Structural and mechanical studies of a ground-granulated blast-furnace slag (GGBS) based binder and its use in earth concrete

Abstract

The aim of this work is to characterize the mechanical properties with the understanding of the chemical reactions of a ground granulated blast-furnace slag (GGBS) based binder for earth concrete. Both binder paste and earth concrete samples are cured at 20 °C and 100% of relative humidity. Several characterization techniques are conducted, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (ATR-FTIR) and mechanical tests. The compressive tests are done at 7, 28 and 90 curing days. This study shows that dicalcium silicates found in the binder powder leads to calcium silicate hydrates (C-S-H) formation in the early age. It also reveals the presence of portlandite, leading to the calcium-activation of the GGBS. This latent reaction creates several phases such as C-S-H and C-A-H in the mid and long term. The analyzis of the infrared specters corroborates those results. The C-S-H characteristic bands are identified around 400, 655 and 960 cm-1. C-A-H characteristic peak is identified at 850 cm−1. The mechanical study shows that the compressive strength of the binder reaches 13.9±0.3 MPa, 21.1±0.8 MPa and 25.4±0.7 MPa and the earth concrete 8.9±0.7 MPa, 16.6±0.3 MPa and 18.7±0.2 MPa at 7, 28 and 90 curing days respectively. Those mechanical properties are brought by the hydrates formed during the binder’s reaction. It creates a matrix that bounds the grains of raw earth together. This work highlights the high mechanical properties of earth concrete made out of this binder. It also shows the potential of calcium-activated GGBS and pozzolanic reactions in order to create low carbon earth concrete with good resistance. Such binder may foster the use of earth concrete in buildings, enhancing their thermal comfort and energy efficiency while reducing their environmental impact.