Alkali-silica reaction (ASR) in concrete is known to be induced by the dissolution reaction where the reactive silica in aggregates is dissolved by the pore solution in the concrete, followed by a precipitation reaction leading to a gel formation. The rate of the dissolution reaction depends on the pH of the pore solution, which is linked to its alkali content. It is assumed that ASR only can occur if the pH is above a critical limit called “alkali threshold”. The knowledge of the pH in a given concrete is of importance for durability. This paper presents a literature review of different methods to determine the pH and the free alkali content in pore solution and discusses their advantages and drawbacks.