By embedding 4% fibre-optic threads into fine concrete, the material is made translucent without any appreciable loss of compressive strength. Light trans – mitting concrete can be manufactured as blocks or panels provided that the fibres run transversely from face to face. If one face is illuminated, any shadow cast onto the bright side is clearly visible on the other face, while the colour of the transmitted light is unchanged. Blocks up to 1200 X 400 mm with thicknesses from 25 to 500 mm are standard and can be manufactured in a variety of colours including white, grey or black. The material has many potential applications including walls, floor surfaces and illuminated pavements.