CONSTRUCTION TECHNOLOGY.
Concrete with high quality.

What components are needed in the form of high quality concrete? We look at the history, technical explanations and its constituent materials.

MODERN CONCRETE

Today, because of the demands of geometric and construction methods, more and more bridges using high strength concrete and perform very Linggi, Bridge Akihabara in Japan using 120 MPa strength concrete. In fact, Bridges Sakata Mirai also in Japan, using an ultra high-quality concrete with strength up to 180 MPa. Nevertheless, concrete technology in Indonesia is not lagging too far. "The development of concrete technology in Indonesia over the past 20 years is very encouraging. A is a parameter that can be a cable stay bridge project in Housing Grand tour Bekasi. Pylon bridge made of concrete quality 60 MPa to condense independent (self compacting concrete) in flowwable form concrete.Jembatan Megamall in Pluit is another example of implementing high quality concrete girder beam (girder) precast prategangnya, the strength 80MPa.

Described is basically a high-quality concrete is concrete that has a high strength, but high quality concrete parameters vary considerably, depending on where located. In Indonesia, the concrete with a strength of 50 MPa was classified as high quality concrete, while in Australia, concrete berkuatan 200 MPa are common. In China, by using synthetic aggregate, have no concrete up to 300 MPa. In the development of modern concrete construction, concrete construction materials are required to be of high quality as well as high performance. In fresh concrete, easy casting in progress (workable), low heat hydrate (low heat of hydration), relatively low shrinkage upon drying, has a high initial bind time (acceleration) or delay (retardation) is good, and easily pumped into higher place, are some demands that must be met quality and high-performance concrete.

Meanwhile, the concrete has hardened, high strength concrete and high performance are required to have high compressive strength or very high, better tensile strength, high initial compressive strength, ductile behavior (clay), air tight and water resistant to abrasion and corrosion sulfate, chloride penetration is low, expansion of low shrinkage, and durable.

Additives.

To improve the performance of concrete, there are several ways you can do. First, it reduces porosi concrete by reducing the amount of water in the concrete mix. Second, add the mineral additives seperri silicafume, copper slog or fly ash (fly ash). Third, add fiber to the concrete. Fourth, using concrete with self-compacting properties or self compacting concrete. In the manufacture of concrete, cement is one of the most expensive components that determine the price of concrete. One way to suppress the price of concrete is to reduce the use of cement, but to produce high strength concrete and high berkineria, reduced the amount of cement to be replaced with other additives. The experts recommend to use industrial waste silicafume of industrial metals such as silica and copper slag is a waste of the copper furnace, or the use of fly ash from coal combustion waste.

Mikrosilika.

Silicafume also called mikrosilika is waste that contains silica (SiO2) reaches 85-95%. Silica particle size ranges from 0.1 to 1 μm is very smooth, smaller than grains of cement in the range 5-50 μm. If added to the concrete mix, will fill cavities between the grains of cement so that the concrete will be more compact and dense.

 In addition, rnikrosilika will react with C3S and C2S in the cement and produce CSH gel-2 that will form a strong bond and a solid gel in concrete.

Furthermore, the reduction of calcium hydroxide (CaOH) by Si02 will reduce ettringite forming elements, thereby reducing the sensitivity of concrete to sulfate attack. Therefore permeable concrete is not easy and is not susceptible to corrosion. Because the price is still expensive mikrosilikon, generally use mikrosilika only 3-10% of the weight of cement in the concrete mix.

 The composition of the fly ash (fly ash) is almost the same as mikrosilika, but the levels of silica (SiO2) is contained in it is lower, only about 40-65% only. The effect of fly ash to concrete is also almost the same than using additives mikrosilika. But the CSH gel-2 produced lower vang so that the compactness and density of concrete is also low. To improve the quality of concrete using fly ash, the measure should be more, which is 20% of the total weight of the cement in concrete.

Copperslag.

Copperslag is one of the ground granulated blast furnace. Slag (GGBFS) or slag and furnace. The composition of the material is close to the cement and the price is relatively cheaper. Copper slag as an additive that also can replace cement in the concrete mix. Often in practice in the field percentage is quite high, ranging from 20-65%.

Copper slag partially replace cement provides several advantages. First, the heat of hydration and shrinkage of concrete expansion will be reduced, thus improving the performance of concrete. Second, the price will be cheaper concrete. Third, by reducing cement consumption, will also mean reducing the energy in the cement manufacturing process and reduce the pollution caused by the cement production process. Fourth, using waste materials, meaning real has applied material technology berkelanjulan (sustainable material technology). "The use of waste is a form of participation we preserve the environment".

Research conducted by the department showed that partial replacement of cement with copper slag, with a share of 10-40%, can produce concrete strength 60-75 MPa, depending on the fineness of copper slag. There are two sizes rnacam subtlety used, ie 90 'cm2 / gm and 1184 cm2/grm. The more refined copper slag, the higher the compressive strength of concrete. This test uses the ratio of cement water content of about 0.3.

Fiber material.

In addition to sewage and industrial metal, fiber (fiber) can also improve the performance of concrete, known as fibrous concrete. Here micro fiber serves as reinforcement that protects the concrete from cracking, increased tensile strength and flexural indirectly. Fiber also increases the compressive strength and ductility of concrete, improve kekedapan concrete, as well as increase the durability of reinforced concrete to loads and shock loads. Micro reinforcement system made from these fibers work based on mechanical principles, ie based on the bond (bond) between fiber and concrete, not chemically .. Therefore Beron fibrous composite material would be a material that is not easily cracked.

Chemical processes in concrete will not be affected by the fiber and will not harm the concrete hardening process in the short and long term. Some types of fiber materials that can be used in concrete, among other natural fibers (hemp, abaca), synthetic fibers (polyester polyproplene.), nylon), steel fiber and fiber glass.

Improving the tensile strength and flexural, improving ductility and ability to absorb energy while deforming, reduce cracking caused by concrete shrinkage, improve fatigue resistance (recurring expenses) and increase the resistance of impact (impact load) are some of the benefits of fiber concrete.

Self compacting concrete.

A new concept for creating high-performance concrete is by using self compacting concrete form flowoble Concrete. This concept is a solution to the concrete can be poured easily and quickly without the need for compressed / vibrated. Concrete flows easily, filling cavities reinforcement meeting without experiencing bleeding or segregation, even in difficult places.

In general, self compacting concrete produced with super plasticizer additives based polymers, mikrosilika, as well as other additional specific and aggregate sizes smaller than 20 mm, can produce high quality and high performance concrete. It is recognized that the development of technology has lagged behind the national concrete with developed countries. Not many mastering engineers and technology steeped in high strength concrete and high performance, especially in the technology of mixing material. It also hampered the quality of materials in Indonesia.

One principle that must be understood by the power production of concrete is to be able to make high strength concrete with materials that are around them. "If they all hold that principle, the concrete becomes materiaI an economical and fun".