The paper investigates the second-order interactions of parameters in an alkali-activated mixture of paper production waste (PPW) and blast furnace slag (BFS) in Taguchi method. The PPW including lime mud (LM) and paper sludge (PS). This paper provides the experimental models to assess the compressive and flexural strength of them at 7-day and 28-day. The results have shown that the second-order interactions between PPW and alkali-activated activator exists in each experimental model, and the significant interactions affect the selection of optimal compositions. Compared with the interactions between the PPW themselves, the interactions between PPW and alkali-activated parameters are the main significant factors affecting its physical properties. In each experimental model, the maximum compressive strength was 47.41 MPa in 7-day and 65.64 MPa in 28-day. Compared with the confirmatory experiments, the deviation of prediction calculated by experimental models was 3.08% and 0.56%, respectively. The maximum flexural strength was 5.74 MPa in 7-day and 5.96 MPa in 28-day; compared with the confirmatory experiments, the deviation of prediction calculated by experimental models was 5.40% and 0.17%. Considering the influence of circular materials, 30% of PPW should be a suitable ratio to replace BFS as the raw material of alkali-activated slag (AAS).

Waste recycling has always been a priority in the paper industry. In this study, the potential of translating various wastes in papermaking into building materials was separately evaluated. For the first time, the improvement of flexibility and sample texture after translating wastes into cementitious materials was analyzed. The results showed that 20% of the waste in alkali-activated slag slurry is the best proportion for papermaking. In addition, paper sludge and wood chips significantly improved the slurry flexibility while lime mud and bottom ash did not have this effect. Considering the effect of adding wood chips on the optimization of the sample texture, the most appropriate proportion of the paper sludge was 5% when the wood chips in the mixture were 15%. The most suitable alkali equivalent was 6%, with a silicate modulus of 0.9. According to the experimental results, wastes in papermaking had great potential for exploitation and application as circular materials.

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