Design and Testing of Bioreceptive Porous Concrete: A New Substrate for Soilless Plant Growth

Abstract

Porous concrete with a high void content has gained popularity in urban environments as it allows water to spread through its pores. Permeability is a desired characteristic when developing media for plant growth as it enables roots to spread and anchor themselves. This leads to the aim of this study, developing a porous concrete substrate for plant growth with a pH lower than that of standard concrete. The substrate incorporates recovered industrial byproducts from blast furnaces. The materials used in the design consist of a blast furnace slag binder, two proprietary alkali activators, quartz aggregates (2.0–3.2 mm in size), a void content of 30%, and a water to binder ratio of 0.295. Tomato (Solanum lycopersicum), radish (Raphanus raphanistrum), and romaine lettuce (Lactuva sativa) were seeded onto the slag porous concrete for a 28-day hydroponic experiment. The treatments with porous concrete substrates differed in concentrations of the nutrient solution: Hoagland normal (1×), double Hoagland (2×), and quintuple Hoagland (5×). Rockwool with a 1× nutrient solution was selected as the control treatment, a hydroponic standard for plant growth. The dry mass values of the 2× treatment and the control treatment were similar (P > 0.05). The largest dry mass of all treatments investigated was the radish in the 2× treatment at 125.4% of the control radish dry mass.