Synergistic effect of waste gypsum plasterboard and fly ash as partial cement replacement on fresh-state, microstructural, mechanical and transport properties of foamed concrete

• Published in: Construction & building materials 2025-02, Vol.463, p.140079, Article 140079
• Main Authors: Maglad, Ahmed M., Mydin, Md Azree Othuman, Kaze, Rodrigue Cyriaque, Abbood, Imad Shakir, Tayeh, Bassam A.
• Format: Article
• Language: English
• Subjects: Chloride test penetration; Fly ash; Foamed concrete; Mechanical; Microstructural and transport properties; Portland cement; Waste gypsum board
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2025.140079

Eco-friendly foamed concretes (FC) were produced in the present study using two types of industrial by-products widely available namely fly ash (25 and 50 % by weight) and gypsum board (5, 10, 15, 20 and 25 % by weight) as partial cement substitution. This study employs these waste materials, aiming to reduce the environmental impact and manufacture cost and improving the FCs properties. Effects of FA and WGB on the FC properties were systematically investigated by diverse tests and characterization techniques. Setting time, slump flow test and fresh density were carried out on fresh concretes, while compressive and flexural strength, splitting tensile strength, modulus elastic, porosity, chloride test penetration were performed on hardened FCs (7, 14, 28, 56 and 180 days). The results revealed that incorporating the waste gypsum board (WGB) up to 25 % prolonged the setting times and increased the slump flow of FCs blended without (FA0, reference) and with 25 and 50 % of fly ash (FA25 and FA50). FA25 and FA50 developed high performance in terms of compressive and flexural strength, elastic modulus, low porosity and densified structure than FA0. The high mechanical properties of FA25 (8.30 MPa) and FA50 (6.20 MPa) achieved on specimens at 180 days tend to decline over 10 % of WGB suggesting the presence of voids and large pores which weakened the strength development (4.50 and 3.12 MPa, respectively). The evaluation of the FC mixes using various methodologies has demonstrated that the optimal mix is achieved when WGB and FA are applied simultaneously. FA25 and FA50 well performed in well performed in rapid chloride permeability than reference FA0. The WGB industry would become more viable and have positive environmental effects if WGB and FA were used appropriately in place of cement. FCs containing FA and WGB with controlled density and proper strength can be used in prefabricated buildings and energy-saving insulation components. For large application the obtained results may be helpful in assessing the combined effect FA-WGB additives on the fresh and hardened properties and durability of FCs made with these waste materials. •Combined effects of waste gypsum plasterboard (WGP) and fly ash (FA) on properties of foamed concrete (FC) was evaluated.•Mechanical, transport and microstructural characteristics were investigated.•With 25 % and 50 % FA mixed with WGP, the FC mechanical lead to optimal value compared to 0 % FA.•Mechanical properties tend to decline