Study On Alkali-activated Phosphorous Sla-Flyash Cementitious Material And Properties Of The Concrete

It is believed that alkali-activated cementing materials deserves more attentions due to its excellent characteristics including no need for high-temperature firing, wide availability of raw materials(industrial solid wastes),good cementing performance, no pollution, etc. A new alkali-activated phosphorous slag-fly ash cement material(APFA cement) has been developed as the initial result of the experiments, with sodium hydroxide and water glass as activator, and make use of this kind of APFA cement to prepare the concrete of different strength, and studied the mechanics function and enduring functions of APFA cement concrete.Through a series of experiments, an applicable proportion of APFA cement which could be used to prepare concrete was founded. The product with optimum proportion of phosphorous slag to fly-ash ratio 85:15 and addition of composite activator, that is, water glass with the modulus of 1.4 and 6% Na₂O, showed high early strength development and high ultimate strength and an appropriate setting behavior.According to the result of the experiments, the APFA cement concrete has higher 28d compressive strength than ordinary 52.5 cement concrete, which can meet the requirements of common concrete completely. The elastic modulus of this concrete is smaller than that of ordinary 52.5 cement concrete. As the result, it is easer to deformation and is more suitable for engineering which needs high anti-crack The frost resistance, chlorine permeability, carbonization performance, and corrosion resistance of the APFA cement concrete were also studied. The results indicated that the frost resistance, anti-chlorine permeation ability, and corrosion resistance of the APFA cement concrete are much better than those ordinary concrete. The reason is that the hydration products and pore structure of APFA cement are different from the common cement. Since the water requirement of the APAF concrete is smaller than that of cement concrete, the structure of APAF concrete is more compacted, this is also an important reason why the APFA cement concrete has good durability.In addition to the mechanical properties and durability, the phase composition, microstructure and pore structure of the APFA cement paste and were analyzed using X-ray diffraction , electronic microscope, and, MIP. The main hydration products of APFA cement are identified as lowly basic C-S-H and hydrated alumino-silicate, with no calcium hydroxide. According to the MIP, the mean pore size in the former is also much smaller than that in the ordinary cement, so that make the mechanical properties and resistance of APFA cement are better than portland cement, which set up the basis for preparing concrete with higher mechanical properties and good durability.