(Continued)
Sustainability has been regarded as an important evaluation index for the long-term existence and sustainable development of industrial products in the world. Nowadays, the sustainability and green degree of products have become synonymous in a sense, because sustainable products must be green.
Impact of raw materials on product sustainability
Cementitious materials
Compared with non autoclaved fiber cement board, the cementitious material consumption of calcium silicate board and fiber cement board is only about 40% of the former, which belongs to low carbon building materials products.
Calcium silicate board manufacturers at home and abroad generally use hydrated lime as cementitious material, or mainly use hydrated lime with appropriate amount of ordinary portland cement.
The cementitious material used in the manufacture of fiber cement board is ordinary portland cement. In order to reduce the amount of clinker in cement as much as possible. It is suggested to use composite Portland cement instead of ordinary portland cement.
China’s Composite Portland cement contains Portland cement clinker, two or more kinds of admixture and appropriate amount of gypsum. The total content of admixture is more than 15%, but not more than 50%. The technical requirements of this kind of cement are basically the same as ordinary portland cement.
Because the composite cement is mixed with different admixtures, it is better to choose which kind of composite cement to make fiber cement board. It is better to conduct necessary tests on the process line first.
Siliceous material
In order to make calcium silicate board or autoclaved fiber cement board, adding siliceous materials into raw materials. The effect is that calcium materials react with siliceous materials to form tobermorite crystals in the process of autoclave.
For a long time, foreign enterprises have used ground quartz sand as silica material in the manufacture of such boards, mainly because of its high SiO2 content (up to 90%).
In the late 1990s in China, some enterprises producing autoclaved fiber cement board have replaced all ground quartz sand with fly ash. And the product quality can meet the standard requirements.
In recent years, some foreign fiber cement board enterprises have replaced part or all of the ground quartz sand with fly ash.
The use of fly ash instead of ground quartz sand not only makes use of industrial waste, but also avoids the energy consumption of grinding quartz sand and reduces the product cost. However, the chemical composition and radioactive content of fly ash should be required. Low calcium fly ash with SiO2 content no less than 50% should be used. In order to protect the environment and protect human health. The radioactive content of the fly ash used should not exceed the limit specified in the national standard “limits on radioactive substances in industrial waste residue for building materials”.
Admixtures
Some enterprises at home and abroad add a small amount of micro silica powder (about 4%) in the manufacture of autoclaved fiber cement board or calcium silicate board. Because the content of amorphous and highly active SiO2 in the micro silica powder can reach more than 95%. The amount of siliceous material can be appropriately reduced. And the bonding of thin material layer in the molding process and the formation of tobermorite crystal in the autoclaved process can be promoted.
When making calcium silicate board with high fire resistance, it is necessary to add some special admixtures, such as acicular wollastonite, expanded perlite, expanded vermiculite and mica scale.
The domestic and foreign enterprises that produce this kind of board all use the non hardened waste slab and the cutting edge material in the production process to make slurry and reuse it. The vast majority of enterprises use the scrap, debris and fine particles produced in the process of board after processing as admixtures after collection and grinding. The amount of blending in the products can reach more than 10%, which is of great significance to reduce the pollution around the production area.
Sinopower Industries Group Limited can supply you high quality fiber cement board /calcium silicate board production line machinery. Welcome to visit our factory and working site.
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Post time: Sep-03-2020