Recyclability, durability and water vapour adsorption of unstabilised and stabilised compressed earth bricks

Agostino Walter Bruno,Yann D’Offay-Mancienne,Céline Perlot,Blake Scott

doi:10.1617/s11527-020-01585-7

Agostino Walter Bruno, Yann D’Offay-Mancienne + Show 2 more

Open Access

https://doi.org/10.1617/s11527-020-01585-7

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Abstract

This paper investigates the recyclability, liquid water durability and water vapour adsorption of both unstabilised and stabilised compressed earth bricks. Stabilised bricks were manufactured by adding either cement or the biopolymer guar gum to the base earth. Unconfined compressive strength tests were then performed on both unstabilised and stabilised earth bricks manufactured with recycled material (i.e. material taken from the failed compressed earth bricks after the compressive strength tests). These tests enabled to assess the influence of recycling on the stiffness, strength and strain energy of all compressed earth bricks. Immersion and drip tests were subsequently performed to investigate the effect of cement and biopolymer stabilisation on the durability of the compressed earth bricks against the weathering action of water. An additional set of laboratory experiments was finally conducted by means of a Dynamic Vapour Sorption (DVS) system to study the effect of earth stabilisation on the capacity of adsorbing/releasing water vapour as the ambient humidity changes. Outcomes from this experimental campaign showed that both unstabilised and biopolymer stabilised earth bricks maintained a similar mechanical performance after recycling, while cement stabilised bricks showed a remarkable reduction of both stiffness and strength. Finally, both cement and biopolymer stabilised bricks improved the liquid water durability while reducing the water vapour adsorption compared with the unstabilised earth bricks. Results from this experimental work will be useful for life cycle assessments, especially for modelling the end-of-life of the material as well as its potential reuse.

Highlights

The adoption of the earth in mainstream construction is recently gaining the interest of engineers, architects and material scientists because of its eco-friendly credentials
The effect of earth stabilisation and recyclability was investigated by means of compressive strength tests performed on three samples for each brick composition
After recycling, unstabilised earth bricks showed an almost identical compressive strength, suggesting that this material can be recycled multiple times without any loss of mechanical performance. This is because the mechanical behaviour of unstabilised samples depends on the capillary pressure [53, 54], which in turn is dependent on temperature, relative humidity and pore size distribution inside the material

Summary

Introduction

The adoption of the earth in mainstream construction is recently gaining the interest of engineers, architects and material scientists because of its eco-friendly credentials. Stabilisation is deemed to reduce both the hygrothermal regulator capacity and the full recyclability compared with the unstabilised earth, limiting its environmental performance over the entire life cycle [5, 8]. These considerations on the complete recyclability of unstabilised earth materials and the detrimental effect of stabilisation are generally based on assumptions, whereas a systematic experimental investigation on this subject is missing from the literature. The main objective of these studies was to demonstrate that the recycled earth materials still have suitable geotechnical properties for earth construction in agreement with existing recommendations. These studies did not show whether the resulting mechanical performance of the recycled earth matches that of the original material and whether the recycling process has induced any deterioration of the material

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