Formulating Low-Energy Cement Products

• Published in: Journal of materials in civil engineering 2012-09, Vol.24 (9), p.1125-1131
• Main Authors: Rust, David, Rathbone, Robert, Mahboub, Kamyar C, Robl, Tom
• Format: Article
• Language: English
• Subjects: Applied sciences; Ashes; Blends; Buildings. Public works; Byproducts; Cement concrete constituents; Cements; Compressive strength; Exact sciences and technology; Low energy; Materials; Properties and test methods; Properties of anhydrous and hydrated cement, test methods; Strength; Technical Papers; X-ray diffraction
• ISSN: 0899-1561; 1943-5533
• DOI: 10.1061/(ASCE)MT.1943-5533.0000456

AbstractThe study examined several formulations that may serve as a green substitute for traditional portland cement. The primary objective of the project was to produce a durable, low-energy cementitious material from flue gas desulfurization (FGD) gypsum that was converted to hemihydrate. The study also included spent ash from circulating fluidized bed combustion (CFBC), and Class F fly ash. Hemihydrate would give the by-product cement early strength development, and the spent-bed/ultrafine ash blend would provide the by-product cement with long-term strength (gaining slowly at first) and decrease solublity. A spent-bed/ultrafine ash ratio of 40/60 produced the best compressive-strength results of the preliminary clinkerless cement blends produced in the study. The expansion of these clinkerless cements was caused by the formation of ettringite shown by X-ray diffraction (XRD). The system stopped expanding when calcium hydroxide was largely consumed. Substituting 50% of the clinkerless cement blends with hemihydrate increased short-term compressive strength 200% and reduced longer-term expansion up to 90%, enabling the production of low-energy 100% by-product cement.