Cement process and types
Post on 25-Jun-2015
335 Views
Preview:
DESCRIPTION
Transcript
1
PensyarahPensyarah
Prof. Madya Dr. Mohammad IsmailProf. Madya Dr. Mohammad Ismail
Fakulti Kejuruteraan AwamFakulti Kejuruteraan AwamUniversiti Teknologi MalaysiaUniversiti Teknologi Malaysia
20092009
2
Cement
Aggregate (fine + coarse)
Admixture
Water
3
• INTRODUCTION– Common construction material, the properties may
be predetermined by design, selection of constituent materials, and quality control
– The constituent materials of concrete are• cement, aggregates, water and admixtures
– Ingredients mixed → molded → hydration → concrete
CEMENT
4
Cement
• Cement is any material that binds or unites – essentially like glue.
• In civil engineering or construction, the word cement or “cementitious material” refer to an ingredient in concrete, mortar or grout
5
Cement
Is the product obtained by grinding clinker formed by burning raw-materials (argillaceous and calcareous) primarily consisting of lime (CaO), silicate (SiO2), alumina (Al2O3), and iron oxide (Fe2O3)
6
Advantages/ Kebaikan
• Cheap
• Flexibility - (concrete, mortar, grout…)
• Finishes/ Penyudah - versatile
• Compression strength – high
• Protection/ Mengawal - keluli
7
Disadvantages
• Low tensile strength/ Brittle (Rapuh)/
• High density/ Berat
• Deteriorate (Boleh rosak) – suceptable to frost/ chemical attack
8
Characteristic of cement
• Setting and hardening when mix to a paste with water
• Cohesive and Adhesive
9
History of Portland Cement
• 1824 – patented by Joseph Aspdin
• Materials to produce cement were found on the English Isle of Portland
• Thus, called PORTLAND CEMENT
10
Cement
• Argillaceous + Calcareous
Silica Lime
Alumina
Ferum oxide
Argillaceous – clay, sandstone, shale
Calcareous – limestone, chalk
11
Cement
• Hydraulic cement – able to set and harden under water e.g. OPC, Slag Cement, ggbs
• Non-Hydraulic cement – will not set and harden under water but require air to harden e.g. lime, gypsum
12
Manufacturing Process
Two processes:
• Wet Process – softer materials (clay + chalk)
• Dry Process – harder materials (shale + limestone)
13
1. Grinding and mixing of raw materials
2. Burning in a rotary kiln
3. Cooling, grinding and sieving
4. Storing, packing and distributing
Steps in manufacturing process
14
Manufacturing Process
15
16
Wet Process
1. Materials being ground and mixed with the correct proportions
2. The mixture in a slurry form is fed into a rotary kiln where it is heated/burnt to a temperature of 1500 oC to form clinker
17
Wet Process
3. Cooling and grinding – Gypsum (CaSO4) is added during the grinding process to prevent flash setting
4. Storing – stored in silo
18
Burning (wet process)
• 100 oC – water is driven off
• 850 oC – limestone changes to calcium oxide and CO2 is liberated
• 1500 oC – CaO reacts with SiO2 to form Calcium Silicate CS
• CaO reacts with other compounds to form Calcium Aluminat (CA) and Calcium Aluminoferit (CAF)
19
Dry Process• The process is relatively the same as wet
process except in dry process the raw materials (harder materials) are mixed in dry condition.
• Small amount of water is added to form 12mm in diameter ‘balls’
• The ‘balls’ are burnt in a rotary kiln and the chemical reactions are the same as wet process
20
21
Kursus Forensik Kejuruteraan Pembinaan
Pegawai BPR Malaysia2 Ogos – 7 Oktober 2004
Hotel Seri Malaysia
Johor Bahru
Ordinary Portland Cement (OPC)
Rapid Hardening Portland Cement (RHPC)
Sulphate Resisting Portland Cement (SRPC)
Modified Portland Cement (MPC)
Low Heat Portland Cement (LHPC)
Portland-Blastfurnace Cement (PBC)
Portland-Pozzolan Cement (PPC)
Others
Types of Portland Cement
22
Cement differing in chemical composition may exhibit different properties when hydrated
23
Ordinary Portland Cement
• By far the most common cement used in general concrete construction when there is no exposure to sulphates in the soil or groundwater
• Minimum fineness of 225 m2/kg
• Rate of hardening is moderate
• Standards; BS 12, MS 522
24
Rapid Hardening Portland Cement (RHPC)
• Rapid strength gain due to higher C3S content (70%)
• Minimum fineness of 325 m2/kg• Used when formwork is to be removed early for
reuse or where sufficient strength for further construction is required quickly
• Should not be used in mass concrete construction or in large structural sections because of its higher rate of heat development
25
RHPC
• For construction at low temperatures, the use of RHPC may provide a satisfactory safeguard against early frost damage
• The setting time and chemical composition of RHPC and OPC is relatively the same
26
Sulphate Resisting Portland Cement
• This cement has low C3A (3.5%) content so as to avoid sulphate attack from outside the concrete
• Minimum fineness of 250 m2/kg• Active salts are magnesium and sodium sulphates
• Sulphate attack is greatly accelerated if accompanied by wetting and drying (splash zone)
• The heat develop by SRPC is not much higher than the low-heat cement, which is an advantage
27
Portland-Blastfurnace Cement
• Made by intergrinding or blending Portland cement clinker with granulated blastfurnace slag
• Known as slag cement• Slag contains lime, silica and alumina, but not in
the same proportions as in Portland cement• Minimum fineness of 275 m2/kg• Early strength are generally lower than OPC but
later strength are similar or even higher
28
Cont.
• Typical uses are in mass concrete because of low heat of hydration and in seawater construction due to better sulphate resistance
(lower C3A content) than with the OPC
• The amount of slag replacement between 25 to 70% of the mass of the mixture
29
Portland-Pozzolan Cement
• Made by intergrinding or blending pozzolans with Portland cement
• A pozzolan is a siliceous or siliceous and aluminous material which itself possesses little or no cementitious value BUT in finely divided form and in the presence of moisture, chemically react with Ca(OH)2 - liberated during the hydration of Portland cement to form compounds possessing cementitious properties
30
Cont.
• Portland-Pozzolan cement gain strength slowly and therefore require curing over a comparatively a long period, but the long-term strength is high
• Amount replacement between 25 to 40%
• More durable than OPC
31
Compound Chemical formula Abb. Percent
(range)
Rate of reaction
with water
Tricalcium silicate
3CaO.SiO2 C3S 35-65% Medium
Dicalcium silicate
2Cao.SiO2 C2S 15-40% Slow
Tricalcium Aluminate
3CaO.Al2O3 C3A 0-15% Fast
Tetracalcium Aluminoferrite
4CaO.Al2O3.Fe2O3 C4AF 6-20% Medium
Principal Compounds of Portland Cement
32
Alkalis in Cement
• Na2O and K2O
• May cause problem – Alkali Silica Reaction
33
PROBLEMS
1. What are the three main compounds in the raw materials for the manufacture of cement (limestone or chalk
CaO, Clay or shale Silica SiO2 and Alumina Al2O3)
2. What is the purpose of adding gypsum to cement (add 2-5% gypsum to retard the setting time of cement)
3. What are the four major compounds of portland cement
4. Which is the most reactive compound in portland cement
5. Name a nonhydraulic cement6. Name two hydraulic cement
34
Terima Kasih
top related