Page 59 - New Trends in Green Construction

RENDERING CEMENTITIOUS MORTARS WITH NATURAL FIBERS WASTE
Cinthia Maia Pederneiras, Maria do Rosário Veiga, Jorge de Brito
Keywords: natural fibrer waste, rendering, performance, recycling, mortar 1. Introduction
Fiber-reinforced composites are considered a potential alternative to improve the durability of construction materials. Fibers addition may also increase the deformation capacity and the energy absorption of the rendering. Besides increasing the coating durability, recycled fibers may promote environmental gains.
The incorporation of different kinds of recycled fibers could achieve better performance of cement mortars in terms of cracking resistance and impact strength, without significant decrease in mechanical strength and change in water absorption. The present research investigates cement mortars for non-structural uses, incorporating recycled natural fibers waste. The fibers are from coconut, wool and flax.
2. Materials and methods
The materials used in the experimental programme were: cement, sand and natural fibers waste. The binder used on these mortars was CEM II/B-L 32.5 N. The sand used was previously washed and calibrated.
Two incorporation ratios of recycled fibers waste have been considered, 10% and 20%. This research also studied two lengths of fiber, 15mm and 30mm. All the mortars were produced at the volumetric ratio of 1:4, cement to aggregate.
3. Results and conclusions
The incorporation of natural fibers waste improves properties of the mortars related to cracking resistance and presents a post-cracking binding behavior.
To ensure an adequate workability and to improve the comparability of the mortars the value of consistency was fixed in the range 1405mm. Mortars with incorporation of 10% of fibers (in volume) presented an increase of water/binder ratio to achieve the defined consistency. In contrast 20% of incorporation showed a slight reduction of water/binder ratio.
Fiber-reinforced mortars had a lower bulk density of fresh mortar and dry bulk density of hardened mortar than the control mortar. This could be due to the reduction of the mortars' main constituents.
All modified mortars presented a lower dynamic modulus of elasticity. It can be seen that the reference mortar exhibits higher stiffness. The fibers contribute to a better deformability of the mortar, which leads to a lower risk of failure.
The modified mortars presented an improvement of the mechanical strength, except mortars with coconut fiber that showed a slight decrease in flexural strength. Mortar with 20% of wool fiber
59
New Trends in Green Construction