Portland cement is made to go through several steps, so it is very smooth and has adhesive and cohesive properties. Semen is obtained by burning simultaneously a mixture of calcereous (containing calcium carbonate or limestone) and argillaceous (containing alumina) with a certain ratio. concrete batching plant
By making easy steps:
1. The content of portland cement in the form of lime, silica and alumina, as the base material
2. Third base material was mixed and burned at a temperature of 1550 ° C and into clinker
3. Then removed, cooled and pulverized into powder like powdered
4. Normally plus gypsum or calcium sulfate (CaSO4) is approximately 2 to 4 percent as a bonding time controller
5. Then put into the bag with the weight of each bag of 40 Kg or 50 Kg to be marketed.
d. Attributes of Portland Cement
Kimi arrangement on portland cement:
0.5 to 6
0.5 to 4
Soda / Potash (Ma2O + 2O)
0.5 to 1
Although complex, but basically there can be mentioned 4 fourth most important compounds such compounds are:
Tricalcium silicate (C3S) or 3CaO.SiO2
Dicalcium silicate (C2S) or 2CaO.SiO2
Tricalcium aluminate (C3A) or 3CaO.Al2O3
Tetrakalsium aluminofert (C4AF) or 4CaO.Al2O3.Fe2O3.
1) hydration of cement
Cement hydration process takes place when the water in contact with the direction from the outside to the inside, meaning the results of hydration settles on the outside and a core that has not been hydrated cement on the inside is gradually hydrated so that the volume decreases. Hydration beginning of the process has been slow, between 2-5 hours which is called (the induction period or active) before accelerating after the skin surface rupture. In the next stage of hydration, the cement paste into a gel (very finely granulated result of hydration, has a very large surface area)
2) the strength of cement paste and the amount of water used
The strength of the hardened cement paste depends on the amount of water used when hydration process takes place. Basically, the amount of water required by the hydration process is only approximately 25 percent of the weight of the cement, the addition of water will reduce strength after hardening. However, the excess water (lubricants) will also result in more porous pasta.
3) The physical properties of cement
Portland cement used for the concrete must have a certain quality that has been set in order to function effectively, periodic examination needs to be done whether in a dry powder or a cement paste that has been hard, also made of cement concrete properties of the cement tersebut.ada important, namely;
a) the fineness of grain
The reaction between cement and water starts from the surface of the cement grains, so the surface area of the cement grains (weight of cement are the same), the faster the hydration process. In general, fine grained cement that increases the cohesion of fresh concrete (fresh concrete) and may also reduce the bleeding, but also increased tendency to shrink more concrete and facilitate the occurrence of shrinkage cracks.
b) Time bond
Cement when mixed with water to form a gel that gradually becomes less plastic, and eventually becomes hard. In the first stage of this process is achieved when the cement paste rigid enough to withstand the pressure. The time to reach this stage is called bonding time. Bonding time is divided into two, namely;
a. Initial bonding time is the time from when mixing cement and water until keplastisannya loss of properties.
b. Final bonding time is the time reaches the pasta into hard times.
In ordinary portland cement, the initial bonding time should not be less than 60 minutes and the final bonding time can not be longer than 480 minutes (eight hours)