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From Aug 2006 - Nov 2013 WeDig provided a live forum for diggers & fans of Vindolanda. It has now been mothballed and will be maintained as a live archive.

Here you will find preserved 7 years of conversation, photos, & knowledge about a site many people love. Vindolanda gets under the skin. (Figuratively and literally as a volunteer excavator!) It's a place you remember, filled with people you remember!

Thanks for 7 great years!

Viewing Single Post From: Mike's Geoblog
Mike McGuire
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For proper cement, the clay minerals in the shale need to be heated to high temperature to release the oxides of silicon and aluminium (known as silica and alumina). It is these which react with the calcium oxide (lime) from the limestone to create the hard cement mortar or concrete. I assume Prof. Eric's shale mortar had shale instead of sand as a filler in a basic lime mortar, possibly because although there's plenty of sandstone in the area there's not a lot of loose sand. It's possible that the minerals in the shale get involved in the setting process and create a slightly harder mortar, but you would need to be an expert to know about this.

Glad you're still enjoying the blog, Harry. Sorry we didn't see you here this last week. I had also planned to do a week's excavating then but I didn't want to risk the back, which is only improving slowly (the dog bite is healing well). Andy still has hopes of getting me into the trenches before the end of the season.

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Mike's Geoblog · Excavation & General Archaeology Discussions - Open to All!