The Distribute Characteristic Of Slag Powder And The Influence On Strength Of Cement

Hardened cement paste is a tri-phase system consisted of gas, liquid and solid with holes. Porosity of hardened cement paste has an important factor affecting its strength. For resulting in cement stone of low porosity and high strength, three possible mechanisms are suggested and explored by the author. Based on the original packing state of cement particles and the micro-structure of hydrate products, it may suggest that the densest packing, the speediest hydrate rate, and the combination of the packing states and hydrate rate mentioned are essential for desired cement stone.Slag powders of seven finenesses, a clinker powder and a gypsum powder are prepared by a ball mill. The size distributions of the powders are measured to be accordance with the RRSB distribution and the values of n for each of the powders have a narrow range. The difference slag powders are characterized by granularity parameters such as de, d50, d90 and the values of n. Comparing the distribution of slag powder and clinker powder with Fuller curve of the dense packing, it shows that the content of fine particles used in specimen is less require for the Fuller curve. The curve of higher specific surface area is more closed to Fuller curve.The size distribution of slag cement, containing 10~70% of slag powder and 4% of gypsum, is also accordance with the RRSB distribution. The values of n of slag cement, consisted of slag powder with specific surface area less than 441m2/kg and clinker powder with specific surface area of 356m2/kg, increases with the content of slag increasing. For slag powder's specific surface area larger than 500m2/kg, its n value decreases with the content of slag increasing in a certain content of slag. The decreasing slope increases with specific surface area of slag augmenting. The value of de and d50 of six kinds slag powders are less than those of clinker. The values of de and d50 of slagcements decrease lineally with the content of slag increasing. The higher the fineness ofslag, the larger the slope of value of de and d50.It is proven than the strength of slag cement is accordance with the characteristic parameters of particle size distribution of slag. The strength is characterized by the ratio of the same ages' strength of slag cement and the standard sample, Portland cement. The fineness characteristic parameter is specific surface area of slag powder. The specific surface area of slag powder from 344 to 414m2/kg, from 441 to 549m2/kg and from 603 to 640m2/kg, its ratios of flexure and compressive strength of 3d show decreasing, fluctuant and increasing trend respectively with the content of slag powder increasing. The ratios of compressive strength of 7d and 28d have the same trend as that of 3d. The ratios of flexure strength of 7d show fluctuant with the content of slag increasing with specific surface area between 344 and 414m2/kg. The ratios of flexure strength of 7d is increasing with the content of slag increasing with specific surface area larger than 414m2/kg, so does the ratios of flexure strength of 28d with specific surface area of slag larger than 344m2/kg.Setting the content of slag and specific surface area as X coordinate and Y coordinate respectively, the contour maps of the ratios of slag cement strength are depicted. The center of the tiptop compressive strength ratios moves from 60% to 48% with ages increasing, while the center of the tiptop flexure strength ratios moves to 70% with ages increasing.The polydisperse distribution is simplified to mono-disperse distribution. The granularity is characterized by the value of d50. Setting d50 of slag cement as X coordinate and the ratios of d50 of slag powder and d50 of clinker powder as Y coordinate, the contour maps of the ratios of slag cement strength is depicted. The minimum strength ratios of flexure and compressive strength of 3d occur at X of 14~16.5 m and Y of 0.85~1.0 and those of 28d occur at X of 9~14 m and Y of 0.85~ 1.1. All the Y values are about 1.0 and this corresponds to the packing model of two kinds of...