Abstract
There is an increasing need to identify the effect of mix composition on the rheological properties of composite cement pastes using simple tests to determine the fluidity, the cohesion and other mechanical properties of grouting appli- cations such as compressive strength. This paper reviews statistical models developed using a fractional factorial design which was carried out to model the influence of key parameters on properties affecting the performance of composite ce- ment paste. Such responses of fluidity included mini-slump, flow time using Marsh cone and cohesion measured by Lombardi plate meter and unit weight, and compressive strength at 3 d, 7 d and 28 d. The models are valid for mixes with 0.35 to 0.42 water-to-binder ratio (W/B), 10% to 40% of pulverised fuel ash (PFA) as replacement of cement by mass, 0.02 to 0.06% of viscosity enhancer admixture (VEA), by mass of binder, and 0.3 to 1.2% of superplasticizer (SP), by mass of binder. The derived models that enable the identification of underlying primary factors and their interactions that influence the modelled responses of composite cement paste are presented. Such parameters can be useful to reduce the test protocol needed for proportioning of composite cement paste. This paper attempts also to demonstrate the usefulness of the models to better understand trade-offs between parameters and compare the responses obtained from the various test methods which are highlighted. The multi parametric optimization is used in order to establish isoresponses for a de- sirability function of cement composite paste. Results indicate that the replacement of cement by PFA is compromising the early compressive strength and up 26%, the desirability function decreased.
Highlights
There has been a growing interest in the use of cement paste containing viscosity enhancer admixture (VEA) admixture for repairs, injection, embedding of anchors and post-tensioning, rock and oil-well grouting
Cement-based pastes are widely used in injection grouting of cracks in massive structures since their physical and mechanical properties can be controlled. This is assured by judicious choice of the type and fineness of cement, water-to-binder ratio, chemical and mineral admixtures [1]
The main objective of this study is to evaluate the effect of the water-to-binder ratio, the pulverised fuel ash (PFA) content, the dosages of SP and VEA on the rheological properties and compressive strength at 3 d, 7 d and 28 d of composite pastes using statistical design approach and analysis of experiments [10, 11]
Summary
There has been a growing interest in the use of cement paste containing VEA admixture for repairs, injection, embedding of anchors and post-tensioning, rock and oil-well grouting. A cement-based paste should be stable enough to reduce sedimentation, bleeding, and water dilution. Cement-based pastes are widely used in injection grouting of cracks in massive structures since their physical and mechanical properties can be controlled. This is assured by judicious choice of the type and fineness of cement, water-to-binder ratio, chemical and mineral admixtures [1]. The incorporation of one or more types of supplementary cement replacement materials (CRMs) such as pulverised fuel ash having different morphology and grain-size distribution values can improve particle size distribution and packing of solid particles, enhancing fluidity, stability and permeability. Improvements in the quality and uniformity of CRMs and the attention given to admixture formulations have greatly assisted progress
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