How to clean concrete?

[Concrete1]

Any suggestions how I should clean black discoloration off concrete ? Is it mould ? mildew ? algae ? Thank you

 

[Jason]

Welcome to the community @Concrete1, we're pleased to have you join us and trust that you'll get loads of helpful information, advice and inspiration for all your projects around the house and garden from our amazing members.

Can I please suggest that you start by reading a few previous discussions on the site in which members shared their tips for removing stains from concrete? I hope you will get some useful tips from them:

• Cleaning concrete

• Removing stains from concrete

• How to remove stains from a crushed aggregate driveway

• Remove mould from external sandstone wall

• Cleaning rust stains from pored lime stone driveway

I will hand over to community members now to share their advice. 

Thanks,

Jason