Study of Behaviour of High Strength Concrete Produced from Local Materials and Equivalent Compressive Stress Block

This research presents an experimental study behaviour of high strength concrete, for evaluation of stress - strain curve and derivation of factors of equivalent compressive stress block, we depend it in design of high strength concrete elements. For this purpose, number of cylinders specimens with strength 60 MPa were prepared and tested in compression, then curve was obtained. The results showed the possibility of producing high strength concrete from local materials and with strengths are highest than those were obtained, the resulting diagrams of curve are shown to be essentially linearly elastic up to failure with a steeper declining portion of the stress - strain diagram, which agree with the results of global researches, the failure was almost sudden and rapid with increasing strength which shows that the highstrength concrete less ductile than normal concrete at the failure. Curve of high strength concrete differs from that normal concrete, this affects on the properties of rectangular equivalent stress block which requires modifications on the factors led to optimum represent for it and with evaluation of curve of the tested specimens, the diagram takes a trapezoidal shape ( ), its value at the top is and the depth of the compressive block is and we found and ( is average compression/cylinder compressive strength of concrete, is ratio of the active depth that defined location of compression force center), when concrete strength increases up , the diagram shape will be closer to triangular than trapezoidal and then curve takes the shape of triangle its value at the top is and the depth is and with replacing triangular diagram to rectangle.

Studying the effect of cross section shape on shear resistance of high strength concrete T beams, and developing a relationship to compute it´s shear

Using high strength concrete made a big step in designing and constructing reinforced concrete structures. In this research, shear resistance of high strength concrete beams with average resistance of (65Mpa) and without shear reinforcement was calculated by making Experimental tests, also we studied the effect of cross section shape on shear resistance, and measured the deflection in the middle of the beams then we compared these results with the mathematical results and with results from other researchers, finally we developed a relationship to determine shear capacity in high strength concrete T beams.