Unsaturated Response of Clayey Soils Stabilised with Alkaline Cements

Abstract

The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils is still mostly unknown and unquantified. This is also motivated by the difficulties associated with the experimental procedure required to fully characterise the unsaturated response of the soil, including its direct influence on traditional strength tests. The present paper presents the soil water retention curves obtained for a Portuguese soil before and after being stabilised with Portland cement (OPC) and an alkali-activated cement (AAC). Saturated undrained triaxial tests were also performed for the same curing conditions (0, 28, and 90 days). Previous attempts to characterise the retention curve of soils stabilised with AAC are unknown, and the results showed that the pore volume structure is already formed after 28 days, prior to the full development of the gel matrix responsible for the strength increase between 28 and 90 days. The curve changed after stabilisation, and with each binder, as the OPC presented a higher air-entry value and a narrower suction range compared to the AAC solution. The significant differences between the curves obtained from each binder suggest the future development of a methodology to assess the quality of the AAC stabilisation.

Geopolymers as Alternative Sustainable Binders for Stabilisation of Clays—A Review

“…Moreover, the results show that the long-term strength gain from geopolymerisation exceeded that of the samples treated with equal ratio of OPC. This suggests that long term strength from geopolymer-based binders may compete favourably with those of more traditional binders such as OPC and lime and agrees with [51]. PFA geopolymers have also been used to stabilise gypseous soils and improved sulphate resistance.…”

Mechanical Strength of Saline Sandy Soils Stabilized with Alkali-Activated Cements

“…Recently, alkali-activated materials have emerged as sustainable alternative binders to Portland cement for soil stabilization [20][21][22][23][24]. Alkali-activated fly-ash-stabilized soil samples had acceptable performance against exposure to NaCl solution (5 wt.%) for 28 days, and the mechanical strength did not change considerably [25].…”

Predicting the mechanical behaviour of a sandy clay stabilised with an alkali-activated binder

“…Commercial reagents such as sodium-based activators (e.g. NaOH and/or Na 2 SiO 3 ) are commonly mixed with amorphous silica (SiO 2 ) and alumina (Al 2 O 3 ) rich industrial residues or wastes, such as pulverised fly ash (PFA) (Araújo et al, 2020;Cristelo et al, 2015;Rios et al, 2016aRios et al, , 2016b ; Vitale et al, 2017), palm oil fuel ash (POFA) (Abdeldjouad et al, 2019;Pourakbar et al, 2015), ground granulated blast furnace slags (GGBS) (Bensaifi et al, 2019;Fasihnikoutalab et al, 2020;Thomas et al, 2018;Wang et al, 2020), glass powder, rice husk ash and silica fume (Canakci et al, 2019;Gao et al, 2020;Geraldo et al, 2017). To enhance the activation results, the source of SiO 2 and Al 2 O 3 should be subjected to thermal treatment before being alkaline activated to reduce the amount of crystallisation water and create an amorphous chemical structure, with a very reactive response (Cristelo et al, 2012).…”