Abstract
Abstract Ready-mixed mortars have been increasingly used due to their potential for waste reductions and productivity increases. However, research regarding their use in structural masonry applications are practically non-existent. Thus, this work investigated the technical feasibility of using ready-mixed mortars with nominal compressive strengths of 6, 9 and 14 MPa and storage times of 0 and 36 hours in concrete block structural masonry. The fresh state properties of the mortars were evaluated at 0 and 36 hours through the slump test, consistency and plasticity by the Gtec test, and entrained air content. The compressive and flexural strengths of the mortars were determined at 28 days. In addition, three-row prisms were tested for compressive strength and modulus of elasticity, and four-row prisms for flexural strength in the bending test, all at 28 days. The results showed that the 6 and 9 MPa ready-mixed mortars showed satisfactory maintenance of the fresh properties from 0 to 36 hours and adequate hardened properties for both casting ages, in contrast to the 14 MPa mortar. Regarding the prism tests, the increase in storage time did not significantly affect the properties evaluated for a reliability of 95%.
Highlights
Structural masonry is one of the oldest known building systems but has been changing over the years according to scientific and industrial evolution (MOHAMAD, 1998)
The ready-mixed mortars appeared in the 1970s, which are ready-to-use mortars that can be used for up to three days, while maintaining their characteristics (PANARESE; KOSMATKA; RANDALL, 1991)
These reductions were of 5.0% and 7.0% respectively for the 9 and 14 MPa blocks compared to the 6 MPa blocks. This confirms that increasing the block strength increases its compactness, reducing the water absorption, as reported in the literature (PARSEKIAN et al, 2019). This behaviour was reported by other authors for compressive strengths different from those found in the current work (MARTINS et al, 2018; FONSECA et al, 2019)
Summary
Structural masonry is one of the oldest known building systems but has been changing over the years according to scientific and industrial evolution (MOHAMAD, 1998) In this type of structure, the walls are loadbearing elements comprising masonry units (bricks or blocks) joined by mortar joints and are capable of resisting loads beyond their own weight (PRUDÊNCIO JUNIOR; OLIVEIRA; BEDIN, 2002). The ready-mixed mortars appeared in the 1970s, which are ready-to-use mortars that can be used for up to three days, while maintaining their characteristics (PANARESE; KOSMATKA; RANDALL, 1991). This is feasible due to hydration controller admixtures. The first mechanism is associated with the commonly called "retarder" admixtures and have a faster effect, while the second mechanism is associated with "hydration inhibitors" admixtures, which have a longer effect (HEWLEET; JUSTNES; EDMEADES, 2019), and are conventionally used in ready- mixed mortars
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