Macrodefect-free cements: The effect of chemical composition on microstructure

The mechanical properties and microstructures of three macrodefect-free (MD F) composites, prepared from Portland and high or medium alumina cements, w ere evaluated. Transmission electron microscopy shows that the interface be tween cement grains and the polymeric matrix is porous in the case of alumi na cements and pore free in the case of Portland. The analyses of the ions present in the polymeric matrix were performed by energy dispersive X-ray s pectrometry, and surface free energy of the materials was estimated through dynamic contact angle measurements by using a Wilhelmy microbalance. The r esults suggest that Fe3+ and Al3+ ions interact differently with the polyme ric matrix. This fact is also supported by dynamic mechanical thermal tests . When Portland cement is used, the microstructure of the MDF composite doe s not show any interphase region.