Hello,
As per your requirement, i would say that the syllabus includes the btech topics of civil engineering as gate is needed for mtech or jobs in psu . The syllabus basically remains of btech civil engineering only.
For more details, check
https://engineering.careers360.com/articles/gate-syllabus-for-civil-engineering
Good luck
You may got through the following pdf for detailed syllabus of GATE for Civil Engineering-
https://static.careers360.mobi/media/uploads/froala_editor/files/GATE-2020-Syllabus-Civil-Engineering.pdf
Also, for more information related to GATE Civil Engineering, you may consider going through the following article-
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