Experimental Investigation On Recycled Concrete Base Course Involved In High Dosage Recycled Aggregate

Reasonable utilization of waste concrete is one of the important ways to realizesustainable development in the field of concrete. In the process of upgrading old roads, howto seek cost-effective technology to inhibit or delay appearing the reflection crack has beenone of the difficult problems in the road construction field. In this paper, applying wasteconcrete materials as the recycled concrete to the road base has been theoretically analysedand researched through systematic tests content mainly, including the following severalaspects:(1) This paper has discussed the basic physical properties, mechanical properties anddurability of the mortar specimens which are totally made of recycled fine aggregate. Testresults show that when graduation is the same standard mortar, water-cement ratio is1:2,cement-sand ratio is1:3, recycled fine aggregate mortar mixture is more loosely, basicallywith no liquidity, the strength is much lower than the standard mortar, and flexural strengthand compressive strength of28d are1.57MPa and4.51MPa, respectively; When thewater-cement ratio is1:0.8, the workability of recycled fine aggregate mortar is the same withstandard mortar, the strength of the recycled mortar increased greatly, the flexural strengthand compressive strength of28d are up to2.74MPa and9.73MPa; Air-entraining agent canimprove the strength of recycled fine aggregate effectively.With the increase of air-entrainingagent dosage, the strength of recycled fine aggregate mortar presents a trend of decrease afterthe increase, when the water-cement ratio is1:2, recycled fine aggregate mortars’ flexural andcompressive strength of28d are1.57MPa and9.74MPa, and the best dosage is0.25%.(2) On base of the best gradation to make of recycled concrete aggregate, the mixproportion of recycled concrete materials is designed. Respectively choosing water-cementratio (0.45,0.50,0.55,0.50) and unit dosage of cement (160kg/m3,180kg/m3,200kg/m3,220kg/m3) as the design parameters to design the mixture ratio of recycled concrete materialsby the contrast and orthogonal experiment design methods. Experimental results show thatwhen the water-cement ratio is0.55and unit cement dosage is220kg/m3, the recycledconcrete7d and28d compressive strength are7.89MPa and11.58MPa, basically meeting thestrength requirement of road base.(3) Based on the best mixture ratio, this paper has researched optimization of therecycled concrete materials and optimization of the process of preparation measures. Testresults show that adding a certain dosage of air-entraining agent can greatly improve the workability of recycled concrete and the recycled concrete air-entraining agent’s best dosageis0.3%; Adding10%of waste polystyrene (EPS) can improve its thermal performance;Blending recycled concrete with magnetized water, to a certain extent, can improve the earlystrength, the strength growth rates of the3d,7d and28d increase by18%,13%and4%,respectively.