Study of mechanical behaviour and shrinkage of mortars reinforced by micro and macro synthetic fibres

Abstract

Shrinkage is a very important phenomenon that affects all concrete structures.If it is not controlled,its effects will be detrimental to the sustainability of the construction.The first objective of this work is to study the mechanical and physical characteristics of the mortar reinforced by synthetic fibres.The second objective is to see if using synthetic fibres reinforcement,playing on their diameter,can improve the mechanical strength and reduce the risk of free shrinkage of these materials.The work is carried out on mortars,with limestone crushing sand,composite cement and synthetic fibres .The fibres used as reinforcement of these mortars are synthetic fibres of polypropylene coming from industrial wastes ;macro fibres with a diameter of 0.45 mm producted by PLAST BROS factory of Bordj Bou Arreridj Algeria and micro fibres of diameter 0.25 mm obtained from the market.The used fibres have the same length of 30 mm.The addition of fibres has a negative effect on the workability of the mixture especially micro fibres.However ,the mechanical properties of mortars have been enhanced.Mortar M100/0 gives the highest compressive strength while mortar M25/75 shows the most important flexural strength.The total shrinkage is decreased with the use of macro and micro fibres ,nevertheless endogenous shrinkage is reduced only by macro fibres.The weight los sis close in all mortars.