Production of Alkaline-Activated Mortars Using Red Ceramic Waste as a Precursor

• DOI: https://doi.org/10.22533/at.ed.1317662604062

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• Abstract:

  The growing global demand for civil construction, driven by population growth and increased urbanization, has contributed to a significant increase in cement production. However, this industrial expansion has generated significant environmental impacts. Data from the Brazilian Portland Cement Association indicate that Portland cement, the main component of concrete, stands out as one of the largest emitters of carbon dioxide (CO₂) in the industry, directly contributing to the worsening of the greenhouse effect and climate change.
  Recent information indicates that cement sales in April 2025 totaled 5.2 million tons. Despite a 3.0% decline compared to the same period in 2024, the cumulative total for the first four months of the year showed a 4.2% increase, highlighting continued demand in the civil construction sector (SNIC, 2025). This scenario reinforces the need to develop more sustainable alternatives for the production of cementitious materials. In this context, alkali-activated materials (AAM) stand out as a solution
  Alkali-activated mortars (AAM) are obtained through a chemical reaction between a silico-aluminous precursor material and an alkali-activating solution, resulting in a material with cementitious properties. For the production of mortars in this study, red ceramic waste (RCV) and metakaolinite were used as precursors, while sodium hydroxide (NaOH) was employed as the alkaline activator.
  Three experimental mixtures, designated R00, R05, and R10, were prepared, keeping the water content constant while varying the percentage of hydrated lime (Ca(OH)₂) added. After a 28-day curing period under ambient conditions, tests were conducted to evaluate the material’s mechanical properties.
  The flexural tensile strength and compressive strength tests were conducted in accordance with the guidelines established by Brazilian standards applicable to mortars for laying and coating walls and ceilings. The results indicated that the R10 mix design exhibited the best mechanical performance, achieving a compressive strength of approximately 4.0 MPa, and was classified as a P4-class mortar according to NBR 13279. Additionally, it exhibited a flexural tensile strength of 2.3 MPa (Class R4).
  The bulk density of the hardened R10 mix was classified as M6, with a value of 1981.032 kg/cm³, while the capillary coefficient was 6 g/dm²·min¹ᐟ², falling under Class C4. These results indicate that the developed material has potential for application as a laying and coating mortar, meeting the requirements established by Brazilian standards.