Feasibility study of lightweight cement composite containing flax by-product particles: Physico-mechanical properties

The purpose of this study was to investigate the potential utilisation of flax by-products in cementitious matrices, as aggregate additives, to develop lightweight construction materials that could be used for load-bearing walls. A material containing different amounts of flax particles, ranging from 0% to 10% as partial replacement of cement, was aerated by artificially entrapping air voids by means of a protein air-entraining agent. The composites were characterised by destructive and non-destructive testing. Analyses were made regarding the inhibitory effect of flax particles on hydration of cement, and the properties of the fresh and hardened composite. The results of hydration test have shown that an increase of flax particles in the cement matrix increases the inhibitory effect on cement hydration with a long setting time of the composite. For a specific mix with 10% of flax particles replacement, the corresponding inhibitory index-value of 57.5% classifies the mixture as being of “high inhibition”. However, the use of calcium chloride reduced the inhibitory effect on cement hydration, resulting in a “low inhibition” classification. Results from tests performed on fresh composite have shown attractive properties such as improvements in workability and air-entrainment with increasing flax particles. Study of the hardened composite obtained from oven dried specimens has indicated a significant reduction in sample unit weight, along with compressive strengths compatible with the basic requirement of lightweight construction materials, corresponding to RILEM “class III” recommendations. The reduction in flexural strength was lower than that in compressive strength. The results have also shown a high reduction in the dynamic elastic modulus, which indicates a high level of sound insulation of the composite.