No abstract

Increasing the dry unit weight (γd) through vibration/compaction and the addition of Portland cement are among promising ground improvement procedures to enhance the endurance performance of granular materials. The present investigation intends to compute the impact of cement content (C) and γd on the durability of Osório sand–Portland cement blends. An experimental programme of wetting–drying cycle tests considering distinct γd and C was carried out to assess that influence. A steadiness of the characteristic loss of mass (CLM) during 12 wetting–drying cycles for distinct specimens (of each particular γd and C) is observed and suggests a possibility of carrying out just a few cycles, making possible to extrapolate the results up to the required 12 cycles, reducing the time needed to assess the durability of such blends. It is also shown that the CLM of each specimen is reduced on increasing the γd and C. The CLM and accumulated loss of mass of compacted sand–cement mixes during wetting–drying cycles were originally perceived in the present research to be directly associated with the porosity/cement index. This broadens the applicability of such index, demonstrating that it controls not only the strength but also endurance performance of sand–cement blends.

Waste glass is a solid residue usually available near urban centres, where it is discarded after being used as a container for one of several products. Carbide lime (CL) is a by-product of the manufacture of acetylene gas. The present research evaluates the potential of combining these two wastes as a possible hydraulic cement to enhance the behaviour of sands. Pozzolanic reactions occur between silica in its amorphous phases (found in GG) and Ca++ (present in CL) in an alkaline environment. The effect of the amount of GG, the CL content and the porosity of the blend on the strength, stiffness and durability of compacted sand–GG–CL mixes is quantified for three distinct sands. An original parameter, termed the porosity/binder index (η/Biv), can be used to normalise the behaviour of the unconfined compressive strength (qu), the shear modulus at small strains (G0) and the accumulated loss of mass (ALM) of the compacted mixes, considering GG + CL as the binder. Results have shown unique normalised tendencies for qu, G0 and ALM with η/Biv for the three studied compacted sand–GG–CL blends, even though each sand has a distinct grain size distribution.

The use of industrial residues instead of virgin materials is a good alternative for a more sustainable approach to disposing of and managing waste. Soil improvement with coal fly ash (CFA) is particularly attractive for geotechnical earthworks. This study investigated the strength, stiffness and durability of Osorio sand-CFA-lime blends with a variety of improvements by assessing the impact of varying the lime content, fibres, sodium chloride (NaCl) and dry unit weight. Moreover, to contribute to a more rational dosing methodology, strength, stiffness and durability results were correlated to the porosity/binder index [η/(Biv)0.28]. Durability was assessed by comparing wet-dry (WD) and freeze-thaw (FT) cycles, and WD cycles were found to present better performance than FT cycles. Ranks were established for the different components of the blends according to the WD and FT results. The addition of NaCl alone was more effective in improving unconfined compression strength (qu) results than fibres alone. While fibres significantly decreased stiffness at very small-strain shear modulus (G0), NaCl increased G0. The application of η/(Biv)0.28 demonstrated that not only can it predict mechanical behaviour, but also the long-term performance of Osorio sand-CFA-lime blends with or without the addition of NaCl and fibres.

No abstract