Mixed Proportion Design of Lightweight Concrete Using the Sludge Kilned Coarse Aggregate from Reservoir

Abstract

The sludge dramatically causes the water pollution and storage reduction of a reservoir, threatening its functionality and operational life span. One strategy is to add sludge into lightweight concrete, thus, recycling the sludge and making it one of the valuable natural resources. This study intends to use the Design of Experiment (DOE) and Taguchi Method to ensure the stability of quality and to reduce the production cost of lightweight concrete using the sludge kilned coarse aggregate from the Shihmen reservoir in Taiwan. Based on literature reviews as well as past experimental results, the research selects four control factors including lightweight aggregate unit weight, water content, water-binder ratio (W/B), and interactions among these factors. By using Analysis of Variance (ANOVA), this study discusses the significant degree of these control factors and their interactions, affecting the quality characteristics of lightweight concrete such as compressive strength, ultrasonic wave, and electric resistance at different ages. The significant levels and contribution ratios from each ANOVA analysis are placed in a Cross Table to obtain the overall evaluation, giving the optimal mix proportions. On the basis of the results, the optimal parameter setting are: the unit weight of lightweight aggregate at 0.378 g/cm3, the water consumption at 160 kg/m3, and the water-binder ratio at 0.28 for the 14 and 28-day age lightweight aggregate concrete, and the unit weight of lightweight aggregate at 0.378 g/cm3, the water consumption at 140 kg/m3, and the water-binder ratio at 0.28 for the 91-day age. Furthermore, considering the mean and variance, the research find out the optimal design according to the combination of ages and quality characteristics using the Type III Signal to Noise Ratio of Taguchi’s nominal-is-the-best quality characteristics. The obtained result includes the unit weight of lightweight aggregate at 0.378 g/cm3, the water consumption at 160 kg/m3, and the water-binder ratio at 0.28.