No abstract

No abstract

This paper examines the suitability of partially replacing natural aggregate, sand, (NA) with recycled concrete aggregate (RCA) or lightweight aggregate (LWA) in mortars, under the hypothesis that pre-wetting aggregates would produce improvement in mortar properties. Fresh mortar properties such as density, entrained air content, consistency and heat of hydration, as well as hardened mortar properties such as dry density, compressive and flexural strength, and dimensional instability at 0% and 100% saturation were determined. The results show that mortars made with natural aggregate (75%) and recycled concrete aggregate (25%) have similar properties to mortars made with only natural aggregate (100%) and that pre-wetting the aggregates does not influence the properties of mortars significantly. Therefore, partial replacement with recycled concrete aggregate is a viable alternative for producing mortar.

This work deals with the effect in fresh and hardened properties of nano-TiO 2 as addition in cement-based mortars. Three commercial nano-TiO 2 powders were characterized by laser granulometry, XRD, FRX, zeta potential, BET and SEM. Two cementitious mortars were produced with nano-TiO 2 , an industrialized and a non-industrialized type; then, these mortars were characterized by flowability, surface roughness, flexural strength and surface fracture. The results showed that the nano-TiO 2 addition reduced the flowability in terms of spread on table of the mortars. For surface roughness, in the industrialized mortars, the nanoparticles resulted in a smoother surface, while in the non-industrialized mortars, the nanoparticles formed a rougher surface. For flexural strength, in the non-industrialized mortars, the higher the nanoparticles amount, the higher the strength, while in the industrialized mortars no tendency was verified. In addition, from SEM analysis, it was noted that the fracture of the samples presented a tortuous aspect and growth through the region between cement paste and aggregates.