What is the best tile adhesive to use outdoors on concrete steps?

PowerGrab has done well for us. It's made by Loctite and available at most hardware and big box stores. It does have a slow dry time so keep that in mind.

Visit your local stand alone tile shop. They carry all the things you need. Basically what you use inside but the exterior rated stuff. Be sure to tell them you are doing glass tile because you'll need the white mastic, not the other because the color will show thru.

I love Loctite heavy duty construction adhesive. It comes in a caulking tube.

use sanded grout for outdoor areas

You can also buy sanded caulk. Grout is not what you want to use between tile and another material (like a wood riser leading into your front door) that's not some type of stone because they expand and contract differently leading to the grout cracking. The sanded caulk will have the appearance of grout and be flexible. Also, you do not use mastic with glass tile. You will need to use the appropriate thin set mortar.

mortar mix is the best

Thinset mortar to adhere the mosaic tile. Sanded grout for the joints. Grout sealer for the joints and nothing on the tile. Construction adhesive will fail on tile. if you were laying pavers or patio blocks then construction adhesive would work.

Thinset mortar is your best bet.

This tutorial might be helpful: https://www.diynetwork.com/how-to/skills-and-know-how/masonry-and-tiling/how-to-give-a-tile-facelift-to-an-ordinary-concrete-porch

I would use mortar

Here's a post that might help you - https://www.tilemountain.co.uk/blog/best-adhesive-and-grout-for-outdoor-tiles/

Hi Deborah, hope this helps you out, thinset bonding mortar should be used for outdoor mosaics and mosaics where water is an issue, like rain, hail, or snowfall.

You’d use regular tile mortar and grout. When purchasing it, ask what grout sealer might be best for outdoor applications.

That would make the steps slippery when it rains just keep that in mind

always use matching grout caulk on the edges by wall and door. It’s siliconized grout water seal and flexible. Difficult product to apply but tape both sides with painters tape leaving 1/8” gap for caulk line. Smooth and remove tape immediately. Finished result is perfection