Effect of polycarboxylate superplasticizer on dispersion of carbon fiber in cement-based material

Improving the dispersion of carbon fiber with simple technical methods was helpful to enhance its application effect. In this paper, the dispersion of carbon fiber in solutions of an esters polycarboxylate superplasticizer (PC) and methyl cellulose (MC) was investigated by measuring turbidity; the influence of the dispersing agents on the electrical resistivity and pore structure of carbon fiber reinforced mortar (CFRM) was tested and uniformity of the distribution of carbon fiber was observed using a scanning electron microscope. The results show that the carbon fibers with different length-diameter ratio were dispersed uniformly in the PC solution and the electricity of resulting CFRM increased significantly; but only carbon fibers with small length-diameter ratio did in the MC solution and just the electricity of CFRM with high water-cement ratio increased to some extent. By contrast, the electricity of CFRM made from water reducer FDN, which improved the fluidity, had no significant increase. It is suggested that the water reducer PC had a amount of polar groups adsorbed by the surface of the carbon fiber and increased the repulsion between carbon fibers, therefore improved the dispersion of the carbon fiber in CFRM along with improved the mechanical properties of CFRM. The observation of SEM images and analysis confirmed the positive effect of PC on the dispersion of carbon fiber in CFRM.