Application of good limestone source in concrete
With the economic development, the construction scale continues to expand, and qualified natural building materials are gradually exhausted, especially river sand with large consumption and common mineral admixtures, such as fly ash and slag, which increase rapidly with the popularity of ready mixed concrete. While the gravel plant produces a large number of stones less than 5 nlm in the production of gravel, if not effectively utilized, not only the good source of limestone will be wasted, but also a large amount of cultivated land will be occupied, It will affect the local ecological environment. In view of the good source environment, the limestone good source crushing is carried out to form crushed stone, machine-made sand and limestone powder to overcome the local construction dilemma of lacking sufficient river sand and qualified fly ash, realizing the pollution-free application of limestone good source in concrete and conforming to the energy-saving and emission reduction policy.
Crushed stone, machine-made sand and limestone powder for building are prepared by crushing, sieving, washing and grinding with limestone good source containing more than 87% CaCO as raw material. By controlling the size of the sieve mesh, crushed stone with different particle sizes can be prepared; Adjust the flow of screen and water washing to keep the content of prepared stone powder at about 3%. The machine-made sand passing 0.315 sieve mesh shall not be less than 15%, conforming to Zone 2, and the fineness modulus is 2.6; The percentage of residue on the 45 tun square hole sieve of limestone powder obtained by grinding is 4.6%.
In view of the building dilemma of the increasing shortage of river sand and fly ash, the research on the application of crushed stone, machine-made sand and limestone powder, which are good sources of limestone in concrete, can provide sufficient concrete for the construction of local urban areas, improve the quality of concrete, and improve its green degree and application technology level.
Fly ash quality is not stable, sometimes not up to the Ⅱ standard, the price is about 128 yuan /t, limestone powder according to 20% to replace cement, per cubic meter of concrete can save about 8 yuan; Machine-made sand is about 15 yuan cheaper than river sand per ton, and about 12 yuan can be saved per cubic meter of concrete. Every year according to 500,000 cubic meters of pumped concrete, can save the project cost of more than 10 million yuan. In addition, the indirect economic benefits are significant by saving the cost of transferring materials from the field and reducing the cost of repairing quality defects caused by material fluctuations.
In view of the construction difficulties, combined with the good natural environment, the research on the application of crushed stone, machine-made sand and limestone powder formed by the good source of limestone to replace river sand and fly ash in concrete has been carried out, which not only protects the ecological environment, realizes the greater application of limestone in concrete and expands and improves the application technology level of concrete. The engineering practice shows that compared with ordinary ready mixed concrete, this kind of concrete has better quality, strong controllability, higher comprehensive benefit and great development potential, which has a good inspiration and reference for developing the ready mixed concrete market.