CONCRETE CONSTRUCTION ARTICLE                        

high strength concrete (1)

Introduction

Development of similar design world becoming more demanding an available of quality concrete and having height performance  as solution to create aesthetic bridge and building, but strong.In the early of 1990-an, concrete starts many utilized  to build bridge with unfold length with tower and some of its girder using high strength concrete. Bridge Tsing Ma, Hong Kong, for example, with the length of 1377 meter applies tower ( pylon) strength concrete 80 MPA.

Modern concrete

These days, because geometrical demand and construction method, many bridges become using high quality concrete and having high performance, Bridge Akihabara in Japan applies concrete with power of 120 Mpa. Even, Bridge Sakata Mirai in japan, applies having on high ultra strength reachs 180 Mpa ( around K2000).

Supartono explains basically high strength concrete is concrete having the high power, but concrete parameter quality having immeasurable height, hanging on such residing. In Indonesia, having on with above strength 50 Mpa have been classified high quality concrete  . while in Australian, 200 MPA concrete is the common. In China, with  synthetic aggregate applied, concrete can become until 300 MPA.

In development of construction of modern concrete, concrete is demanded to become high strength construction material at the same time having high performance . When pouring,is workable, low hydrate temperature ( low heat of hydration), dwindles is relative lowness at the time of drainage, good acceleration or good retardation, and easy to be pumped to high place, be some demands which must can be fulfilled high strength concrete and high performance.

Temporary, at concrete which has ossified, height strength concrete and high performance is demanded to has very height compression, better tensile strength, initial high compressive strength, ductile behaviour, airtight and water, resistant to abrasion and sulfate corrosion, penetration of low chloride,and durabel.

Figure 1 : Concrete factory

Additive material

Figure 2  Agregat form

To increase concrete performance, there is some ways which able to be done. Firstly, lessens  concrete corrosion by the way of lessening number of water in informing against concrete. Second, adds mineral additive like silicafume, copper slog or fly ash Third, adds fiber when mixing concrete. Fourth, applies concrete with self compacting concrete. In concrete making, cements is one components that hardly determines the price of concrete. One of way of depressing the price of concrete is by lessening cements usage. but, to yield high strength concrete and high performance, number of cement lessened must be replaced with other additive matter metal industrial disposal like silicafume from industry silica and copper slag which is raffle at copper baking stove, or using fly ash from coal refinery.

Mikrosilika

 Silicafume or called as also mikrosilika is raffle having content silica ( SiO₂) reachs 85-95% .Scale of a real smooth silica of about 0,1-1 µ m. smaller compared to be cements which range 5-50 µ m. If it is added at informing against concrete, the mikrosilika  will fill the chamber  among prilled cemented so that concrete will become more compactly and compact. Besides, rnikrosilika will react with C₃S and C₂S in cements and yields gel CSH-2 which will form a massive and strong gel bond in concrete.

Hereinafter, reduction of calcium hydroxide (CaOH) by Si02 will lessen element of former ettringite so lessens concrete sensitivity to sulfate attack. Hence, concrete is not easy to pierced water and not easy to experience corrosion. Because the price of mikrosilika still be expensive, generally usage of mikrosilika 3-10% only from weight cemented in informing against concrete. composition of Fly ash ( fly ash) much the same to with mikrosilika, but silica grade ( SiO2) consisting in  it lower, only around 40-65% only. Effect fly ash to concrete also much the same to compared to applies additive mikrosilika. But gel CSH-2 that yielded to be lower so that solidarity and solidity of concrete also low. To increase quality of concrete using flY ash, hence its grade have to be more , which is  20% from cements weight total in concrete. CONTINUE TO HIGH STRENGTH CONCRETE(2)