Experimental study on vegetation performance improvement of carbonaceous mudstone aggregate vegetation concrete with its micromechanism

Carbonaceous mudstone aggregates are prone to disintegrate to produce alkaline hydrosols under dry and wet cycles, which affects the planting performance of vegetation concrete (VC). To improve the planting performance of carbonaceous mudstone aggregate vegetation concrete (CMAVC), while considering the soaking time and concentration are the main factors influencing the effect of pH-reducing, pH reduction and performance improvement tests, uniaxial compressive tests under different soaking time and concentration were carried out, and verified by the vegetation tests and microscopic tests. The results show that ferrous sulfate and oxalic acid reduced the pH of CMAVC effectively; 0.9 mol/L ferrous sulfate and 1.2 mol/L oxalic acid are the best ratio of pH-reducing materials to ensure that the compressive strength of CMAVC is more than 5 MPa (require by the specification), which the pH values reduced by 20.4% and 29%, respectively, and after soaking 28d, the uniaxial compressive strength reduced by 9.2% from 5.64 to 5.12 Mpa and 5.7% from 5.64 to 5.32 Mpa; Moreover, the reaction of oxalic acid with calcium hydroxide, calcium carbonate, and calcium alumina produces calcium oxalate stone, which fills the internal pores of CMAVC to ensure the excellent mechanical strength and planting effect.