Cohesiveness Of Mortar Research Articles

Addition of Ground Zeolite to Improve the Flowability and Cohesiveness of Mortar

Packing density if of cardinal importantce in the performance of cement-based materials. Theoretically, ground zeolite (GZ), a cementitious material that is finer than cement and coarser than condensed silica fume (CSF), is able to fill the voids between the cement particles in mortar for performance improvement without excessively high specific surface area. In order to evaluate the effects of GZ on flowability and cohesiveness, a total of 15 mortar mixes with different GZ contents and different cementitious materials/aggregate ratios at the same water/cementitious materials ratio were produced for flowability, cohesiveness and strength measurement. Results indicated that adding GZ as no more than 5% cement replacement would increase the flowability and strength, but further addition of GZ to more than 5% decreased the flowability, cohesiveness and strength. The experimental results are in general agreement with the findings from the literatures. Adding GZ tas no more than 5% cement replacement improve both the flowability and cohesiveness at equal-strength basis, further addition of GZ upon 5% improved the concurrent flowability and strength performance when the strength requirement is low, but impaired the concurrent cohesiveness and strength performance. It can be concluded that 5% is optimum GZ addition content in the viewpoint of flowability and cohesiveness performance of mortar.

Roles of water film thickness and SP dosage in rheology and cohesiveness of mortar

Abstract In recent studies, the authors have demonstrated that the combined effects of water content, packing density and solid surface area on the rheology of mortar may be evaluated in terms of the water film thickness (WFT). However, in addition to these factors, the superplasticizer (SP) dosage also has some effects. In order to study the roles of the WFT and SP dosage in the rheology and cohesiveness of mortar, a number of cement–sand mortar samples with different SP dosages and water contents were made for packing density, rheology and cohesiveness measurements. The results showed that the packing density and WFT would increase significantly with the SP dosage. At low SP dosage, the rheology of mortar is dependent on both the WFT and SP dosage while at high SP dosage, the rheology of mortar is dependent solely on the WFT. On the contrary, the cohesiveness of mortar is always dependent on both the WFT and SP dosage. Lastly, regression analysis of the test results was carried out and very good correlations of the measured rheological parameters to the WFT and SP dosage have been achieved.

Effects of CSF content on rheology and cohesiveness of mortar

It is widely known that the addition of condensed silica fume to a concrete mix would improve the cohesiveness and hence segregation stability. However, quite often, this would also impair the flowability. To study the overall effects of condensed silica fume, an experimental programme was launched, whereby 45 mortar samples with different condensed silica fume contents and water/solid ratios, each representing the mortar portion of a concrete mix, were tested for their rheological properties, cohesiveness and packing densities. Their rheological properties were measured in terms of flow spread, flow rate, yield stress and apparent viscosity, while their cohesiveness and packing densities were measured using the sieve segregation and wet packing tests respectively. It was found that the effect of condensed silica fume on flowability could be positive or negative, depending on the water/solid ratio, and when the water/solid ratio is low, the addition of condensed silica fume would improve the flowability by increasing the packing density. It was also found that the effect of condensed silica fume on cohesiveness is always positive. Put together, the overall flowability-cohesiveness performance would be improved by the addition of condensed silica fume.