Sustainable Development of Civil Engineering Materials Due to Replacement by High Volume of Pozzolanic Materials

Concrete is the most widely used civil engineering materials, and cement is the important component of concrete. There have been enormous demands for cement since the late 1990s in China because of rapid economy development. In cement production process, large numbers of carbon dioxide gas will be emitted and great energy sources will be consumed, resulting in the speedup of greenhouse effect and energy sources crisis. In Chinese sustainable developmental strategy, it is very important to construct eco-friendly and resource conservation society, which is incompatible to environmentally contaminative and resource wasting cement product industry. Pozzolanic materials which are wastes coming from industry product process, such as silica fume (SF), rice husk ash (RHA), fly ash (FA) and granulated ground blast furnace slag (GGBS). After added into concrete, these supplementary materials can afford concrete excellent mechanical properties and durability and reduce the use of cement in concrete, but the pozzolanic materials replacement in cement are often under 30%. In this paper, addition of high volume of fly ash into cement was studied. Mechanical property such as compressive strength and durability such as capability of chloride ion ingress resistance and capability of carbonation resistance of concrete were studied. Results show, that the compressive strength of concrete with 50%similar to 60% fly ash replacement is still above 35 MPa in 0.30 water to binder rate (w/b), which is enough to use in normal concrete structure. With ages increasing, the developing rate of compressive strength of FA concrete is faster than OPC (Ordinary Portland Cement). With the increase of FA replacement, concrete carbonation depth increases at 28 day ages, but with the second hydration reaction going, carbonation coefficients of FA concrete decrease obviously. Replacement of cement with high volume of pozzolanic materials is an effectual way to decrease cement product, making full use of industrial byproducts and reducing the release of deleterious substance, which can sustain sustainable developmental strategy and construct eco-friendly and resource conservation society.