Investigation of the mechanical behaviour of metakaolin-based sandcrete mixtures

Abstract

This paper investigates the mechanical properties of sandcrete mixes with metakaolin (MK) as a mineral additive. Three different types of binders were prepared: one used as reference, based on 100% w/w ordinary Portland cement (PC), and two modified, where MK replaced PC in percentages 10% or 20% by weight of the reference cement content. Experimental tests have been carried out in order to obtain the full stress–strain diagram for the material under uniaxial compressive loading. The results of the tests have been post-processed numerically in order to obtain various mechanical characteristics of the sandcrete material, such as compressive strength, modulus of elasticity and strain at maximum strength. It has been found that, in general, specimens with metakaolin in the binder exhibit enhanced compressive strength compared to the reference samples without metakaolin. The improvement in compressive strength was more pronounced in samples with higher concentration of binder (50% w/w) and low or medium water per binder (W/B) ratio. Samples with higher compressive strength were characterised by higher values for the measured ultrasonic pulse velocity. The strain values, recorded at maximum strength, are considerably higher than the strain value of 2‰ for concrete under uniaxial compressive load.

Keywords:

• sandcrete
• mineral additives
• metakaolin
• mechanical properties
• ultrasonic pulse velocity

Acknowledgements

The authors would like to express their special thanks to TITAN Cement Company S.A. for the free supply of cement as well as to Imerys Minerals Ltd for providing the amounts of metakaolin used in this work. The authors would also like to express their gratitude to Mr Ch. Psaromichelakis, Mr M. Frantzis, Mr I. Karampampas, Mr P. Kalantzakis and Mr V. Christopoulos for their assistance on the preparation of samples and also to Dr Ch. Leptokaridis and Dr D. Fragoulis from TITAN Cement Company S.A. for the compressive strength and the XRD tests of samples, respectively.