its interlocking needles. Worded equation Tricalcium silicate + Water → Calcium silicate hydrate + Calcium hydroxide Chemical reaction equation 2(3Ca•SiO2)+ 6H2O → 3CaO•2SiO2•3H2O + 3Ca(OH)2 Cement chemist notation C3S + H → C-S-H +
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.
It is an artificial material similar in appearance and properties to some of the natural lime stone rocks. It is a man made composite, the major constituent being natural aggregate such as gravel, or crushed rock, sand and fine particles of cement powder all mixed with water. The concrete as time goes on through a process of hydration of the cement paste, producing a required strength to withstand the load. The concrete becomes hardened just like rock-hard by a chemical process called hydration. Then the water reacts with the cement and creates bonding between fine and course aggregate.
3.1.2 POLYPROPYLENE FIBER IN CONCRETE Polypropylene fiber is a plastic fiber. Its raw material, derived from the monomeric C3H6 is a pure hydrocarbon similar to paraffin wax. It was suggested by Gold fen that this type of fiber can be used as an admixture to concrete in 1965 during the research for constructing blast resistant building for the U.S. Corps of Engineers. Ready mixed concrete containing polypropylene fibers can be placed using conventional methods.
Fluid Loss Control Additives: Fluid-Loss or Permeability Plugging additive are added to reduce the rate at which water from the cement slurry enters the permeable formations when positive differential pressures exist in the permeable formation. Fluid- loss additives are normally polymers such as cellulose, polyvinyl alcohol, polyalkanolamines and liquid latex (Joel,
We define concrete as a composite material which composed of coarse aggregate bonded together with fluid cement. The form of concrete is a mixture of paste and aggregates, or rocks. Cement is one of the important compositions of concrete. To produce concrete, we mix the cement with water and aggregates. After mixing, the water reacts with cement first then bonds the aggregates together and creates a robust stone-like material.
2.1 General Seismic evaluation and retrofitting strategies are mainly focused in this thesis. However, there are many good references that can be used as a starting point for research such as ATC40 manual for seismic evaluation and retrofitting of concrete buildings. This chapter focuses on recent contributions related to seismic evaluation and various retrofitting schemes and past efforts most closely related to the needs of the present work. For, the purpose of the present investigation, the literature is break down into following areas: a) Seismic evaluation. b) Retrofitting strategies.
In this study; the main purpose of using RHA is to utilize the agro waste. Rice husk ash is used as a replacement of cement at 0%, 5%, 7.5%, 10%, 12.5% and 15% in this mix. The grade of concrete is M40 cured under normal water and chemical. The Compressive strength are compared between the normal curing & chemical curing. A range of curing periods starting from, 7, 28 and 56 days are considered in the present study.