Resistance of geopolymer and Portland cement based systems to silage effluent attack

Abstract

Abstract:Traditional Portland cement (PC) concrete has been used for many years in the agricultural industry for the construction of silos and silage effluent storage facilities. However, the acidic nature of the silage effluent produced by silage has led to severe degradation of PC concrete which in turn has significant environmental and financial implications. This study compares the resistance of PC and geopolymer (GP) mortars and pastes to silage effluent over 12 months. The GP samples displayed increased resistance to silage effluent in terms of mass and strength loss. Analysis of microstructure suggests that the increased stability of the reaction products is the main factor behind increased silage effluent resistance when compared with PC. It was also found that pulverised fuel ash (PFA) and ground granulated blast furnace slag (GGBS) blends with a higher PFA content may offer increased long term silage effluent resistance due to the nature of the main binder gel produced in PFA dominant systems.

Effect of slag content and activator dosage on the resistance of fly ash geopolymer binders to sulfuric acid attack

“…Furthermore, the decalcification of C-S-H was detected which alongside the dissolution of calcium hydroxide results in a very porous corroded layer and a decrease in compressive strength [122]- [124]. On the other hand, the decalcification of the C-A-S-H and/or C-N-A-S-H type gel present in GP2, GP3 and GP4 results in a dense highly siliceous layer which is more resistant to further acid attack [110], [125], [126]. The calcium, which has been removed from various phases in the PC mixes reacts with sulfuric acid to form gypsum which causes expansion and softening of the cement paste [127].…”

Radiological characterisation of alkali-activated construction materials containing red mud, fly ash and ground granulated blast-furnace slag

“…Large quantities of specific secondary raw materials can be utilised in Alkali-Activated Materials (AAMs) as solid binders of performance comparable to Portland cement (Ascensão et al, 2017;Bondar and Coakley, 2014;Puertas et al, 2015;Vinai et al, 2016). For new forms of concrete, the use of AAMs incorporating industrial residues reduces CO2 emissions by up to 80 % (Aiken et al, 2017). Although economically viable, market uptake and widespread application of these new types of recycled materials are hampered by public health concerns related to immobilisation of potentially toxic compounds (Sas and Vandevenne, 2015) and in particular radiation exposure from Naturally Occurring Radionuclides (NORs) (Kovacs et al, 2017).…”

Influência da viscosidade da solução ativadora alcalina na trabalhabilidade de argamassas geopoliméricas

“…Geopolímeros são materiais cimentícios sintetizados por meio da mistura de um precursor, fonte de aluminossilicato, com uma solução alcalina [1]. A geopolimerização pode ser dividida em três etapas: (1) dissolução das fases amorfas do precursor pelo ataque alcalino, quebrando as ligações Si-O-Si, Al-O-Al e Si-O-Si; (2) transporte, orientação e condensação das espécies iônicas em monômeros; (3) policondensação e polimerização dos monômeros em uma estrutura cristalina ou semi-cristalina tridimensional polimérica, formada por ligações Si-O-Al-O [2]. A solução ativadora alcalina pode ser simples ou composta.…”

“…Os geopolímeros apresentam um grande campo de aplicação devido às suas propriedades, como: elevada resistência ao ataque de ácidos; à temperatura elevada; ao ataque de álcalis; e o desenvolvimento de elevada resistência mecânica nas primeiras idades [2,3,4,5].…”