To obtain a hydraulic composition capable of using in field which requires low alkalinity of pH ≤10.5, through the composition has not high solidification strength and especially useful as a solidifying material for vegetation soil and an improving material of soil.

This low-alkaline hydraulic composition comprises 40-60 wt.% portland cement and 35-55 wt.% calcium superphosphate which are main components and optionally %h10 wt.% anhydrous gypsum. The strength of soil solidified by using the composition containing these three components is 0.7-7.8 kgf/cm2 by uniaxial compression test (aging period: 7 days) and the pH vale is 8.9-10.3.