Introduction
Concrete is most widely used material for various applications in this world. India is second largest producer of concrete in world. As this is used in various applications its base properties which are obtained by preparing concrete with required raw materials must be enhanced by adding some other material to it. There comes the role of admixtures by which one can extract required property from concrete. There are various two basic classifications of admixtures. Chemical and Mineral admixture. There are various types of mineral admixtures. Most of mineral admixtures are by-products available from some production industry. Silica fume is a mineral admixture which is obtained as by-product of silicon industry is a costliest material but is very desirable material for normal concretes. Footprint of Nanotechnology which is defined as science of controlling the properties at nanometer scale which can make revolutionary changes in bulk material properties [23] in construction field has great impact in improving the properties of concrete . There are many types of nano-materials like nano-silica, nano-alumina, carbon tubes etc.. This paper describes how the properties of concrete are enhanced by adding nano-silica to it and compares with concrete containing microsilica. Both nano-silica and micro-silica are siliceous admixtures having higher contents of amorphous silica but nano-silica is the one having 1/10th size of silica-fume which is major advantage for nano-silica to enhance different properties of concrete to larger extent than microsilica.
Silica Fume
It is by-product of silicon industry and contains very large amounts of amorphous silicondioxide (about 90%). (ACI-116R)[1]
It is 100 times smaller than cem...
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...ay be due to reduced size and total volume of pores. Not much difference was found between addition of NS or MS to these concretes.[16]
Effect on self-compacted concrete
On addition of NS to self-compacted concrete one can observe reduction in bleeding, segregation and flowability. Experimental results showed improved compressive strength, split tensile strength and flexural strength. Higher electrical resistivity and resistance to chloride ion penetration was also observed in NS incorporated Self compacting concretes.[17][18]
Effect on rice husk ash concrete
Author observed that overall performance of concrete was increased and there is huge reduction in water absorption [19]
Effect on eco-concrete
Delayed setting and very low early strengths are major defects of eco-concrete which can be counteracted by incorporating NS into these concretes. [20]
Conclusion: In support of my hypothesis, it is found that the mystery powder is one of the five known compounds. Through experimenting the chemical reaction in spot plates, it is concluded that the mystery powder is icing sugar. It was fairly straightforward because we just have to see which substances matched the reaction of the mystery powder. All in all, my hypothesis is correct and through researching the interpretation, icing sugar is the mystery substance.
made from a form of aluminum soap mixed with the acid (Time, 2000). The formula was said to have
they're not. Concrete is to cement as a cake is to flour. Concrete is a mixture
Most people may not realise but concrete plays a vital part in our lives daily. It shapes and creates the built environment in which we are surrounded by, such as schools, bridges, roads, housing, hospitals, dams and so much mores. Concrete is the most used man made material in the world, averaging around 3 tonnes annually for each person. In comparison with other building materials such as wood, steel, plastic and aluminium, over twice as much concrete is used globally than any of these materials. It is the material choice of most purposes due to its strength, durability, thermal mass and its cost.
Concrete and masonry products contain silica sand and rock containing silica. Since these products are primary materials for construction, construction workers may be easily exposed to respirable crystalline silica during activities such as the following:
In this report, we will introduce and illustrate on precast concrete, pre-stressed concrete, ready-mix concrete, reinforced concrete, terrazzo and Urbanite in details.
These materials present some unique desirable properties which cannot be met by using OPC only (Neville, 1995a). For producing high performance concrete (HPC), it is well recognized that the use of supplementary cementitious materials (SCMs), such as silica fume (SF), ground granulated glass blast-furnace slag (GGBS) and fly ash (FA) are necessary. The concept of HPC has definitely evolved with time. Initially it was equated to high strength concrete (HSC), which certainly has some merit, but it does not show a complete and true picture. There is a need to consider other properties of the concrete as well which sometimes, may even take priority over the strength criterion. Various authors proposed different definitions for HPC. According to Forster (1994), “High Performance Concrete is a concrete: made with appropriate materials, combined according to a selected mix design; properly mixed, transported, placed, consolidated and cured so that the resulting concrete will give an excellent performance in the structure in which it is placed, in the environment to which it is exposed and with the loads to which it will be subjected for its design”. Thus, HPC is directly related to durable
As concrete is plastic material in Green State it has to kept in enclosure till its harden. This enclosure is known as ‘ Formwork or Shuttering’.
Moreover, the demolition of concrete structures and disposal of the associated wastes is an environmental problem. Rejected construction materials and building derived materials (BDM) constitutes the single largest portion of these wastes, amounting to 2.40 – 3.67 million tonnes per annum (Meyer, 2004). For example, in the US, approximately 49% of the utility wastes (e.g. fly ash which can be produced while generating electricity from coal) are simply landfilled, 41% are contained in surface impoundments, and about 10% are disposed of by discharging into old quarry operations (Provis and van Deventer, 2009). Thus, it is imperative to adopt innovative technqiues to utilize rejected concrete wherever applicable, instead of producing fresh
...nerally their major constituent is also fine aggregate. Confusion sometimes exists over the difference between the terms fine aggregate and sand, there is in fact no difference the two words may be interchanged. Fine aggregate quality is affected by a number of factors: The mean particle size, grading, presence of impurities, shape, texture of the paricles. The selection of suitable aggregates, which are capable of producing a product with the optimum properties, is most important. The design of mortar mixes is based on the concept that the voids in the fine aggregate, which are generally in the range 25- 40%, will be filled with binder. Where the voids are not completely filled there is an increasing risk that the mortar will not be durable. Aggregate may be natural, manufactured or recycled [EDUCATIONAL GUIDE TOAGGREGATES, Experts in Mortar, Cemex Mortar][3][4].
The improvements involved a combination of improved compaction, improved paste characteristics and aggregate matrix bond, and reduced porosity. In these systems a significant decrease in water-to-cement ratio is achieved through the use of plasticizers, further enrichment of some properties have been obtained through the addition of mineral micro fillers (supplementary cementing or pozzolanic materials such as silica fume and fly ash). Despite the fact that high performance concrete has the same basic ingredients as the normal concrete, its much higher qualitative and quantitative performances present them as new materials. High performance concrete is one in which certain characteristics are developed for a particular application and environment. High performance concrete gives excellent performance in the structure in which it will be placed, in the environment to which it will be exposed, and with the loads to which it will be subjected during its design life. Self Compacting Concrete (SCC) is a High performance concrete which has been developed for use in situations where sufficient vibration by external agency is difficult and reinforcing steel is highly congested. Self Compacting Concrete is a remarkable achievement in the construction industry that helped to surmount the problems associated with cast-in-place concrete. Unlike normal concrete, Self Compacting Concrete is unaffected by the skill of workers, the shape and amount of reinforcing bars or the arrangement of a structure and, due to its high-fluidity and resistance to segregation it can be pumped longer distances. Professor Hajime Okamura was the first who propounded the concept of Self Compacting Concrete in 1986, but the prototype was first developed in 1988 in Japan, by Professor Ozawa at the University of Tokyo. Self Compacting Concrete was developed at
Concrete is an extremely versatile and durable building material. Concrete can be used to build long lasting structures even in very harsh environments when it is made with adequate constituents and mix design and properly handled .performance problems that may arise occasionally are often due to the use of materials that do not full fill minimum quality requirements, unsatisfactory specifications or due to inappropriate construction methods.
Valeria Corinaldesi, et al. evaluated compressive strength of concrete. The Compressive strength of concrete was determined at 3, 7 and 28 days age of curing. The addition of both red and blue pigments caused a certain strength loss never higher than 3 MPa. Moreover, the use of CaO together with shrinkage reducing admixture (SRA) allowed to fully recovering the slight strength loss due to the red pigment addition. At the dosage of 20 kg/m³ slightly reduces concrete compressive strength. The use of shrinkage reducing admixture and CaO proves to be very effective in reducing the risk of concrete cracking and it also gives positive contribution on concrete compressive strength
As we know nowadays concrete plays an important in civil engineering field. Use of concrete has also overcome the brick masonry.
Conventional normal cement concrete is normally used as construction material of buildings. The impervious nature of concrete