| Ultra High Toughness Cementitious Composite is a new type fiber reinforced cementitious composite. When subjected to uniaxial tensile loading, it exhibits pseudo strain-hardening phenomenon associated with the multiple cracking phenomenon, which is significant for the crack control and structure durability of cement-based composites. Fly ash is one of the blendings of UHTCC. In order to make full use of local available resources and reduce the cost, it is a necessity to research the influence of fly ash from different habitat on the properties of PVA-UHTCC, which will be a reference for the application of fly ash in PVA-UHTCC. And so, work has been done in this paper as follows:(1) By means of fluidity test, dosage of water reducing agent for PVA-UHTCC with different kinds of fly ashes has been investigated. Results indicate: dosage of water reducing agent for class I high calcium fly ash is the least, and that for class I low calcium fly ash is decreasing with the glass quantity. Class II fly ash can't be applied to PVA-UHTCC in this paper just by increasing dosage of water reducing agent for its great water requirement.(2) Through four-point bending test, influences of fly ash's habitat and quality and water/binder ratio on flexural properties of PVA-UHTCC at 14 curing age have been presented. Consequences show: All the class I fly ashes from different habitats in this paper can make PVA-UHTCC performance multi-cracking and pseudo deformation-hardening behavior, with a little difference in first cracking strength , ultimate flexural tensile strength, multi-crack width and crack space for fly ash's different activity. However, class II fly ash can't be applied to PVA-UHTCC in this paper for its great water requirement. Different water/binder ratios in a certain range can be used in PVA-UHTCC with pseudo deformation-hardening phenomenon associated with multi-cracking phenomenon as well.(3) Through four-point bending test, developments of the flexural properties of PVA-UHTCC with different fly ashes under different curing ages have been tested. Results show: With the growth of curing age, PVA-UHTCC with different kinds of class I fly ashes indicate the same results that the cracking strength increases with the strength of matrix as well as crack width and crack space while ultimate flexural tensile strength increases first and descends a little afterwards for bond slip between fiber and matrix. (4) Through four-point bending test, the effect of curing temperature on flexural properties of PVA-UHTCC has been investigated by means of standard curing at 20°C and water-bath curing at 55℃. Results indicate: PVA-UHTCC under standard curing subjected to bending action performance multiple fine cracks, and that with the comparative strength under water-bath curing present wider average crack width and crack space for the looser porous microstructure because of the faster development of strength caused by high curing temperature. |
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