ECC Design Based on Uniform Design Test Method and Alternating Conditional Expectation

Xiaoqin Li,Xiao Yang,Xi Du,Zude Ding,Jincheng Wen

doi:10.1155/2019/9575897

Abstract

Engineered cementitious composites (ECC) have higher ultimate tensile strains than normal concrete. The mechanical properties of ECC strongly depend on raw materials and the mix proportions. The uniform design test method and alternating conditional expectation, which is a nonparametric regression analysis method, were used to design the ECC mix proportion. According to the regression analysis, the optimized W/B, S/B, and F/B ranges could be obtained as 0.35–0.42, 0.25–0.3, and 0.02, respectively. The tested proportions for validation were randomly adopted within the range of W/B, S/B, and F/B. The uniaxial compression, tension, and four-point bending tests were conducted to verify the material behaviour of the designed ECC. Results showed that all the specimens had large ultimate tensile strains and high fracture energy capacities, and strain hardening was also observed. The fibers were found to be uniformly distributed in the specimens by using a scanning electron microscope. This paper may provide theoretical and practical guidance for the ECC and other cement-based material mix proportion design.

Highlights

Concrete is widely used in civil engineering
Polyvinyl alcohol (PVA) fibers showed a great improvement for ultimate tensile strain εcu, and fracture energy GIF compared with the cement matrix without fibers
MATLAB was used to randomly select five Engineered cementitious composites (ECC) mix proportions within the range of the optimized mix proportion, which are listed in Table 14. e tests were performed to verify whether the range of the mix proportion in Table 13 has a high ultimate tensile strain εcu and fracture energy GIF. erefore, the ECC uniaxial tensile tests were chosen as the verification tests. e four-point bending tests were performed to determine the behavior of the ECC slab with the optimized mix proportion

Summary

Introduction

Concrete is widely used in civil engineering. concrete is brittle, and its toughness decreases with its increasing strength, which may lead to cracking in structures [1,2,3]. Nonlinear transformations are mostly used in alternating conditional expectations to maximize the correlation between θ(A) and φ1(x1) + · · · + φs(xs) based on the data feature of the combinative table X(xij) and test result table Y(yij). Because the number of factors is three, according to the application Table 5, columns 1, 5, and 6 of the uniform Table 4, representing fly ash/cement mass ratio, water-cement ratio, and fiber/cement mass ratio, were used in the test design. E uniform-designed ECC mix proportions could be obtained using equation (3) and listed, and the tests were performed . The specimens were stored in the standard curing room for 28 days

Uniform Design Specimen Tests

Verification Tests

Conclusions