| Spontaneous combustion gangue aggregate with better quality, larger reserves, easy mining, the characteristics of low price, occupies a place in the family of light aggregate. But with the widely application of the premixed concrete and because of spontaneous combustion gangue aggregate’s large porosity, high water absorption, it will absorb the mixing water so that make mixture too thick and the slump value small. In addition, the research on concrete durability of spontaneous combustion gangue aggregate mixture is less. This paper is the National Natural Science fund committee and Shen Hua group co. LTD. jointly funded projects "Research on key scientific problem of Coal gangue in cement and concrete utilization"(U 1261122). By taking on the pretreatment of coal gangue sand aggregate, mixed mineral admixture and other technical way to achieve the goal of preparation of large liquidity, high durability coal gangue sand concrete, and develop the theory of concrete, provide a reference for practical engineering application. The research results as follows:(1)The coal gangue sand by mechanical broken has poor grading. Through a combination of natural sand in different proportion, it can meet the quality requirements of the fine aggregate in concrete;(2)By means of the coal gangue sand pretreatment, mixed with high efficiency water reducing agent and mixed mineral admixture, when the coal gangue sand all replace natural sand, can realize to make a big flow, medium strength, high durability of the coal gangue sand concrete goals;(3)When the additional water of coal gangue sand is 60% bibulous rate, and mixing the premise in the ten minutes pre-wetting, concrete mixture can achieve large liquidity demands of ready-mixed concrete and hardening strength grade can meet the requirements of structural design;(4)The orthogonal experiment of medium sthength coal gangue sand concrete shows that gelled material mass ratio is the most significant influence on concrete mixture slump; the mass ratio between admixture on mixture slump is not significant. When cement:fly ash:slag=80:10:10, water reducing agent:air-entraining agent=0.8:0.2, the mixture can achieve the biggest slump in guarantee under the premise of good adhesiveness and water retention; the mass ratio between admixture and gelled material mass ratio of the influence on 28d compressive strength of concrete are obvious, and the mass ratio between admixture is more significant than the gelled material mass ratio. When cement:fly ash: slag=80:10:10, water reducing agent:air-entraining agent=1:0, concrete achieves the highest strength;(5)The chloride ion penetration resistance and freeze resistance test of the coal gangue sand concrete shows that the mass ratio between admixture on the coal gangue sand concrete resistance to chloride ion penetration performance is particularly remarkable, the gelled material mass ratio had no obvious effect on the chloride ion penetration; when the freeze-thaw cycles within the 100 times, two factors had no influence on it; when freeze-thaw cycles is more than 150 times, the gelled material mass ratio gradually obvious influence on performance of freezing and thawing. |
