| Infrastructure construction in China has experienced decades of fast development and will soon transform to large-scale maintenance period. The current rapid repairing materials are mainly cement concrete rapid repairing materials, special cement, organic-inorganic compound repairing concrete etc. But there are issues that organic type of repair materials are expensive, uneven strength and deformation. Traditional Portland cement production is a huge energy consumption and the consumption of non-renewable resources. Using organic type of repair materials and the preparation of rapid repair concrete with Portland cement is not conducive to go green and sustainable development. Therefore, study on phosphorous slag-based cementitious material with high early strength and properties of the concrete can shorten the maintenance period of infrastructure and prolong its service life, which has high economic benefit and social benefit. On the other hand, phosphorus slag is industrial wastes generated by electric heating method in production of yellow phosphorus. Graining phosphorous slag is made by water quench cooling with molten phosphorous slag, of which content of vitreous body structure can reach more than 90%. Graining phosphorous slag has the potential activity of gelation, which can be used for the preparation of new repair material. However, because AI2O3 content in phosphorus slag is less, its early activity is low. Containing a certain amount of P2O5, which has retarding action Portland cement, Graining phosphorous slag will affect the early strength the of cement base material. It is not conducive to rapid hardening and early strength of repair materials.To solve above problems, this paper is that a new repair materials is studied with phosphorus slag as main raw material, supplemented by graphite tailings and other materials. Through the research of active excitation of the phosphorus slag and using composite material technology, phosphorous slag-based cementitious material with high early strength is developed. Through research on composition and hydration hardening microstructure-performance of gelled material, its hydration hardening process and microstructure characteristics are discussed. On this basis, the design and preparation of phosphorus slag concrete C30, C40 and C50 is developed. Performance of frost resistance and resistance to sulfate erosion and volume deformation about the concrete is experimental studied. In this paper, the main work and achieved important results are as follows:l)Through gelling property of phosphorus slag powder and its relationship with the particle size distribution, phosphorus slag powder should reach a certain fineness requirement, which improve the activity of phosphorus slag powder. Under this study test conditions, the specific surface area of the phosphorus slag powder should be not less than 397 m2/kg. At the same time, the content should be as far as possible increased on the gelation properties in the promoting role of particles, which the particle size is 5.0-30.2 microns, especially content of particles (size 5.0-20.0 microns) playing a key role. The content of particle (> 30.2 microns particles) should be limited and reduced. The gelling property of phosphorous slag is improved by optimizing the phosphorus slag powder particle size distribution and facilitate the preparation of phosphorous slag-based cementitious material with high early strength.2) Phosphorous slag-based cementitious material with high early strength is developed with phosphorus slag as the main components, supplemented by graphite tail mineral powder and a small amount of Portland cement and silica fume mineral materials. Its proportion is that phosphorus slag powder:graphite ore tail:Portland cement:mineral materials A:silica fume is (0.78-0.81):0.05:0.09:0.05:(0-0.03). At the same time, the 1.4 modulus of sodium silicate as the alkali-activator (in Na2O,5%, accounting for the total quality of the gelled material), retarder K (1%), the developed mortar specimens of phosphorus slag cementing material are that 1 d,3 d and 28 d compressive strength were 16.1 MPa,27.2 MPa and 49.6 MPa and 1 d,3 d and 28 d flexural strength were 3.5 MPa, 5.1 MPa and 11.5 MPa. It accords with GB175-2007 requirement towards the intensity of the P.O 42.5R.3) XRD, IR, SEM and TG-DTG microscopic test results show that Phosphorous slag-based cementitious material with high early strength has early hydration. In the age of 12h hydration degree can reach 60% of 28d hydration degree. In the early hydration a large number of analcime and hydrated calcium silicate gel is generated, but product of Ca(OH)2, such as crystal, is very little. Doped graphite tail mineral powder, etc. can have further consumption of Ca(OH)2. In the hardening body, no hydration product particles and a small amount of crystal is closely covered by gel product, which makes its microscopic structure compact. This is why the phosphorus slag cementing material microscopic mechanism with high early strength.4) The design and preparation of phosphorus slag concrete C30, C40 and C50 is developed by phosphorous slag-based cementitious material with high early strength. The basic mechanical performance of concrete is studied. According to the test results obtained the relationship between its water/cement ratio and the concrete compressive strength is applicable, which is known as bao’s formula.α is 0.48, and β is 0.085. The formula provides the basis of the mixture ratio design of the phosphorus slag concrete on engineering.5) The shrinkage, the frost resistance, resistance to sulfate erosion and water corrosion resistance and other long-term performance and durability of phosphorus slag cementing concrete is researched. It shows that the prepared phosphorus slag based concrete by 28 air-dried shrinkage rate was 0.08%, meeting the anticipated goal of 0.1% or less. The concrete after soaking in water, its strength can still stable growth, which means its water corrosion resistance performance is good. Frost resistance and resistance to sulfate erosion of phosphorus slag based concrete are superior to the same strength grade of Portland cement concrete. |
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