Issue 43

S. Jing et alii, Frattura ed Integrità Strutturale, 43 (2018) 33-42; DOI: 10.3221/IGF-ESIS.43.02 36 K — 2 =K 2 /3=147.2/3=49.0 (5) K — 3 =K 3 /3=136.6/3=45.5 (6) The size of the range R is introduced to measure the impact of factors on the test indices. The importance of a factor is positively correlated with the size of its range. If a factor has a big range, any variation in the level of the factor will significantly affect the test indices, and the inverse is true. The size of the range R is calculated as follows: R ＝ ( K — i ) max -( K — j ) min ＝ 49.0-45.5 ＝ 3.5 (7) The range of other factors is calculated in the same way. The results are listed in Table 2. Test Group A Fly Ash Content B Sand-binder Ratio C Water- binder Ratio D Plasticizer Content Compressive Strength (MPa) Z1 1(0.9) 1(0.30) 1(0.20) 1(0.40%) 55.3 Z2 1(0.9) 2(0.33) 2(0.23) 2(0.70%) 47.4 Z3 1(0.9) 3(0.36) 3(0.26) 3(1.00%) 39.9 Z4 2(1.2) 1(0.30) 2(0.23) 3(1.00%) 47.3 Z5 2(1.2) 2(0.33) 3(0.26) 1(0.40%) 38.5 Z6 2(1.2) 3(0.36) 1(0.20) 2(0.70%) 61.4 Z7 3(1.5) 1(0.30) 3(0.26) 2(0.70%) 37.9 Z8 3(1.5) 2(0.33) 1(0.20) 3(1.00%) 55.4 Z9 3(1.5) 3(0.36) 2(0.23) 1(0.40%) 43.3 K 1 142.6 140.5 172.1 137.1 K 2 147.2 141.3 138.0 146.7 K 3 136.6 144.6 116.3 142.6 K — 1 47.5 46.8 57.3 45.7 K — 2 49.0 47.1 46.0 48.9 K — 3 45.5 48.2 38.7 47.5 R 3.5 1.4 18.6 3.2 Table 2 : Orthogonal experiment result of compressive property. As can be seen in Table 2, for the four factors considered in the experiment, the range in decreasing order is: water-binder ratio, fly ash content, plasticizer content and sand-binder ratio. The range of the water-binder ratio is 18.6, which is far greater than the range of the other three factors. This result indicates that the water-binder ratio has the greatest influence on the compressive strength of ECC, followed by fly ash content, plasticizer content and sand-binder ratio. In order to further analyze the impact of each factor on the compressive strength, a relationship curve diagram was drawn, taking the change of each factor as an abscissa and the average compressive strength K — i as an ordinate. According to the results of the range analysis and Figure 2: 1) The water-binder ratio is the key factor in the compressive strength of high toughness cementitious composites, and the strength increases with the decrease of the water-binder ratio. If the water-binder ratio is too large, the internal porosity of the material will increase, which can directly lead to lower compressive strength. 2) In the experiment, the mass ratio of fly ash to cement is in the range of 0.9 - 1.5. The compressive strength increases first and decreases later with increasing fly ash content. Fly ash is made up of a large number of subtle spherical vitreous compositions with fine particle size, which can play a role in improving the mobility of the mixture. Meanwhile, there is the Pozzolanic Effect of fly ash, namely the chemical reaction of fly ash and cement hydrate. The products of the chemical reaction are often filled in the pores of the cement hydrate, reducing the interior porosity of the mixture and improving the compactness of the material. However, the active effect of fly ash should lag behind the hydration reaction