ملخص الدراسة:

The aim of this research is to produce Ultra High Performance Concrete (UHPC) in Gaza strip, using materials which are available at the local markets. Different trial mixes are used to obtain a compressive strength exceeding 120 MPa. The research includes the use of mineral admixture (silica fume), basalt aggregate, quartz sand, and special type of fine aggregate (crushed quartz). The mechanical properties of UHPC are studied, i.e., compressive strength, split cylinder strength, and flexural strength. The effect of mixing sequence on the main properties of UHPC, i.e., compressive strength, density, and slump is also investigated in this research work. The effect of adding different amounts of silica fume and crushed quartz on main properties of UHPC, i.e., compressive strength, density, and slump was investigated. The test results revealed that it is possible to produce UHPC in Gaza Strip, with compressive strength in excess of 120 MPa using materials which are available at the local markets, if these are carefully selected and properly mixed in such away to optimize grain size distribution. The equations developed in this research for prediction of splitting strength and flexural strength from compressive strength give close results compared with the relationships recommended in available literature at 28 days age, but have different values at early age of UHPC. The results showed that adding 40 % of the quantity of superplastisizer to the UHPC mixture in the first stage of the mixing to all dry materials (cement, aggregates, and silica fume) avoid agglomeration of silica fume and have pronounced effect on both slump and compressive strength. Based on the results of this research, the optimum percentage of silica fume necessary for producing UHPC is about 15.5 % of cement weight. The results also, showed that the increase in ultra fine dosage increases the cube compressive strength because the finer particles fill up the hollow spaces between the cement and coarser grains.

توثيق المرجعي (APA)