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14.1 The cement shall be stored in such a manner as to permit easy access for proper inspection and identification of each shipment, and in a suitable weather-tight building that will protect the cement from dampness and minimize warehouse set.
15. Manufacturer’s certification
15.1 Upon request of the purchaser in the contract or order, a manufacturer’s report shall be furnished at the time of shipment stating the results of tests made on samples of the material taken during production or transfer and certifying that the cement conforms to applicable requirements of this specification.
As previously noted, emissions guidelines for cement kilns vary from country to country. The sample country discussed in this case is Canada.
Extracts from “Development of CCME National Emission Guidelines for Cement Kilns”*
The guideline proposes emission limits for new kilns in the cement manufacturing industry, and makes some recommendations on emission reductions from existing plants that are being modified or upgraded. Regional or provincial regulatory authorities could decide to impose stricter standards in response to local air-quality problems.
The guideline was prepared through extensive consultation between industry, governments, and environmental groups. Principles that were considered to be important were those of pollution prevention, energy efficiency, cost-effectiveness, and a comprehensive view toward minimizing various emissions to reduce air pollution and greenhouse gases. A future guideline for lime kilns will also be developed subsequent to further research with the lime industry. Tables C-5 through C-7 describe characteristics of cement.
Cement kilns in the sample country (Canada)
Portland cement is mixed with sand, aggregates, and water to form the basic building material known as concrete. The production of cement, which comprises 10-15 percent of the final concrete mixture, is based on the conversion (pyroprocessing) of a mixture of limestone (CaCO3) and shale or clay, into clinker material consisting of compounds of calcium oxide (CaO), by the addition of large quantities of heat in a coal- or gas-fired rotary kiln (Fig. C-18). The raw cement clinker exits the kiln and is usually mixed with 3 to 6 percent gypsum and then finely ground into powder. Sometimes it can also be mixed with flyash or other cementitious additives if blended cements are used. The characteristics of the raw feed materials, the finished product, and the resulting emissions are very site-
* Source: Environment Canada. Adapted with permission.
Cement; Portland Cement C-29
FIG. C-18 Basic schematic of cement production. (Source: Environment Canada.)
TABLE C-8 Optional Physical RequirementsA
Cement Type I IA II IIA III IIIA IV V
False set, final penetration, min, % 50 50 50 50 50 50 50 50
Heat of hydration:
7 days, max, kJ/kg (cal/g) --- --- 290 (70)B 290 (70)B --- --- 250 (80)C ---
28 days, max, kJ/kg (cal/g) --- --- --- --- --- --- 290 (70)C ---
Strength, not less than the values shown:
Compressive strength, MPa (psi)
28 days 28.0 22.0 28.0 22.0
(4,060) (3,190) (4,060) (3,190)
Sulfate resistance,D 14 days, max, % expansion --- --- --- --- --- --- --- 0.040
A These optional requirements apply only if specifically requested. Availability should be verified. See Note 1 in section 4.
B The optional limit for the sum of the tricalcium silicate and tricalcium aluminate in Table C-6 shall not be requested when this optional limit is requested. These strength requirements apply when either heat of hydration or the sum of tricalcium silicate and tricalcium aluminate requirements are requested.
C When the heat of hydration limit is specified, it shall be instead of the limits of C3S, C2S, and C3A listed in Table C-5.
D When the sulfate resistance is specified, it shall be instead of the limits of C3A and C4AF + 2C3A listed in Table C-5.
specific depending upon the chemistry of the quarried limestone, the type of cement required, and the type of kiln used. See Tables C-5 through C-8.