*2.4. Other Tests*

#### 2.4.1. Mass Change

When a specified erosion time was reached, concrete samples were taken from the solution and then dried in a constant temperature room at 22 ◦C until the mass was constant. At the same time, the sample surface was gently wiped with a towel to remove crumbs. The sample mass was then weighed and recorded using an electronic scale with an accuracy of 0.01 g. There were 3 parallel concrete samples in each group when weighing, and the results were averaged. Next, to calculate the rate of mass change Equation (1) was used [38]:

$$
\varphi\_i = (m\_n - m\_0) / m\_0 \tag{1}
$$

where ϕ*i*, *mn*, *m*<sup>0</sup> are the rate of mass change of the concrete specimen, the mass of the specimen after erosion time *n*, and the initial mass (g), respectively.
