I'm reading Montgomery's Design and Analysis of Experiments. On page 39, he rejected a two-sided $t$-test against the null hypothesis that modified formulation of some cement mortar doesn't change its bond strength, and then, presumably by noticing that samples from the modified formulation has lower mean, he added
One can conclude that the modified formulation reduces the bond strength (just because we conducted a two-sided test, this does not preclude drawing a one-sided conclusion when the null hypothesis is rejected).
I don't get it. How can you make a one-sided conclusion from a two-sided test?
Or more generally, can you make any conclusion beyond the alternative on rejecting the null? If so, can I conclude that the expectation of (un)modified cement mortar is exactly the corresponding sample mean?