Esperanza Menéndez Méndez (deceased), PhD from Polytechnic University of Madrid, was Researcher at IETcc-CSIC (Instituto Eduardo Torroja de Ciencias de Construcción - Spanish National Research Council), where she served as Head of the Physic-Chemistry Testing Unit. She was a leading expert in several techniques of characterization of construction materials, pathology and durability of concrete structures, buildings and cultural heritage.António Santos Silva, PhD in Civil Engineering from Minho University in Portugal, is Senior Researcher at the Materials Department of LNEC (Laboratório Nacional de Engenharia Civil - National Laboratory for Civil Enginnering. His research interests focus on building materials, including its characterization and performance, mitigation of internal expansive reactions in cement-based materials, and compatible materials for conservation of historical heritage.

• Introduction.- Sources of alkalis.- Analytical methods to determine the alkalis.- International standards and recommendations.- References.

Esperanza Menéndez Méndez (deceased), PhD from Polytechnic University of Madrid, was Researcher at IETcc-CSIC (Instituto Eduardo Torroja de Ciencias de Construcción - Spanish National Research Council), where she served as Head of the Physic-Chemistry Testing Unit. She was a leading expert in several techniques of characterization of construction materials, pathology and durability of concrete structures, buildings and cultural heritage.António Santos Silva, PhD in Civil Engineering from Minho University in Portugal, is Senior Researcher at the Materials Department of LNEC (Laboratório Nacional de Engenharia Civil - National Laboratory for Civil Enginnering. His research interests focus on building materials, including its characterization and performance, mitigation of internal expansive reactions in cement-based materials, and compatible materials for conservation of historical heritage.

• Introduction.- Sources of alkalis.- Analytical methods to determine the alkalis.- International standards and recommendations.- References.

Esperanza Menéndez Méndez (deceased), PhD from Polytechnic University of Madrid, was Researcher at IETcc-CSIC (Instituto Eduardo Torroja de Ciencias de Construcción - Spanish National Research Council), where she served as Head of the Physic-Chemistry Testing Unit. She was a leading expert in several techniques of characterization of construction materials, pathology and durability of concrete structures, buildings and cultural heritage.António Santos Silva, PhD in Civil Engineering from Minho University in Portugal, is Senior Researcher at the Materials Department of LNEC (Laboratório Nacional de Engenharia Civil - National Laboratory for Civil Enginnering. His research interests focus on building materials, including its characterization and performance, mitigation of internal expansive reactions in cement-based materials, and compatible materials for conservation of historical heritage.

• Introduction.- Sources of alkalis.- Analytical methods to determine the alkalis.- International standards and recommendations.- References.