In　recent　years,　the　production　of　construction　waste　is　increasing,　and　its　composition　is　complex,　especially　the　high　content　of　red　brick,　which　leads　to　the　obvious　higher　water　absorption　rate　of　recycled　aggregates　compared　to　natural　aggregates.　Therefore,　the　original　concrete　mix　design　method　isn＇t　applicable　any　more.　On　the　other　hand,　there　is　no　safe　and　cheap　backfill　material　for　the　trenches　after　laying　underground　pipelines.　In　order　to　solve　these　problems,　the　present　study　utilizes　Construction　and　Demolition　Waste　to　develop　a　fully-recycled　concrete,　namely　backfilling　concrete,　which　is　specially　used　for　supporting　the　backfilling　of　trenches.　The　water　absorption　of　recycled　aggregate　soaking　in　water　for　different　durations　is　tested.　Based　on　the　growth　law　of　the　water　absorption　of　recycled　aggregate,　the　additional　water　consumption　is　determined　for　the　recycled　concrete　mixing　process.　The　workability,　including　slump　and　bleeding　rate,　and　compressive　strength　of　the　backfilling　concrete　with　16　compositions　with　different　cement-water　ratio　and　sand　rates　are　studied　in　the　paper.　An　empirical　formula　pertaining　to　the　consumption　of　mixing　water　is　proposed,　and　the　parameters　in　the　Bolomey　formula　concerning　the　performance　of　aggregate　are　modified　based　on　the　method　for　designing　the　regular　concrete.　At　last,　the　finite　element　analysis　is　carried　out　with　ABAQUS　for　the　new　type　of　recycled　concrete.　Experimental　and　simulation　results　show　that　slump　of　the　mixtures　using　30-min　water　absorption　of　recycled　aggregates　as　additional　water　is　around　10　cm,　and　the　workability　meets　the　practical　requirements.　The　compressive　strength　of　the　construction-waste-based　concrete　is　between　1　and　3　MPa.　And　backfilling　concrete　can　effectively　protect　the　underground　pipelines　and　road　structure　under　the　vehicle　load　according　to　the　finite　element　analysis.　Consequently,　in　this　paper,　the　original　concrete　mix　design　method　is　improved　and　completed,　which　can　be　applied　to　ultra-low　strength　recycled　concrete.　The　newly　proposed　backfilling　concrete　has　good　workability　and　mechanical　properties　for　backfilling　of　trenches.　Moreover,　cement　consumption　of　it　is　low　to　50　kg/m(3),　which　meets　both　economic　and　environmental　requirements.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.