I have a Travertine tile pool deck with very fine grout lines or openings between each tile. No grout or sand just a crack between tiles. I believe they were originally installed edge to edge. Some have shifted with time and there are some that have a little movement when we walk on them. I seem to remember some advice in here that said to mix sand and a small amount of Portland cement and then sweep it into the cracks. Water lightly and..there you go...cracks filled with something stable. Did I actually read that advice or did I dream it?!?! Is that the proper way to fill the lines and provide a little more stability? Thanks in advance for any and all comments!