Post-fire behavior of structural lightweight concrete designed by Taguchi method

The crack properties and compressive strength of structural lightweight concrete including fly ash exposed to high temperature were investigated. The design of experiments was carried out by Taguchi method using a standard L18 (21 × 37) orthogonal array. The main parameters of experiments were selected as the percentage of fly ash, heating degree, and cement dosage. The mixes containing the three different percentages of fly ash admixtures (0%, 10% and 20%) and two cement dosages (400 kg/m3 and 500 kg/m3) were prepared. After the specimens were exposed to temperatures of 400 °C, 600 °C and 800 °C, the lengths and widths of the concrete cracks were measured using an optical microscope. Finally, the compressive strength tests were carried out. The experimental results for compressive strength, crack width and length were obtained between 5.39 and 38.75, 0.104 and 0.346, 3.48 and 8.538, respectively. The importance of the experimental parameters on compressive strength and crack characteristics was determined by using variance (Anova) method. The anova results showed that heating degree was the most significant effect on compressive strength and crack length, but the most significant effect on crack width was determined as the cement dosage. Furthermore, Taguchi results indicated that the optimum parameters for compressive strength and crack properties of structural lightweight concrete were found as 400 °C, 500 kg/m3 cement dosage and 20% fly ash.