I have been trying to solve this same issue today so thought I would post my code in case other were having a similar issue
<?php
$slug = get_page_by_path( 'blog' );
if (is_single()) { ?>
<h1><?php echo the_excerpt(); ?></h1>
<?php } elseif (is_home()) { ?>
<h1><?php the_field('page_heading', $slug->ID); ?></h1>
<?php } else { ?>
<h1><?php the_field('page_heading'); ?></h1>
<?php } ?>