(火山灰水泥)PPT课件

- usu. generating less heat at a slower rate than Type I
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Portland Ceres of considerable mass, such as large piers, heavy abutments, and heavy retaining walls, especially when the concrete is placed in warm weather.
-used where precaution against moderate sulfate attack is important, as in drainage structures where sulfate concentrations in groundwaters are higher than normal but not unusually severe
(7) Discharging the clinker red-hot from the lower
end of the kiln and then transferring it to various
types of coolers to lower the clinker to handling
Type V: sulfate-resisting, used only in concrete structures that will be exposed to severe sulfate action, principally where concrete is exposed to soil and groundwater with a high sulfate content.
5. Portland cement: common calcium silicate cement
II. *Portland Cements
1. History: In 1824, Aspdin, a British stone mason, invented a cement which he named portland cement because it resembled a stone quarried on the Isle of Portland off the British Coast.
Type IA: similar to Type I with the addition of airentraining properties only
Type II: generating less heat at a slower rate and with a moderate resistance to sulfate attack
Type I: a normal, general-purpose cement suitable for all uses
- used where the special properties of other types are not required;
- used where cement or concrete is not subject to specific
(9) Packing and storing the gray powder—portland cement
5. Types of Portland Cements
According to AASHTO and ASTM specifications, eight types of portland cements are listed as follows:
temperatures;
1.
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Portland Cements
(8) Combining the clinker with gypsum and grinding the mixture to pass through a No. 200 mesh sieve;
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Portland Cements
II. Portland Cements 4. Manufacturing Process: 2) Breakdown process (1) obtaining raw materials which are reduced by
primary and secondary crushers to 5-inch size (125-mm), then to 3/4-inch(19 mm); (2) proportioning the materials at the cement plant to create a cement with a specific chemical composition with two different methods, dry and wet; (3) Completing the grinding and blending operations for the materials in slurry form;
Type IIA: identical to Type II with the addition of air-entraining properties
Type III: a high-early-strength cement, chemically and physically similar to Type I, except that its particles have been ground finer.
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4. *Manufacturing Process:
1) Producing a cement that meets specific chemical and physical specifications requires careful control of the manufacturing process.
Portland Cements
I. Types of Cements 1. pozzolana and pozzolanic cements (火山灰水泥） 2. blastfurnace slag cements （炉渣水泥） 3. high-alumina cements (高矾土水泥）
4. special cements such as white, colored, waterproofed, masonry, oil-well, and expansive cements
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Portland Cements
Type IIIA: an air-entraining, high-early-strength cement
Type IV: with a low heat of hydration and developing strength at a slower rate than other cement types, making it ideal for use in dams and other massive concrete structures where there is little chance for heat to escape
3. Constituents: tricalcium silicate(3CaO•SiO2 or C3S), dicalcium silicate (2CaO•SiO2 or C2S), tricalcium aluminate (3CaO•Al2O3 or C3A), and tetracalcium alumino ferrite(4CaO•Al2O3•Fe2O3or C4 AF)
exposures, such as sulfate attack, or to an
objectionable temperature rise due to heat generated
by hydration.
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Portland Cements
-uses including pavements and sidewalks, reinforced concrete buildings, bridges, railway structures, tanks, reservoirs, culverts, sewers, water pipes and masonry units
2.
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Portland Cements
II. Portland Cements
2. Raw and processed materials: calcareous materials like limestone and marl and argillaceous substances like clay and shale, with major mineral ingredients of calcium, silicon, aluminum, and iron.
-providing high strengths at an early period, usually a week or less
-used when forms are to be removed as soon as possible, or when the structure must be put into service quickly, especially in cold weather.
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Portland Cements
6. Tests on specifications of cement 1) Chemical test: a chemical analysis of the proper
quantity of strength-giving compounds; 2) Physical test: fineness, stability, time of set, air
(5) forcing burning fuel consisting of powdered coal or natural gas into the lower end of the kiln;
(6) heating the raw materials to very high temperature, and at 2700ºF (1480ºC), a series of chemical reactions causing the materials to fuse and creating cement clinker—grayish-black pellets, often the size of marbles;
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Portland Cements
(4) after blending, feeding the mixture of raw materials into the upper end of a tilted rotating, cylindrical kiln;
content, and compressive strengths of mortars made using Ottawa sand
3) III. Homework 1. The manufacturing process of Portland cement. 2. Ex. IV on page 43 in the main text book.