Improving the workability and rheological properties of Engineered Cementitious Composites using factorial experimental design

Abstract

In the development of Engineered Cementitious Composites (ECC), micromechanics-based design theory is adopted to properly select the matrix constituents, fiber, and fiber-matrix interface properties to exhibit strain hardening and multiple cracking behaviors. Despite the micromechanics design constraints, practical applications show that the workability and rheological properties of matrix can affect the fiber dispersion uniformity, which have also direct concerns on composite mechanical properties. For this reason, in this research, parameters of micromechanics-based optimized ECC mixture design, which most possibly affecting the workability and rheological properties, are investigated. An experimental program that contains 36 different ECC mixtures was undertaken to quantitatively evaluate the combined effects of the following factors on workability and rheological properties: water-binder (w/b), sand-binder (s/b), superplasticizer-binder (SP/b) ratios and maximum aggregate size (Dmax). A mini-slump cone, a Marsh cone and a rotational viscometer were used to evaluate the workability and rheological properties of ECC mixtures. Compressive strength and four point bending tests were used for mechanical characteristics of ECC mixtures at 28 days. The effects of studied parameters (w/b, s/b, SP/b and Dmax) were characterized and analyzed using regression models, which can identify the primary factors and their interactions on the measured properties. Statistically significant regression models were developed for all tested parameters as function of w/b, s/b, SP/b and Dmax. To find out the best possible ECC mixture under the range of parameters investigated for the desired workability and mechanical characteristics, a multi-objective optimization problem was defined and solved based on the developed regression models. Test results indicate that w/b, s/b and SP/b parameters affect the rheological and workability properties. On the other hand, for the range of studied aggregate sizes, Dmax is found to be statistically insignificant on the rheological and workability properties of ECC.Scientific and Technical Research Council of Turkey (MAG-108M495

Experimental and Predictive Mechanical Strength of Fiber Reinforced Cementitious Matrix (Frcm)

“…Also, Maruthachalam et al [19] and Sahmaran et al [27] used statistical tools to test the properties of fiber reinforced high performance concrete (FRHPC), and developed regression models using Analysis of Variance which adequately fit the experimental data with p<0.05.…”

Prediction of Mechanical Properties of Cold Rolled Steel Using Genetic Expression Programming

“…The F value in Table II provides an information of the degree of contribution of the independent parameters to the measured dependent parameter (test results). If the F is high, the contribution of the factors to that particular response is high [8,9]. This analysis was carried out for a level of confidence of 90% i.e., for a level of significance of 10%.…”

Strength Modeling of Mechanical Strength of Polyolefin Fiber Reinforced Cementitious Composites

“…Also, the effect of the independent variable, RI, on each of the dependent variables, FS, IIEA and UIEA are evaluated in as the significant models [14]. For Models 1 and 2 representing CS and TS respectively, the R 2 of 0.976 and 0.847 suggest that both the independent variables, CP and RI jointly predict the CS and TS of PL-FRCC and explains 97.6 and 84.7 per cent of the variations in CS and TS respectively.…”

“…The regression model proposed in the present study will be helpful to predict the strength of FRCC, and accordingly vary the input parameters or the matrix design. In order to arrive at the best set of predictors of a particular dependent variable [14,47], the objective of the present study is to develop linear regression equations using SPSS [48] to evaluate the effect of fiber percentage and/or curing days on the mechanical strength of FRCC.…”

“…Cavdar (2012) [12] used polypropylene (PP), carbon (CF), glass (GF) and polyvinyl alcohol (PVA) fibers in five different ratios 0%, 0.5%, 1%, 1.5% and 2% by volume and determine the flexural strength and ductility properties of cementitious composites (mortar) under high temperature. Some authors (like Ahmed et al, 2007) [13] have used 2.5% fibers but it is advisable to restrict the fiber volume to 2% to avoid workability problems during preparation of fibrous mortar, and some adjustments in matrix design is needed [14,15]. PVA fibers have replaced asbestos fibers in cement boards and are widely used in engineered cementitious composites (ECC) such as road and deck slab outlays, tunnel lining, and secondary slabs, and other applications using shotcreting methods [16].…”