| Experimental results on the content of porous concrete（POC）and its influence on the strengths and modulus of elasticity are reported．The void content accounts fou the total volume through which plant roots can reach the natural soil below the greening concrete and water can flow inside the procedure proposed by eco-concrete research committee of the Japan Concrete Institute．Sets of curves illustrating the effects of cement and water contents on void content and the relationships between void content and strength properties of POC were constructed and analyzed．Main results follow：[*]1）Up to 15％ voids like conventional concrete，the compressive strength is reduced approximately by 5％ for each additional 1％ voids．After this limit the reduction in strength becomes progressively less for every added 1％ void．2）The increase of compressive strength is not proportional to that ofcement content．For a given aggregate-cement ratio there is a very narrow optimum range of water-cement ratio that leads to maximum strength．3）The secant modulus of elasticity decreaes by about 1 GP afor each 2％ increase of void content and might be predicted using AC 1318－89 Mdeveloped equation． |
