Experimental investigation on optimization of vegetation performance of porous sea sand concrete mixtures by pH adjustment

The purpose of this paper is to investigate the effect of different methods on reducing the pH value of soil in Porous Sea Sand Concrete Mixtures (PSSCM) through a series of experiments. Thereinto, the X-ray diffraction (XRD) technology was applied to analyzing the mechanism of pH value change, and the relationship between the fundamental performance (effective porosity, sound absorption coefficient and compressive strength) and the optimum mixture proportion of PSSCM successfully. In all experiments, plant varieties which have a high matching degree with PSSCM were screened out, and the vegetation performance of PSSCM was verified by field investigation. Consequently, it is showed that the content of calcium hydroxide in PSSCM was positively correlated with the pH value of soil in PSSCM. The four approaches, adding mineral admixtures, appending acid-modified materials, accelerating carbonization, and immersing Deep penetration sealer (DPS), help reduce the pH value. Among them, the lowest pH value (7.8) was obtained by the addition of 10% silica fume, accelerating carbonization for 28 days, and subsequently immersing in DPS for 28 h. Besides, these methods all reduce PSSCM pore and soil pH value by consuming calcium hydroxide. In addition, the best fundamental performance was obtained on the condition that the water-cement ratio of PSSCM was 0.26 and the effective porosity of PSSCM was 25.95%. Likewise, the matching degree between tall fescue and PSSCM was the best under this pH condition. After 120 days of sowing, their stems were thick and strong, and leaves were green and lush. In the meantime, their rhizomes length exceeds 8 cm. (C) 2020 Elsevier Ltd. All rights reserved.