The objective of this paper is to investigate the effect of the combined use of organic fiber and shrinkage reducing admixtures on the engineering properties and fire endurance performance of the high strength concrete with 50 MPa. Polylon fiber, which was mixed with nylon fiber and polypropylene fiber was applied to achieve spalling prevention performance. Two different shrinkage reducing agents were also used such as emulsified refined cooking oil (ERCO) and glycol based shrinkage reducing agent to reduce autogenous shrinkage. Fire resistance test was conducted in accordance with ISO-834 curve using cylindrical specimen with 100 mm in diameter and 200 mm in length for three hours. The following results could be made as conclusion.

(1)For the fundamental properties of fresh concrete, for all the different types of concrete with different W/B, comparing with Plain concrete, slump and flow were little decreased and showed similar flowability with Plain concrete. For the segregation resistance test, for all types of concrete with different W/B, the evaluation index for segregation (EIS) is lower than 2.5 which belongs to level 2. It is considered that all types of concrete with different addition ratio of ERCO showed good workability.

(2) For the air content, All types satisfied the target range of 2±1 % and as the adding ERCO''s hydrophobic group could be combined with AE component, so the air content was largely reduced. For the high strength concrete, comparing with normal strength concrete, it always with more compact structure which have high resistance for freeze-thaw even with low air content.

(3) For the early age compressive strength, comparing with Plain, the strength decreased as addition ratio of fiber and shrinkage reducing agent increased. Whereas for the concrete after curing for 56 days, compressive strength has been generally same with the Plain. All the compressive strength for different types of concrete is identified higher than 80 MPa. For the tensile strength, as different addition ratio of ERCO and SR, tensile strength generally maintained similar or little decreased comparing with Plain. All the types of the tensile strength showed about 10% as same as compressive strength.
(4) For the autogenous properties, with different types and addition ratio of agent, autogenous shrinkage substantially decreased with the increased addition ratio of shrinkage reducing agent. When with the same dosage as ERCO, using SR generally performed better effect about reducing autogenous shrinkage than using ERCO. It would be explained as the principal component of aliphatic acid(C3H5(OCOR)3) in ERCO would be reacted with Ca(OH)2 interior the concrete, 2RCOOCa would be generated and fill the capillary pores interior the concrete. As the solid existed in the position of capillary pores, the effect of shrinkage would be relaxed.

(5) For the fire resistance, when PF fiber was used, the vapour could emission when PF fiber melt in high temperature and considered as effective for explode resistance. When ERCO was used, all the specimen with different W/B did not exploded and belonged to level 1 for magnitude of explosion which considered as good resistance to the explosion.

(6) For the rate of mass reduction, all the specimen with different W/B, the rate of mass reduction is all below 10%, which showed good property for resistance to the explode. For the residual strength after fire, there showed different results about residual strength and residual strength ratio when W/B changed. The specimen showed lower residual strength than Plain which lower than 20%. The correlativity for residual strength ratio when ERCO used was conducted as 0.773 which identified the good effect for using ERCO.

From the shpere of this study, properties as flowability and strength has been sufficiently identified when ERCO was used in high strength concrete. Effect of autogenous shrinkage reducing agent has also been proved as the filling effect in the capillary pores interior the concrete. The filling effect in the capillary pores were speculated as play some role for resistance to the explode. As for the conclusion, when ERCO was used in high strength concrete, it showed good effect on resistance to the explosion as well as autogenous shrinkage reduction effect.
For the residual strength after fire, comparing with using SR, using ERCO showed higher residual strength ratio, but lower than 20% which could not be used after fire, and further study about increase residual strength is needed.