PHP handle time value over 24:00H

PHP handle time value over 24:00H

I'm addditioning time value of a schedule. When The value go over 24:00
I'm begining to have a problem..
Here is a simple example of what i'm trying to do.
$now = strtotime("TODAY");
$time_1 = strtotime('08:00:00') - $now;
$total = $time_1 * 5;
$total = $total + $now;
echo date('H:i', $total);
The echo value is 16:00:00 But it should be 40:00:00
24:00:00 + 16:00:00 = 40:00:00
So I understand that this is 1 day and 16 hours.
How can I echo 40:00:00