Study of the influence of the mortar fine recycled aggregate ratio and the mixing sequence on the behavior of new mortars

Abstract

The objective of this study was to investigate the behavior of mortars by replacing a natural fine aggregate (NFA) with mortar fine recycled aggregate (MFRA), with dimensions of less than 2.4mm. In addition, the influence of the mixing sequence over the performance of these mortars was analyzed. For this purpose, the replacement contents, by weight, of 20% and 40%, and two mixing sequences were adopted: the sequence of the Brazilian Standard, NBR 7215 (ABNT, 1996) and an adaptation for mortars (MDE, in Portuguese, Mistura em Duas Etapas) of the Two-Stage Mixing Approach (TSMA), proposed by Tam, Gao and Tam (2005) for recycled concrete. The mortars were produced with cement CPV-ARI, using a mixing proportion of 1.0:5.0 (cement:aggregate, by weight) and a constant water/cement rate of 0.88. To analyze the behavior of the recycled mortars, they were tested in the fresh state and in the hardened state. The study concluded that the partial replacement of the NFA with the MFRA improved some properties of the recycled mortars: the air entrained content and the water absorption rate by capillarity decreased, and the mechanical performance increased. Regarding the influence of the mixing sequence, the adoption of the MDE promoted a better behavior on the mortar properties evaluated.

Analysis and Reuse of the Fine Waste of a Residual Solid Treatment Plant of a Concrete Company to Prepare a Mortar with Hydraulic Cement

“…Author: Gilberto and Monica [10], Material investigated: Recycled fine aggregate, Type of mortar: Hydraulic mortar cement-sand, Specimen resistance at 28 days: 13.5 MPa according to Brazilian standard NBR7215 and 14.3 MPa according to the MDE method, best result to compression at 28 days: 14.3 MPa, Percentage of mixtures: 0%, (20%-80%) and (40%-60%), Conclusion: The partial replacement of the NFA with the MFRA using the MDE sequence gave the best results. Author: Álvaro et al [13], Material investigated: Recycled non-carbonated and carbonated fine aggregates, Type of mortar: Hydraulic mortar cement-sand, Specimen resistance at 28 days: 17.5 MPa, Best result to compression at 28 days: 22.0 MPa, Percentage of mixtures: 0%, (25%-50%) and (50%-50%), Conclusion: Non-carbonated AFR does not reach the design resistance, contrary to the case with carbonates that increase it.…”

“…About the same RCD, Gilberto and Monica [10] investigate the influence of the relationship of the recycled fine aggregate of mortar, replacing the natural fine aggregates by fine aggregate of RCD and in turn analyze the influence on the mixing sequence on their yields, for which they use two percentages of RCD for the elaboration of the experiments according to Brazilian standards both percentages are 20% and 40%, the ratio of the mixture is 1:5 (cement and aggregate by weight). In this regard they conclude that partial replacement improves some properties of mortars with RCD as air content and the rate of water absorption by capillarity decreases, while mechanical performance increases.…”

Concrete-Based and Mixed Waste Aggregates in Rendering Mortars

“…MRA is strongly influenced by the processing and treatment received. Notwithstanding the lack of studies on the incorporation of MRA, some authors investigated those recycled aggregates in masonry mortar [3,4,6,11,12,[24][25][26]. Only a small amount of research has evaluated the incorporation of MRA in rendering mortars.…”