Good pictures! For more history of the area and the cement plant, check out this page from the Santa Cruz Public Library:
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www.santacruzpl.org]
The whole thing is worth reading. For an interesting sidebar, use your browser's search function to look for "Santa Cruz Portland Cement Company Pier - 1934". That describes how the cement company used ships to supplement rail hauls of finished cement. In your last picture, a few of the supports for the cement shipping pier are still visible.