I am surprised that this has not been thought of before, but here they are Lego bricks made from concrete each brick measures just 1 5/8″ L x 3/4″ W x 1/2″ H, which is about the same size as a standard Lego brick. So do not think you are going to be able to build a new house with these little guys!
These are the details on the Lego bricks made from concrete;
These bricks were hand cast to resemble a standard 2 x 4 LEGO building block. They make a great gift for an architect, builder, or anyone who’s a fan of LEGO. Each brick measures approximately: 1 5/8″L x 3/4″W x 1/2″H. Due to the nature of the material each brick is has its own unique colour and texture. Please contact me if you are interested in purchasing more than six blocks. LEGO® is a trademark of the LEGO Group of companies, which does not sponsor, authorize or endorse this site
Priced at $8.50 in USA and £5.41 in the UK for a set of six bricks