Search Results (2)

The growing demand for lightweight aggregates (LWAs) in the construction industry is driving the development of sustainable alternatives based on the reuse of solid industrial waste. The aim of this study was to assess the technical feasibility of using red ceramic waste (RCW) as a partial or total substitute for red clay (RC) to produce lightweight expandable aggregates. Six formulations were made with different proportions of RCW and RC and sintered at four temperatures (1100, 1150, 1200 and 1250 °C). They were characterised using physical, thermal, morphological, chemical and mechanical analyses, according to standard protocols. The results showed that almost all the formulations sintered at 1200 and 1250 °C had a positive bloating index (BI > 0), particle density of less than 2.0 g/cm³, low water absorption of less than 2% and mechanical strength of more than 5.4 MPa, revealing strong potential for use in lightweight structural and non-structural concrete. The main conclusion is that RCW, even used in isolation, has physicochemical and mineralogical properties suitable for the production of lightweight aggregates under optimised thermal conditions, contributing to the development of sustainable materials with a competitive technical performance compared to commercial LWAs. Full article

This study aimed to develop marine alkali paste (MAP) produced using seawater (SW), recyclable particle material from paste specimens (RPPs), and alkali agents including NaOH (NH) and Na₂O·3SiO₂ (NS). The physicochemical properties and strength of the MAP were investigated with uniaxial compression tests (UCTs), an Energy-Dispersive Spectrometer (EDS), X-ray diffraction (XRD), and thermal-field emission scanning electron microscopy (SEM). The key information on the MAP preparation and experiments, including mix ratios, ages, curing, and sub-specimen locations, were recorded during the investigation. The results indicated that 8-day-old MAP prepared with NS reached a maximum compressive strength of 8.3 MPa, while 8-day-old NH-prepared specimens achieved up to 5.59 MPa. By 49 days, NS-prepared MAP had strengths between 5.46 MPa and 7.34 MPa, while the strength of NH-prepared MAP ranged from 3.59 MPa to 5.83 MPa. The key hydration products were Friedel’s salt (3CaO·Al₂O₃·CaCl₂·10H₂O, FS), xCaO·SiO₂·nH₂O (C-S-H), CaO·Al₂O₃·2SiO₂·4H₂O (C-A-S-H), and Na₂O·Al₂O₃·zSiO₂·2H₂O (N-A-S-H). C-S-H was generated under the critical curing and working conditions in SW. C-A-S-H development contributed to C-S-H network compaction. N-A-S-H development helped in resistance to SO₄²⁻ erosion, thereby cutting down ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O) development. The active ion exchange between MAP and SW mainly involving SO₄²⁻ and Cl⁻ led to the significant formation of FS at the interface of C-A-S-H and xCaO·Al₂O₃·nH₂O (C-A-H). Therefore, FS generation inhibited SO₄²⁻ and Cl⁻ corrosion in the MAP and rebounded the interface cracks of the hydration products. Consequently, FS contributed to the protection and development of C-S-H in the MAP, which ensured the suitability and applicability of the MAP in marine environments. Full article