Ultra-high performance concrete(UHPC)has been increasingly applied due to its ultra-high toughness and durability.However,the mixing of UHPC requires specialized mixing equipment.In the application,the mixing ground is far away from the pouring ground,which requires UHPC to have a high slump retention effect.For the preparation of high slump retention UHPC,two kinds of high performance polycarboxylic acid water reducing agents,named standard type and retarding type,were used to study the effects of their dosage on the setting time,workability(slump retention effect),homogeneity and strength of UHPC.The results show that:With the increase of water reducing agent content,the setting time of UHPC mixed with two kinds of water reducing agents increased,and the slump retention effect also increased,but the viscosity value and early strength of UHPC decreased.Compared with standard water reducing agent,retarding type water reducing agent can significantly prolong the setting time of UHPC,but the initial slump expansion of mixed UHPC is smaller and the slump retention effect is poor.Qingshuitang Bridge high slump retention UHPC is prepared with standard water reducing agent,the content of water reducing agent is 0.8％,the slump expansion degree of mixed UHPC is between 650-750 mm and the viscosity value is between 2 700-3 200 mPa·s within 0-5 h after pouring out of the machine,the pumping performance and slump retention effect are excellent,with good homogeneity,effectively avoiding steel fiber settlement,and the 1-day strength reaches above 35 MPa.The engineering application effect is good.
high slump retention UHPCsetting timehomogeneityearly strength
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