You have not supplied sufficient information.

I would consult one of the sample size calculators on the internet, where you will discover that population size has rather little impact on your sample size.

The typical method for justifying sample size calculation is to plan it out, utilizing power analysis performed through specialized software (e.g., G*Power). Statistical power is the likelihood of detecting a statistical result when correlations between variables or differences between groups do exist. Here are some helpful reads.

Brydges, C. R. (2019). Effect size guidelines, sample size calculations, and statistical power in gerontology. Innovation in Aging, 3(4), igz036. https://doi.org/10.1093/geroni/igz036

Kang, H. (2021). Sample size determination and power analysis using the G*Power software. Journal of Educational Evaluation for Health Professions, 18. https://doi.org/10.3352/jeehp.2021.18.17

Good luck,

Based on the information provided, no. However, it may be the only sample size you can get (study site was bombed, taken over my armed people, tilled, grazed, burned, salted, flooded, .....) That is even more funny as the samples were of different concrete mixes. What makes for a reasonable sample?

1) Nature of question being asked.

2) Value of answer gained: not so much the value to you personally, but the value to the funding agency or human society at large.

3) Difficulty or risk in gathering data

4) Variability in the data

5) There are other factors, but often they apply to a specific topic. Source of missing data for example.

A great deal of research is expected to be published. Is this sample size similar to that used in other studies?

How risk adverse are you and how much time are you willing to give to manage that risk? My sample size is at the low end of published research. I arrive at novel conclusions (or no conclusions). This is unpublishable because reviewers will not accept the small sample size. Had I used a sample size at the high end (or more than) previously published work then it becomes publishable anyway (though possibly harder than if everything had worked as expected).