Paperbricks produced from wastes: modeling and optimization of compressive strength by response surface approach

The high cost of building materials occasioned by the increased cost of constituent materials has contributed immensely to the problem of housing deficit faced in Africa and major developing countries of the world. Waste paper can be recycled into bricks but there are limited studies to that effect. Waste glass is used as partial cement replacement to reduce the cost of cement and is also used as a pozzolan. This study focused on the development of paperbricks from the wastes of paper and glass. Response surface method (RSM) was involved in the design of the experiment involving 4 factors: glass powder replacement of cement (A), curing duration (B), compaction pressure (C), and water/cement ratio (D). Box-Behnken method was engaged for the 4-factor, 3-level design. The result of ANOVA showed that experimental inputs had a significant effect on compressive strength response. Factors A, B, and C had a synergetic effect on the response while factor D had an antagonistic effect on the response. Combined interaction between the factors that the response depended on the interactive patterns of the factors. A statistical fit model was developed to predict the compressive strength of the composite. RSM optimization revealed a combination of 36.68%, 57.82 days, 8.50 MPa, and 0.364 for factors A, B, C, and D, respectively, predicting a strength value of 7.358 MPa. Validation experiment carried out using the optimal conditions yielded 7.54 MPa; a deviation of + 0.0247. Since the deviation is less than ± 0.05, the model was statistically validated and fit.