As of Alpha 6 you can create the following sass file:
@each $breakpoint in map-keys($grid-breakpoints) {
$infix: breakpoint-infix($breakpoint, $grid-breakpoints);
col, td, th {
@for $i from 1 through $grid-columns {
&.col#{$infix}-#{$i} {
flex: none;
position: initial;
}
}
@include media-breakpoint-up($breakpoint, $grid-breakpoints) {
@for $i from 1 through $grid-columns {
&.col#{$infix}-#{$i} {
width: 100% / $grid-columns * $i;
}
}
}
}
}