2.1　Raw Materials

The ground granulated blast furnace slag(GGBFS)used in the research was produced by Huaxin Cement Co.in Hunan,China.The fly ash(FA)was produced by Lianyuan Power Plant in Hunan,China.Their chemical compositions obtained from the X-ray fluorescence(XRF)analysis are presented in Table 1.Figure 1 shows the particle size distributions of the GGBFS and FA.The former was mainly in the range from 2μm to 50μm while the latter had a wider range from 1μm to 300μm.PC produced by the Anhui Conch Cement Company,China with a specific surface area of 336 m2/kg and loss on ignition of 1.62%was used in this research.Its chemical compositions are also indicated in Table 1.The morphology of GGBFS and FA particles observed by the scanning electron microscope(SEM)is shown in Figure 2,which illustrates that GGBFS particles are predominately of anomalous shape with clear edges and angles while most FA particles are solid spheres.The alkali activator liquid used was a combination of sodium silicate solution and sodium hydroxide.The sodium silicate solution was a commercially available product with a water content of 59%(by mass)and a modulus(the mole ratio of SiO2 to Na2 O)of 3.7.The modulus of the alkali activator was further adjusted to the designed values by adding sodium hydroxide(NaOH)flakes with 99%purity,which was purchased from the Tianjin Bohai Chemical Industry,China.Gravel from local river were used as the coarse aggregate whose bulk specific density was 2 530 kg/m3 with a maximum size of 10 mm.The water absorption of the coarse aggregate was 1.83%.The fine aggregate used was natural,uncrushed river sand.Its specific density,absorption,and fineness modulus were 2 340 kg/m3,2.75%and 2.47,respectively.

Table 1　Chemical composition of GGBFS,FA and PC(%by mass)

Figure 1　Particle size distributions of GGBFS and FA