Preliminary study on valorization of scraps from the extraction of volcanic minerals

Federica Piccolo1, Federica Gallo1, Fernanda Andreola1, Isabella Lancellotti1, Bruno Maggi2, Luisa Barbieri1,3

1 Department of Engineering Enzo Ferrari , University of Modena and Reggio Emilia, Via P. Vivarelli 10/1, 41125, Modena, Italy
2 EuroPomice srl, Via Napo Torriani 1, 20124, Milano, Italy
3 Interdepartmental center for applied research and services in advanced mechanics and motoring, INTERMECH-Mo.Re., Via P. Vivarelli 10/1, 41125, University of Modena and Reggio Emilia, Modena, Italy

Abstract


Powders < 3mm of pumice and lapillus (quarry scraps of national volcanic minerals) were employed in the tailoring and characterization (from the physical, chemical and mechanical point of view) of geo-polymers and lightweight aggregates. Geo-polymers were obtained at room temperature by substituting 70 - 80 wt% of metakaolin by volcanic scraps and employing an alkaline solution with a Na2SiO3/NaOH ratio from 0.8 to 1 for pumice and lapillus series, respectively. Within 24 h and in water, bulk specimens resulted with good integrity, with pH values around 9-11 and conductivity increasing over time, but less for the lapillus-containing sample richest in metakaolin indicating more compactness. The porosity, ranging around 32-33% for all the samples, increased up to 45% for the formulation based on 80% of lapillus. The best mechanical performance was achieved by lapillus samples: compressive strength in the range 35-38 MPa against 6-8 MPa of pumice ones. Lightweight aggregates were created by powder sintering at 1000 C for 1 hour of 85 wt% of volcanic scraps and 15 wt% of spent coffee grounds used as pouring agent. Additional formulations were realized adding 50 wt% of nourishing mixture P and K-containing in the form of animal bone meal and vegetable biomass ashes. The specimens resulted porous and light (porosity around 60%), with good capacity of water retains, and, except in two cases, with neutral pH and conductivity values below 2 mS/cm, indicating a possible use for substrate (growing layer) in roof gardens, green roofs, house gardens, etc..

Keywords


geo-polymers; lightweight aggregates; quarry scraps; recycling

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