Cement PDF

Chemistry Cement Section 1 Eng. Sandra Alber  Topic of Tutorial : 1 - Cement 2 - Green Concept 3 - Ideal Gases 4 - Real Gases 5 - Solution 6 - Thermochemistry 7 - Waste Water  Class Work : Section contents 1. Mortar Uses Types 2. Cem...

Chemistry Cement Section 1 Eng. Sandra Alber  Topic of Tutorial : 1 - Cement 2 - Green Concept 3 - Ideal Gases 4 - Real Gases 5 - Solution 6 - Thermochemistry 7 - Waste Water  Class Work : Section contents 1. Mortar Uses Types 2. Cement Definition Most famous cement Raw materials Manufacturing process of cement Main components of Portland cement Reactions of cement components with water Tests applied to the cement industry Other types of cement 1 - Mortar 1- Uses In building to help the coherence of its components 2- Types Aerated Mortar Hydraulic Mortar Solidify when it reacts with air Solidify when it reacts with water Mixture of sand and slacked lime Mainly composed of sand and Ca(OH) 2 Cement Ca(OH)2 +Co2 CaCo3+H2o Heavy load (enhance coherence) No heavy load 2- cement : 1. Definition: Synthetic building material , have binding ability upon mixing with water and not disintegrate in water 2. Most famous cement: is Portland cement 3. Raw material (Made of ): 1- Lime stone CaCo3 2- kaolin clay Al2O3.SiO2.2H2o 3- Ferric (Iron) oxide Fe2O3 4 - Manufacture Process of Portland cement Lime stone + Clay + Fe2O3 Cooling Storage Grinding Crushing Clinker (5% gypsum) Retarding agent Mixing Rotary Furnace Packing (Water) Wet grinding Filtration Ferric oxide  Rotary furnace Properties Function 1. Length 60 to 120 m 1. Remove physical water 2. Diameter 3 to 4 m 2. Remove chemical water 3. Lined with refractory brick 3. Calcination reaction : 4. Tilted from the horizontal level by CaCo3 CaO +Co2 5 – 6⁰ 4. Form clinker (1400 ℃ ) 5. Fire flame extends to about quarter of the furnace length 6. Temperature at flame 1500 ℃ , at top 400℃ ( not homogenous) clinker: 7. 1-2 rotation / minute Circular porous Diameter 3 – 6 cm  5- Main components of Portland cement : 1. Tricalcium Silicate C3S (3CaO.SiO2) 2. Tricalcium Aluminate C3A (3CaO. Al2 O3) 3. Dicalcium Silicate C2S (2CaO.SiO2) 4. Tetra calcium aluminoferrite C4AF (4CaO.Al2O3.Fe2O3) CaCo3 CaO +Co2 (clay) Al2O3.SiO2.2H2o Fe2O3 Notes : Fe2O3 (Ferric Oxide) : Presences in mixture of the raw materials ,helps in the formation of the clinker at low temperature (around 1300℃ ) May be present in raw clay or may be added to mixture. Work as (fluxing agent). CaSo4.2H2o (Gypsum): Might be added to the clinker (5% ) Work as (retarding agent) Retards the reaction of cement with water (retarded cohesion). 6-Reactions of cement components with water : 1. C3S React with water ( 6 min 3 2. C3A hours) 3. C4AF Setting period time that start to lose its plasticity The reaction takes 4. C2S place in the first four weeks Responsible for Harding 6-Reactions of cement components with water : 1. C3S +H2O → Ca(OH)2 + calcium hydrosilicate - responsible for the cohesion of mortar - quick reaction 2. C3A +H2O → X + Ca(OH)2→ Calcium hydroaluminate - responsible for the setting time (6 min→3 h) 3. C2S + H2O → Ca(OH)2 +Silicon Hydroxide - responsible for the hardness - slow reaction (4 weeks→ years ) 7- Tests applied to the cement industry: 1. Hydraulic index : 𝑪𝒂𝑶 𝑺𝒊𝑶𝟐 + 𝑨𝒍𝟐𝑶𝟑 + 𝑭𝒆𝟐𝑶𝟑 Should be lie between 1.7 and 2.2 % 7- Tests applied to the cement industry: 1. Hydraulic index : Nowadays , the hydraulic index is replaced with lime saturated test : 𝑪𝒂𝑶−𝟎.𝟕 𝑺𝑶𝟑 𝟐.𝟖𝟓 𝑺𝒊𝑶𝟐+𝟏.𝟐 𝑨𝒍𝟐𝑶𝟑+𝟎.𝟔𝟓 𝑭𝒆𝟐𝑶𝟑 Which should lie between 0.66 and 1.02 The decrease of CaO cause decrease in C3S which is important for setting process and early strength. 7- Tests applied to the cement industry: 1. Hydraulic index : The increase of these percentage more than 1.02 will produce free lime which reacts with water and produces high amount of heat that vaporizes some water and the water vapor causes cracks in mortar. Less than 0.66 slower in setting More than 1.02 cracks in mortar 7- Tests applied to the cement industry: 2. Silica index: The percentage should be lie between 2 and 2.5 : 𝑺𝒊𝑶𝟐 CaO (C2S) 𝑨𝒍𝟐𝑶𝟑 + 𝑭𝒆𝟐𝑶𝟑 (C3A ,C4AF) More than 2.5 mean that → 𝑺𝒊𝑶𝟐 ↑ → C3S & C2S ↑→ setting & hardness↑. 7- Tests applied to the cement industry: 2. Silica index: Less than 2 means that : 𝑺𝒊𝑶𝟐 ↓ → C3S & C2S ↓ → setting & hardness ↓(Rapid poor setting) More than 2.5 Rapid in setting Less than 2 Slower in setting 7- Tests applied to the cement industry: 3. Magnesium oxide percentage (MgO %) : It is done on limestone This percentage should not exceed 5% Dolomite ?? (CaCo3.MgCo3) Because its increase means that the CaO + MgO quality of limestone is poor. Magnesium oxide does not take part in the cement reactions. 7- Tests applied to the cement industry: 4. Powder size: It should be very fine, such that at least 98% of it should pass through mesh 200 (200 pinch per linear inch). 7- Tests applied to the cement industry: 5. Setting time : The aim is to test the speed of cement solidification. Samples of cement are mixed with standard amount of water ,then measure the time at which a standard needle with a standard weigh cannot penetrate the prepared sample. 7- Tests applied to the cement industry: 6. Volatile materials percentage: The percent should not exceed 5% ?? because the increase of this percentage is an indication of the presence of some humidity in the cement before usage and thus its quality is low. 7- Tests applied to the cement industry: 7. Sulpher trioxide percentage (So3 ): The percent should not exceed 3.5% (equivalent to gypsum (CaSo4)%= 6.5%) (Gypsum) CaSo4.2H2o ?? because the increase of gypsum content retards the solidification process. 8- Other types of cement : 1. Rapid hardening Portland cement : It contains high percentage of tricalcium silicate (C3S) which causes rapid solidification. This cement is also very fine, such that not less than 99.5% of it pass through mesh 320, to increase the surface area exposed to water during mixing and enhance the reactions speed. 8- Other types of cement : 2. Iron slag cement : consists of iron slag + OPC. Furnace slag contains the three main components found in the Portland cement but with different percentages Lower in quality than OPC as the furnace slag is in the form of bulk masses which cannot be grinded or converted to fine powder, compared with the clinker which is in the form of easily grinded porous balls. cannot solidify perfectly. it is not preferable to be used in the reinforced concrete mortar. 8- Other types of cement : 3. Chemical resistant cement : Solid material in the form of pellets Liquid mixture E.X: Fine sand or E.X: phenol + graphite or asbestos + formaldehyde Resin product Used when the building are subjected to chemicals, a special type of cement is used to cohere its components or coat them. E.X: Carbolic cement. 4. Sea water resistant cement : Seawater resistant cement, also known as marine cement, is a type of cement that is specifically designed to withstand the exposure to seawater. Seawater contains high concentrations of salts, such as chloride ions, which can penetrate the cement matrix and initiate corrosion of the steel reinforcement within concrete structures. Seawater resistant cement addresses this issue by incorporating certain additives or modifying the cement composition to enhance its resistance to chloride attack. There are several types of seawater resistant cement available, each with its own specific formulation and properties. Some common types include:  Sulphate-Resistant Calcium Magnesium Blended cements Portland Cement: Aluminate Cement: phosphate Cement such as Portland Pozzolana Cement: SRPC is blended with CAC is an MPC is a type of PPC can also exhibit a higher proportion of alternative to cement that improved resistance to C3A and a lower ordinary Portland utilizes chloride attack amount of C3S. cement, OPC that magnesium compared to OPC. contains a high phosphate This composition proportion of compounds as These cements reduces the calcium aluminate binders instead of incorporate permeability of the compounds. traditional calcium supplementary cement matrix and – based binders. cementitious materials makes it more These compounds like slag , silica fumes resistant to sulphate provide better It offers excellent or fly ash, which and chloride attack. resistance to resistance to enhance their chloride chloride attack, durability in penetration and making it suitable aggressive can be used in for marine environments. marine applications.