Reaction Degree Of Fly Ash And Blast Furnace Slag In Cement Pastes

Fly ash and blast furnace slag have become absolutely necessarily binding materials in cement industry. To make sure the reaction degree of fly ash and blast furnace slag in cement pastes is very important. It is significant in evaluating the reactive activity of fly ash and blast furnace slag ,estimating the contribution to the structure, researching the reactive kinetics. The quality of fly ash varies in a big range. It is vital to select typical fly ash and research the relationship among the reaction degree, constitute and particle size distribution of fly ash.In this dissertation, typical fly ash and slag were selected and the reaction degree of fly ash and blast furnace slag were measured by selective solution method at first. Then, the relationship between reaction degree of fly ash or blast furnace slag in cement pastes and specific surface area of fly ash or blast furnace slag, replacement ratio of fly ash or blast furnace slag at different ages were constructed. Correlation among reaction degree, reaction depth and particle size distribution parameter were established. The relationship between Ca(OH)2 reduction content in cement pastes and reaction degree of fly ash and blast furnace slag and the relationship between strength and reaction degree of fly ash and blast furnace slag were also researched. Lastly, the contribution of every grinding energy cost to reaction degree and strength were analyzed.The results showed that the reaction degree of fly ash or blast furnace slag has good power function correlation with specific surface area of fly ash or blast furnace slag, replacement ratio of fly ash or blast furnace slag and ages. The sequence of reaction degree of different fly ashes were: median calcium type>high calcium type>low calcium with high aluminum type>low calcium with median aluminum type (7d,28d);and low calcium with high aluminum> median calcium type> high calcium type>low calcium with median aluminum type(90d). The proposed specific surface area of fly ash and slag for good reaction degree were: 600±10m2/kg for low calcium high aluminum type fly ash; median calcium type,600±10m2/kg(90d or before it), 500±10m2/kg(180d);low calcium median calcium type, 700±10 m2/kg(28d or before it),500±10 m2/kg(90d);slag, 500±10m2/kg.When the replacement ratio of fly ash or blast furnace slag is 50% and the ratio of water to binding materials is 0.5, reaction degree of fly ash or blast furnace slag has negative correlation with particle size distribution characteristic parameter. Of all the characteristic parameter, the correlation between reaction degree and surface area mean particle size is best. Reaction degree of fly ash or blast furnace slag has good liner correlation with surface area mean particle size. Compressive strength of cement pastes has good logarithmic correlation with reaction degree of fly ash or blast furnace slag. So, surface area mean particle size can be good quality control parameter for fly ash or blast furnace slag. Surface area mean particle size has the trait of both particle size distribution and special surface area,it is more scientific than sieve residue or specific surface area as quality control parameter for fly ash or blast furnace slag.Based on the particle size distribution parameter of fly ash or blast furnace slag, reaction depth of it can be deduced from reaction degree of it. The sequence of reaction depth of different fly ashes were: high calcium type> median calcium type>low calcium with median aluminum type >low calcium with high aluminum type (7d), and median calcium type> high calcium type>low calcium with high aluminum> low calcium with median aluminum type(28d,90d).The increase of specific surface area of fly ash has positive liner correlation with the increase of grinding time. The increase of specific surface area of blast furnace slag has positive logarithmic correlation with the increase of grinding time. With the increase of specific surface area for fly ash or blast furnace slag, the particle equality coefficient increase and characteristic particle size decrease. When the specific surface area add to 600m2/kg,the equality coefficient begin to drop or stabilize.When the replacement ratio of fly ash or blast furnace slag is 50% and the ratio of water to binding materials is 0.5, Ca(OH)2 reduction content in cement pastes have good liner correlation with reaction degree of fly ash, Ca(OH)2 reduction content in cement pastes have no good relation with reaction degree of blast furnace slag.From the contribution of grinding energy to reaction degree of fly ash or blast furnace slag, the proposed specific surface area of fly ash and blast furnace slag were: low calcium high aluminum type fly ash , 600±10m2/kg(1d,3d), 700±10m2/kg (7d,14d,28d, 60d,90d,180d) ; median calcium type,600±10m2/kg(90d or before it), 500±10m2/kg(180d);low calcium median aluminum type, 600±10 m2/kg(3d), 700±10 m2/kg(7d,28d),500±10 m2/kg(90d);blast furnace slag, 500±10m2/kg.