Portland cement for the of asbestos cement products
The use of Portland cement in the production of the OCA asbestos is characterized by several features. In the manufacture of asbestos cement initial hydration proceeds at a very high water-cement ratio, and in the production of highly water-cut asbestos cement mass is filtered, sucked and squeezed a large amount of water.
Cement particles must be thin enough to stay on asbestos fibers, however, their excessive dispersion can cause increased water demand of the binder has a negative effect on the dewatering and compaction of the product. Therefore portland GOST 9835-77 should have fineness characterized by a specific surface area no less than 2200 and not more than 3200 cm2 / g
This cement clinker should contain (%): C3S not less than 52 and not less than NWA 3N not more than 8. SaOslob content no more than 1, a MgO - 5%.
To intensify the clinker grinding allowed supplementation does not impair the quality of the cement in an amount of not more than 0.5% by weight of cement. Initial setting time of cement should occur no earlier than 1.5 hours, and the end - no later than 10 hours from the start of mixing.
Portland cement for the production of asbestos cement products are divided into grade 400 and 500, determined on samples of a solution of 1: 3 to GOST 310.1-76 (as amended.) - GOST 310.4-81.
Portland cement for the production of asbestos cement products is characterized by essentially the same construction properties as ordinary Portland cement, and differs from it more intense hardening and increased strength at initial stages.