Workability of biopolymer modified aerial lime mortars studied by traditional and rheological approaches

Workability of biopolymer modified aerial lime mortars studied by traditional and rheological approaches

en

In the building industry mainly cellulose-based viscosity modifying admixtures are used to improve the properties of concrete and dry-mix mortars. Lately the alternative biopolymers, previously used in different industries, have been tested for applicability especially in self-compacting concrete. These admixtures vary in the polymeric structure, types of functional groups, thus also in efficiency and even slightly in working mechanisms. In this work, variations of the behaviour of aerial-lime based mortars prepared with the same workability defined by flow value were studied. Mortars with three different flow values were prepared for each mixture altering only the water:binder ratio. Apart from flow table value the plunger penetration depth was also studied as another representative of traditional and simple methods. The mortars were subjected torheological testing using hybrid rheometer. The flow characteristics and viscoelastic properties of the mortars in the initial state were monitored.The plunger penetration depth results copied the flow table values in trend but with non-linear dependency, which is more apparent within higher doses of admixtures. Most of the mortars showed rheopectic behaviour, only the most water-demanding admixtures such as diutan gum, hydroxypropyl guaran, and hydroxypropylmethyl cellulose promoted the thixotropy of the mixtures. The length of linear viscoelastic region (LVR) decreased with growing flow table value and also some of the admixtures notably shortened the LVR especially for the low flow value. For admixtures with reported stabilizing properties, the value of modulus crossover was specific for each dosage and the varying flow value.Noticeable differences in the efficiency and dosage-dependency of the admixtures were observed, mainly for water consumption and viscoelastic properties of the mortars. The diutan gum and hydroxypropyl guaran were found the most competitive to the cellulose ethers.

In the building industry mainly cellulose-based viscosity modifying admixtures are used to improve the properties of concrete and dry-mix mortars. Lately the alternative biopolymers, previously used in different industries, have been tested for applicability especially in self-compacting concrete. These admixtures vary in the polymeric structure, types of functional groups, thus also in efficiency and even slightly in working mechanisms. In this work, variations of the behaviour of aerial-lime based mortars prepared with the same workability defined by flow value were studied. Mortars with three different flow values were prepared for each mixture altering only the water:binder ratio. Apart from flow table value the plunger penetration depth was also studied as another representative of traditional and simple methods. The mortars were subjected torheological testing using hybrid rheometer. The flow characteristics and viscoelastic properties of the mortars in the initial state were monitored.The plunger penetration depth results copied the flow table values in trend but with non-linear dependency, which is more apparent within higher doses of admixtures. Most of the mortars showed rheopectic behaviour, only the most water-demanding admixtures such as diutan gum, hydroxypropyl guaran, and hydroxypropylmethyl cellulose promoted the thixotropy of the mixtures. The length of linear viscoelastic region (LVR) decreased with growing flow table value and also some of the admixtures notably shortened the LVR especially for the low flow value. For admixtures with reported stabilizing properties, the value of modulus crossover was specific for each dosage and the varying flow value.Noticeable differences in the efficiency and dosage-dependency of the admixtures were observed, mainly for water consumption and viscoelastic properties of the mortars. The diutan gum and hydroxypropyl guaran were found the most competitive to the cellulose ethers.