Research On Anti-Permeability And Frost Resistance Of Concrete Whose Coarse Aggregate Is Replaced By Coal Gangue

Coal gangue is one of trash produced in coal industry, each year it produces a lot of coal gangue, which causes severe pollution to environment. The unreasonable use of coal gangue will lead to enormous loss of society, economy and environment. The production of aggregate to mix cement concrete with coal gangue can reduce the dosage of natural aggregate in civil engineering and have good economic and social benefits. This paper concluded the range of reasonable amount of the gravel substituted by gangue adopting the single factor method and optional experiment design through preparing concrete which the coarse aggregate is gangue substituting the gravel, the test used compressive strength, anti-permeability and frost resistance as evaluation indexes, and it researched the effect regular of anti-permeability and frost resistance of the concrete influenced by all variables including the amount of coal gangue, the water-binder rations, the amount of the fly ash and the type and amount of admixtures, and make a comparison with the ordinary concrete. The experimental resultsshowed that:(1)By comparison the fundamental physical properties of coal gangue and general gravel, we can know that the interspaces rate of coal gangue, ratio of water content, ratio of water absorption, soil content, crush indicators are larger.we should take overall consideration of workability and mechanical property of the mixture of coal gangue and concrete thereby to make sure the limits of reasonable dosage that coal gangue substitute for gravel should within 60%.(2) Under the standard mix proportion, with the increasing in the amount of coal gangue to replace the coarse aggregate from 0 to 60%, thecompressive strength,anti-permeabilityand frost resistance of concrete reduced in different degree, the compressive strength of 28 d decreased from 55.7MPa to 40.8MPa, the pressure of permeability decreased from 1.3MPa to 0.9MPa,the number of freezing and thawingdecreased from more than 300 times to less than 150 times, the best dosage of coal gangue is about 40%; Increasing the water-binder ration from 0.35 to 0.45, the pressure of permeability decreased from 1.3MPa to 0.7MPa,the number of freezing and thawing decreased from more than 300 times to about 100 times, it can make sure that water-binder ration which meet C40 concrete be not more than 0.4; When using the fly ash as an additive, the best content was about 10%, the pressure of permeability can reached 1.2MPa, the number of freezing and thawing can reached 300 times;while the impermeability and frost resistance will decline obviously if the content is more than 20%; The use of water-reducing agent and air-entraining agentimproved the anti-permeability and frost resistance of concrete significantly. As a result,the contentof water-reducing agent was about 0.5% and the contentofair-entraining agent was about 0.02% of cementing materials, both pressure can reached 1.1MPa and both cycle times can reached 300;If two admixtures have a compound use, the effect will be better than only one, the pressure of permeability can reached 1.3MPa and the number of freezing and thawing can reached 350 times.(3) With the use of mineral additives and admixtures could improve the pore structure of the concrete, after freezing and thawing cycles,the degradation rate of pore structuregot slow significantly.Compare 300 times before and after freezing and thawing, the increasing percentage of the total pore volume of the concretemixed with fly ash decreased from 12.6% to 9.2%, and its best dosage was about 10%; the increasing percentage of the total pore volume of the concretethat composite using water-reducing agent and air-entraining agent decreased from 12.8% to 5.7%, the best dosage was 0.4% and 0.02%.