I want you to act as an academician. You will be responsible for explain the sentence in detail and help people understand the meaning. My first suggestion request is explain what is the meaning of expressed in terms of total mixture content or recycled binder replacements "in addition, the current Superpave mix design standards and many agency specifications specify using a softer virgin binder performance grade when the amount of recycled materials in the mixture exceeds certain thresholds, expressed interms of total mixture content or recycled binder replacements." Add stress words that are fully capitlized. Make sure these stress words appear more than 13 times.
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