1.3 Advantages and Disadvantages of Self-Compacting Concrete
Some advantages of SCC over normal concrete are:
• High performance and more calculable quality
• Compact and even surface texture
• Reduces noise pollution at construction sites
• Reduction on site manpower for all operations
• Improved durability and high strength
• Shorter construction periods
• Faster construction since no mechanical vibrators are used
• Safer and cleaner working environment
• More scope to build different structural and architectural shapes
Some disadvantages of Self-Compacting Concrete are:
• SCC is more prone to settlement cracking
• It results in rapid drying and requires increased curing to avoid increased plastic shrinkage cracking
• Increased formwork
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These are:
• Powder type SCC: This mix achieves the fluidity requirements through the reduction of the coarse aggregate volume and the use of High Range Water Reducers (HRWR). The stability comes from a low water to cement ratio with high sand to paste ratio i.e. larger amounts of fine aggregates are necessary to resist segregation in the mix.
• VMA type SCC or Stabilizers: VMAs are the viscosity modifying agents. To evolve a VMA-type SCC mix, a higher target water to cement ratio of the 0.45 has been used. The higher water content in this mix requires a smaller amount of HRWR than that in other SCC mixes. To ensure adequate segregation resistance of this mix, a relatively large amount of VMA is required. The higher amount of VMA meant that segregation could be controlled with fewer fine aggregates and a higher coarse aggregate content than in the previous SCC mixes.
• Combination type SCC: This mix is obtained by adding a low amount of stabilizer or the powder type SCC to neutralize the moisture fluctuations. The target water-to-cement ratio is 0.4. Because of the increased amount of water in this mix, a lower amount of HRWR is used than in the powder-type SCC mix. Compared to powder-type mix, the combined mix design shall have a larger coarse aggregate content and a reduced amount of fine
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On combustion of coal, the combustible matter burns and incombustible material such as rock debris results in coal ash. The rock debris varies from one source to another therefore causes variation in the properties of coal ash as well. Coal ash that has been extracted from the boiler flue gases is called fly ash and the coarser part that is collected at bottom of the furnace is called coal bottom ash. The construction industry has enormous potential for coal bottom ash as construction material. Coal bottom ash is a well-graded material and its particle size distribution is similar to that of the river sand. Bottom ash is composed of silica, alumina and iron with smaller amount of calcium, magnesium, sulfates, and other compounds. Its particles intend to have interlocking characteristics. Coal bottom ash is light in weight and more brittle as compared to natural river sand. Coal bottom ash with low specific gravity has a porous surface texture and readily degrades under loading or compaction. Coal bottom ash derived from high sulfur coal and low rank coal is not very porous in texture and is quite dense. The properties of coal bottom ash depend upon the degree of pulverization of coal, firing temperature in the furnace and type of furnace. The use of water reducing admixtures, improves the abrasion resistance of bottom ash concrete significantly in comparison to that of bottom ash
The ingredients to make this sludge is made up of sand, water, and concrete mix components. Together they make a chemical reaction that brings the liquid to its final stage of evolution, solid concrete. There are many complications at this job that puts a person's strength to the test. The process begins at the trunk of the car, where my father brings in the sand, followed by the mouth of the cement machine behind the trunk. The mouth of the cement machine is facing the truck so a person can deliver the necessary contents into the machine with ease. Once the cement machine is connected to the power and it begins to rotate, that is my death sentence to muscle soreness the next morning. I load the machine with enough water for the mix. This is a very crucial step because if ignored, I would have to deal with the unmixed cement stuck at the back of the rotating monster, like gum on a floor. Once full with water I can start shoveling the sand into the old gray spinning monster. Turn, scoop, turn, throw, turn, scoop, turn, throw. Sounds pretty easy so far, but did I mention the sand has gravel? Sand working in cooperation with many pebbles to make heavy weight, making my back send complaints to my brain. Wait... Hold up... I need to put in the cement mix. These cement bags look innocent and light to the inexperienced eye. The contents is is composed of a gray powder, like flour, that can be easily picked up by a breeze of wind.
Large holes are drilled through the slab in order to pump a thick slurry mixture under the slab. After the mixture is injected, the cement-based mixture raises and levels the slab back to normal. The curing process can up to two days. The slurry mixture is not moisture resistant, making it suspectible to erosion. As
A master mix containing the components listed in the table below was made up – with everything being kept on
Shoplifting is a major problem in today. The temptation of not paying for something, just hiding it away and saving your own money is a large factor for some people. The culprit just thinks he's getting a product for free and doesn't know what he's actually doing to himself and the community. Shoplifting effects everyone, yourself and the everyone in the local neighborhood.In this essay I'm going to explain some of the circumstances of stealing from local stores, or any store. After I've been caught stealing I found out how wrong it is and how it is a disadvantage to everyone.
This is the most recent type of concrete formwork. It’s an emerging tech for RCC construction as well as architectural design work. This materials’ flexibility creates the ability to make concrete of any shape.
These incorporate silica (SiO 2 ), sodium oxide (Na 2 O), and calcium oxide (CaO). Crude materials from which these materials are inferred are sand, pop fiery remains (Na 2 CO 3 ), and limestone (CaCO 3 ). Pop fiery remains goes about as a flux; at the end of the day, it brings down the dissolving purpose of the clump creation. Lime is added to the batch in order to improve the hardness and chemical durability of the
There are five different types of cement in the dental field each is versatile in their properties, uses, and mixing techniques. Many were traditionally used for routine cementation through the nineteen ninety’s and since have been replaced by newer makeup and mixing techniques. The selection of cement for a specific procedure requires knowledge of the chemical and physical properties of each particular cement for the specific restorative process to be performed.
PC is undoubtedly the most commonly used cement, with most other variations originating from it. There are two phases in the formation process of PC: these being the production and grinding of clinker (Khoon, 1997). For the first process, preparation of the initial compounds is
Aggregate is one of the basic constituents of concrete. Its quality is of considerable importance because about three-quarter of the volume of concrete is occupied by aggregates. One of the physical properties of aggregate that influence the property of concrete is the grading of aggregate. The grading of aggregate defines the proportions of particles of different size in the aggregate. The grading of fine (size < 5 mm) and coarse (size > 5 mm) aggregates are generally required to be within the limits specified in BS 882: 1992.
scuffing, mixes are typically designed with polymer-modified binders. Fibers are often added to the mix to reduce drain down. Many states have a specification for open-graded friction courses and asphalt treated permeable bases that may be used in specifying mixes for porous asphalt pavements.” (U.S. Department of Transportation, 2015).
When Portland cement clinker is blended with the pozzolanic materials and the result is PPC.
Continuous thickeners consist of zones similar to a batch sedimentation process except that these zones are of constant height when steady state is achieved. The design of these thickeners s based on the identification of the concentration of the rate limiting layer.
Based on the values of strengths as discussed above, Control mix strength values for 28 days (47.8 N/mm2) and 90 days (59.75N/mm2) were 20% more than 10 and 20 percent RHA.However, RHA replacement above 30 percent to 50 led to strength reduction values of about 45 to 50% of the control mix. Regarding it may fall below the standard 28day strength requirement for building and road structures and thus cannot be used.
Cold temperatures and sugar solutions retard setting of plaster of Paris while warmer temperatures and salt or borax tends to accelerate the solutions.