砌筑砂浆应采用机械搅拌,搅拌时间自投料完起算,水泥砂浆和水泥混合砂浆不得少于 ,水泥粉煤灰砂浆和掺加外加剂的砂浆不得少于 。( )
A.60s,120s B.60s,180s C.90s,120s D.120s,180s
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