General relationships controlling loss of mass, stiffness and strength of sustainable binders amended sand

CONSOLI, NILO CESAR; SCHEUERMANN FILHO, HUGO CARLOS; LEON, HELENA BATISTA; DA SILVA CARRETTA, MARIANA; CORTE, MARINA BELLAVER; CORDEIRO, RENAN EDUARDO; CABALLERO, RICARDO DANIEL; LOURENÇO, DAVID EDUARDO

Transportation Geotechnics

Elsevier Ltd

Año: 2021 vol. 27

The idea of using industrial, agrarian, domestic, construction and demolition wastes as sustainable binders substituting Portland cement in stabilization of soils is considered a modern-day concept. The choice of which residues to be used in each specific earthwork is not a simple one, as it largely depends on the distance between where wastes are generated and where they could be used. Material transportation costs may be economically infeasible if the distance is too long. Current research evaluates the potential of pozzolanic wastes studied herein (coal bottom ash - BA, rice husk ash - RHA, ground glass - GG, ground clay brick - GCB), and carbide lime (CL), as possible hydraulic cements (substituting Portland cement) to enhance behaviour of poorly graded sand. Such blends, when compacted, have potential application in construction of stabilized rammed walls, as well as beds of pipelines and spread footings, and as base/subbase of pavements. Pozzolanic reactions occur between silica/alumina in amorphous phases (found in pozzolanic wastes) and Ca++ (existent in CL) in alkaline environments. The amount and type of pozzolan used, the carbide lime content, and the blend porosity affect the loss of mass, stiffness, and strength of compacted sand-pozzolan-CL mixtures. Outcomes have revealed typical normalized tendencies among accumulated loss of mass (ALM) ? porosity/binder index (η/Biv), initial shear modulus (G0) ? η/Biv and unconfined compressive strength (qu) ? η/Biv for the blends, even though each pozzolan has its own distinct characteristics. From a practicing viewpoint, moulding a sand specimen containing given pozzolan and lime amounts, a specific porosity, and cured for a particular time, allows the determination of the curve in which η/Biv controls ALM, G0 and qu for a complete range of porosities and pozzolan and lime contents. Such findings contribute in reducing the quantity of specimens required to be moulded and tested, diminishing earthwork design costs.