What would cause clumping?

Just want to clarify that I am NOT asking for medical advice. I am wondering about the chemistry of the litter and what could possibly cause it to behave this way.

Recently my cat has had some issues with bl00d in her urine. Weirdly, when there is blood in her urine it causes the litter to clump together and form a decently hard clump of the litter. This does not happen at all with my other cat’s urine. I am wondering if anyone here is familiar with the chemistry of pretty litter and may know what could cause urine to clump like this.