Papers by Keyword: Ultra High Performance

Abstract: Using experimental study, major emphasis of the present study is to determine the influence of reinforcement ratio on structural behavior of the prestressed beams made of UHPCC in terms of first crack load, peak load, ductility, and load-deflection characteristics. A UHPCC mixing proportion was presented firstly. 8 rectangular beams of size 100x300x3000mm made of UHPCC were designed, fabricated and tested in this investigation. Influence of reinforcement ratio of load bearing capacity, deflection and crack pattern of beams were performed and analyzed. Based on experimental results, some conclusions were drawn.

Abstract: The analysis of material variables and curing procedure design are the key techniques of UHPCC. Material variables include cement-water ratio, silica fume content, sand’s content and size, filling powder’s content and type. Based on the objective of compressive strength, UHPCC with compressive strength 180MPa was developed based on the influence analysis of material variables on its performances and the substitution of silica fume by lime stone powder. By the analysis of the influences of early curing method, initial time, duration time and high temperature curing, curing procedure design was proposed, i.e. early water curing at first after 24 hours of casting and then high temperature steam curing. Based the simplified constitutive relation of UHPCC, the ultimate flexural of UHPCC hybrid girder was analyzed. This paper can be a basis of UHPCC-NC hybrid structure analysis.

Abstract: Silica fume constitutes an element of extreme importance in improving the strength and fluidity of UHPC. The adopted amount of silica fume generally is generally exceeding 25% of cement in weight but the influence of this amount on the properties of UHPC is still remaining as a domain to be investigated. Accordingly, this paper investigates the effects of the amount of silica fume on the mechanical characteristics of the fluidity, compressive strength, elastic modulus and flexural strength and on the micro structure of UHPC by means of SEM and MIP. Results revealed that adequate amount of silica fume is improving the fluidity and strength. MIP tests demonstrated that such improvement is brought by the increase of hydrates due to the pozzolan reaction and the effective densification inside concrete due to the filler. It seemed also that similar mechanical characteristics can be obtained for a volumetric ratio to cement ranging between 10 and 25%.

Abstract: Direct uniaxial tension test of ultra high performance cementitious composites I shape specimens have been investigated in this paper. A nonlinear analytical model based on continuum damage mechanics is developed to characterize tensile stress-strain constitutive response of UHPCC. Basic governing equations of damage evolution and material constitutive relation are established considering random damage which conforms to a modified Weibull type distribution proposed in this paper. Calculation suggests that Weibull distribution can describe damage evolution of UHPCC and predict the constitutive relation and damage evolution equation.