Influência de cristalizantes em argamassas estabilizadas feitas em usinas

Abstract

Stabilized mortar emerged in the market during the 1990s as an industrialized product, produced in industrial plants and delivered ready for use on construction sites, representing the sector’s response to the need for increased productivity. Although its production and use began in Brazil around that time, the product initially lacked regulatory standards to ensure necessary quality requirements. Due to the growing demand for standardization and quality assurance, the first official standard was published in 2005 and later revised in 2023. Within this context, the present study investigates the behavior of stabilized mortar when produced in concrete plants using crystallizing additives. Composed of sand, cement, and additives, stabilized mortar can be used within 36 or 72 hours, making it a promising alternative for construction since it arrives ready to apply. However, this innovation shares production infrastructure with ready-mix concrete and faces technical challenges—particularly regarding how additives traditionally used in concrete behave when applied to stabilized mortar. One of the current challenges is understanding the influence of crystallizing additives on mortar performance. This research evaluates two crystallizing additives, Type 1 and Type 2, to assess their effects on the properties of stabilized mortars. The dosages applied were 0.35%, 0.70%, and 1.00% by cement mass, in accordance with the manufacturers' recommendations. A total of seven samples were tested—one without the crystallizing additive and six with varying doses of the two additives. All samples were subjected to tests in the fresh state, including flow table consistency, water retention, and air content, as well as hardened-state tests such as bond strength, modulus of elasticity, compressive strength, and flexural tensile strength. The crystallizing additives improved the workability of the stabilized mortar, showing similar behavior to conventional stabilizing additives. Type 1 reduced workability over time but improved its suitability for use as non-structural masonry mortar due to reduced air incorporation. In contrast, Type 2 maintained better workability over time, but the increased air content may negatively impact its application. While all mixtures complied with fresh-state requirements, not all met the criteria in the hardened state, with bond strength to the standard substrate being the primary reason for disqualification.