Greener lightweight foam concrete using seaweed industrial by-product to replace natural sand with inorganic salt as a stabilizer

In recent years, the seaweed industry has expanded, resulting in higher volumes of seaweed industrial by-products (SWB). People commonly dispose SWB on land, which raises environmental concerns due to its hazardous chemical content. The use of waste materials as alternatives to natural sand has gained attention due to its potential to reduce environmental impact. Therefore, this study aimed to develop a greener lightweight foam concrete (LFC) by incorporating 0–30 % SWB as a replacement for natural sand in fine aggregates and evaluate its performance. Furthermore, the study investigated the inclusion of inorganic salt concentrations ranging from 0 to 15 % into the concrete mixture to improve performance. The production, sampling, and testing procedures followed the SNI 8640:2018 standards. Properties like density, water absorption, drying shrinkage , and compressive strength were analyzed for SWB percentage (0–30 %), salt concentration (0–15 %), foaming pressure (0.20, 0.39, and 0.59 MPa), and curing duration (7, 14, and 28 days). Viable specimens were further examined for microstructure, energy intensity, CO 2 emission, and production cost. Specimen FS5 met standards with a density of 707.1 kg/m 3 , compressive strength of 2.12 MPa, water absorption of 25.45 % (v/v), and drying shrinkage of 0.13 %. The energy intensity, CO 2 emission, and total cost of greener LFC were calculated to be 159.88 MJ/m 3 , 188.98 kg of CO 2 /m 3 , and IDR 682,130/m 3 , respectively. Ultimately, this work greatly contributes to the field of green manufacturing and environmental sustainability by successfully decreasing energy intensity, CO 2 emissions, and environmental harm in LFC production processes. • Seaweed industrial by-products replace natural sand in lightweight concrete production. • The effect of the inclusion of inorganic salt in the production is also explored. • Seaweed by-product replaces 20 % of natural sand without affecting concrete properties. • Technical, economic, and environmental results are investigated. • The lightweight concrete production in this study qualifies as a green approach.