Anti-crack performance of concrete with phosphorus slag and fly ash singly and compositely added is investigated in terms of physical performance, hydration heat, dry shrinkage and creep. Index K is introduced to evaluate the crack resistance of phosphorus slag concrete. Results show that the strength of phosphorus slag concrete increases with the increase of fineness, and when surface specific area is greater than 300 m 2 /kg, the tendency slows down. Strength decreases with phosphorus slag content increasing and there is an optimal content existing between 30% and 50%. Both phosphorus slag and fly ash have obvious effect on elongating time setting, reducing hydration heat to a large extent and increasing creep value. Crack resistance of phosphorus slag concrete is divided into three stages, namely early hazardous stage, growth stage and later mature stage. With microstructure analysis, mechanism of effect of phosphorus slag on concrete performances and P and F on cement hydration is explored. It is concluded after comprehensive evaluation that the crack resistance of phosphorus slag concrete is approximate to, even to some extent better than that of fly ash concrete.

Hydration characteristics of Portland cement paste with phosphorus slag powder incorporated and hydration kinetics was investigated with SEM, X-ray diffraction, DTA-TG and calorimeter Ⅱ80. Results showed that phosphorus slag powder could reduce total amount of hydration products yet had little influence on the type of hydration products. The total amount of heat of hydration was decreased by 49.11% and the final setting was postponed by 2.28 h when phosphorus slag powder substituted 35% Portland cement by mass. The accelerating stage of this composite paste was controlled by catalysis, decreasing stage controlled by both catalysis and diffusion while stabilizing stage by diffusion alone. Hydration resistance and activation energy were reduced and hydration speed was accelerated.

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The advanced temperature and stress test machine was introduced to determine the early cracking tendency of concrete with inclusion of light-burnt MgO under full restraint by tracking the development of thermal, physical and deformation properties. Results showed that light-burnt MgO being incorporated ranging between 4 wt% and 6 wt% of cementitious materials was beneficial to increase the maximum compressive stress and cracking stress of concrete by 0.37 MPa and 0.2 MPa on average respectively. The second zero stress temperature was reduced by 11.4 ℃ and the maximum temperature was slightly reduced while cracking thermal impact was signifi cantly enhanced from 59.8 ℃ to 66.2 ℃. Sensitive anti-cracking coeffi cient F was forwarded to assess the early cracking tendency of concrete and the inclusion of 4 wt% lightburnt MgO with activity of 109 s ranked the best in crack resistance.