1. The problem statement, all variables and given/known data 2. The attempt at a solution For the question 1, I think that it is related to the void of the concrete. The more the aggregate and the lower void. And it will affect the value of Hammer stress. For the question 2, the results of hammer test which are not obtain from the horizontal orientation are not accurate. horizontal orientation like this photo But i don't know why there are three curves for different orientation. like this http://static7.theconstructor.org/wp-content/uploads/2010/09/clip_image0033.gif [Broken] Question3: I don't know what is the pros and cons.. And I have no idea on the another possible setup, maybe fixed two end, no fixed end? Question4: If the size of the concrete is reduced, the strength of the concrete will also be reduced. And it is more applicable when we want to obtain the result qucikly. Thank you all of you.. I have tried my best and hope I can get some inspirations here.