Cement Word.docx

C E M E N T

Created by : Dinar Asteria (4111010012) Gigih Muslim P. (4111010015) Muhammad Arief R. (4111010005) Nindia Andani I. ( 4111010021) Okky Irawan (4111010006) Talita Amanda P. (4111010023)

Civil Engineering Road and Bridge Construction 2011

A.

Definition Cement is one of the adhesive building material when mixed with water

is

able

to bind

to solid material

such

as sand and stone into a compact unit. Cement

used

in

construction

is

characterized

as hydraulic or non-hydraulic. i.

Hydraulic cements (e.g., PORTLAND CEMENT) harden because of hydration, chemical reactions that occur independently of the mixture's water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble.

ii.

Non-hydraulic cements (e.g. GYPSUM PLASTER) must be kept dry in order to retain their strength.

B. Function and Uses Functions of cement : 1. Cement is able to bind to solid when mixed with water. 2. Restriction of fluid movement between permeable zones 3. Provision of mechanical support of the casing string 4. Protection of casing from corrosion 5. Support of the well-bore walls to prevent collapse of formations

Uses of cement : 1. Building (floors, beams, columns, roofing, piles, bricks, mortar, panels, plaster) 2. Transport (roads, pathways, crossings, bridges, sleepers, viaducts, tunnels, stabilization, runways, parking) 3. Water (pipes, culverts, kerbing, drains, canals, weirs, dams, tanks, pools) 4. Civil (piers, docks, retaining walls, silos, warehousing, poles, pylons, fencing) 5. Agriculture (buildings, processing, housing, feedlots, irrigation).

C. Composition The main ingredient is contained in cement : 1. lime (CaO), 2. silicate (SiO2), 3. alumunia (Al2O3), 4. ferrous oxide (Fe2O3), 5. magnesite (MgO), 6. Tricalcium silicate (C3S), 7. Dicalsium silicate (C2S), as well as small amounts of other oxides 8. Kalium dioxides (K₂O) 9. Natrium dioxides (Na₂O) K₂O, Na₂O, and MgO can’t more than 5%

Main chemical compound constituents of Portland Cement.: Chemical

Chemical

Shorthand

Percent

Name

Formula

Notation

by Weight

Function Fastest hydration

Tricalcium Silicate

3CaO×SiO2

C3S

50

Overall and early strength Protect Sulphate attack

Dicalcium Silicate

Slow reacting 2CaO×SiO2

C2S

25

Responsible for gradual increase in strength

Tricalcium Aluminate Tetracalcium

3CaO×Al2O3 C3A

4CaO×Al2O3×

Aluminoferrite Fe2O3

Gypsum

CaSO4×H2O

12

Initial set and early strength Initial set and early

C4AF

8

strength Low heat of hydration

CSH2

3.5

Low hydration

Figure 3.45: Typical Oxide Composition of a General-Purpose Portland Cement (Mindess and Young, 1981)

D. Types of cement  Type I : Ordinary cement (normal) is used for concrete that is not influenced by the environment,such as sulfate, extreme temperature differences.  Type II : Used for the prevention of sulfate attack from the environment, such as for underground structures.  Type III : The resulting concrete pavement has a time of rapid (high early strength).  Type IV : Concrete is made will provide a low heat of hydration, suitable for mass concrete work.  Type V : Cement is suitable for holding the concrete with high levels of sulfate attack. C2S

C3A C4AF MgO

Cement

C3S

Type I

55% 19% 10% 7%

2.8%

2.9% 1.0%

1.0%

Type II

51% 24% 6%

2.9%

2.5% 0.8%

1.0%

Type III 57% 19% 10% 7%

3.0%

3.1% 0.9%

1.3%

Type

11%

SO3

Ignition Loss

CaO

28% 49% 4%

12%

1.8%

1.9% 0.9%

0.8%

38% 43% 4%

9%

1.9%

1.8% 0.9%

0.8%

IV Type V

E. Physical Properties of Cement a. Fineness Fineness, or particle size of portland cement affects hydration rate and thus the rate of strength gain. The smaller the particle size, the greater the surface area-to-volume ratio, and thus, the more area available for water-cement interaction per unit volume.

b. Soundness When referring to portland cement, "soundness" refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion (PCA, 1988).

This

destructive expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO). Most portland cement specifications limit magnesia content and expansion. The typical expansion test places a small sample of cement paste into an autoclave (a high pressure steam vessel).

c. Setting Time Setting tests are used to characterize how a particular cement paste sets. For construction purposes, the initial set must not be too soon and the final set must not be too late. Normally, two setting times are defined (Mindess and Young, 1981):

1. Initial set. Occurs when the cement mixing with water from plastic condition become stiffen. 2. Final set. Occurs when the cement mixing with water from plastic condition become hardened (just shape) it can’t sustain some load. d. Strength Cement paste strength is typically defined in three ways: compressive, tensile and flexural. These strengths can be affected by a number of items including: water-cement ratio, cement-fine aggregate ratio, type and grading of fine aggregate, manner of mixing and molding specimens, curing conditions, size and shape of specimen, moisture content at time of test, loading conditions and age.

F. Advantages and Disadvantages

Advantages of Cement : 1. Cement is used as a binding material 2. Cement is easy to handle and apply 3. They are suitable to contact with water.

Disadvantages From an environmental standpoint cement has a negative impact, because manufacturing it emits about a ton of greenhouse gas (CO2) into the atmosphere for every ton of cement manufactured. Then you need to add the use of fuel and emissions in transporting the heavy cement from the factory to wherever it is used. Cement is also a rather cold, unyielding material to live in.