Mixing design and microstructure of ultra high strength concrete with manufactured sand

Abstract Preparation of ultra high strength concrete with manufactured sand is an effective approach to reduce the natural resource depletion and environmental impact of cement concrete industry. In this paper, a new proportion design method was put forward to design ultra high strength concrete with manufactured sand and the microstructure of manufactured sand ultra high strength concrete was observed. Results indicate that the novel method can be applied to design concrete with C120 degree. Ultra high strength concretes prepared with sandstone manufactured sands can have higher strength than those made with river sands. The microstructure of manufactured sand ultra high strength concrete is very dense and the sizes of the hydration products e.g. ettringite, calcium hydroxide and monosulfate Calcium sulfoaluminate hydrates and C-S-H gel become much finer than those in the ordinary concrete. Energy Dispersive Spectrometer result shows that there is no obvious element enrichment at the micro scale of the ultra high strength concrete paste and the hydration products distributes homogeneously. Densely packed and homogenously distributed hydration products with smaller size contribute to the strength of ultra high strength concrete.