Assessing the production of jet mix columns using alkali activated waste based on mechanical and financial performance and CO2 (eq) emissions. (1st September 2015)

• Record Type: Journal Article
• Authors: Cristelo, Nuno; Miranda, Tiago; Oliveira, Daniel V.; Rosa, Ivo; Soares, Edgar; Coelho, Paulo; Fernandes, Lisete
• Is Part Of: Journal of cleaner production. Volume 102(2015:Sep. 01)
• Page Start: 447
• Page End: 460
• Publication Date: 2015-09-01
• Subjects: CO2 production -- Soil stabilisation -- Alkaline activation -- Financial analysis; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2015.04.102
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: Recent research has proved the potential of alkaline activated fly-ash for soil stabilisation. However, such studies have not focused on the link between financial, mechanical and environmental aspects of this solution, but only on their absolute mechanical properties. The present paper characterises the mechanical behaviour of a large spectrum of activator-ash-soil combinations used to build jet mixing columns, analysing also the cost and CO2 (eq) emissions. The concern with these two vectors forced a decrease in the quantity of stabilising agent added to the soil, relatively to previous research, and the effects of such low quantities have not yet been published. However, the results clearly showed a significant improve in strength, still well above the average values expected when improving the stress-strain behaviour of a weak soil. Uniaxial compressive strength tests were used to assess the effects of the fly-ash percentage, the alkali–ash ratio and the water content. The carbon calculator recently developed by the European Federation of Foundation Contractors and the Deep Foundations Institute was used to quantify the CO2 (eq) emissions associated with this technique. The financial cost was estimated based on the experience of a major Portuguese contractor. For comparison purposes, soil-cement mixtures were also analysed, using similar conditions and tools used for the soil-ash analysis. Results showed that the cement and ash solutions are very similar in terms of overall performance, with some advantage of the former regarding financial cost, and a significant advantage of the latter regarding the CO2 (eq) emissions. This new grout, although it is in an embryonic stage, it has the potential for broader developments in the field. Highlights: Alkali activated fly ash grout is validated for jet mix columns. Comparison with a cement grout reveals similar mechanical performance (UCS tests). CO2 (eq) emissions are significantly lower than those obtained with cement. Financial cost is still higher than traditional solutions (1.1×). Significant margin for development, which can increase effectiveness.