Optimization of saw dust ash and quarry dust pervious concrete's compressive strength using Scheffe's simplex lattice method

This study presents optimization of mechanical properties of quarry dust (QD) and saw dust ash (SDA) blended pervious concrete for sustainable road pavement construction with Scheffe's (5, 2) simplex lattice design. This research will offer opportunity for the re-use and reutilization of waste materials to control indiscriminate waste disposal which endanger our environment and to achieve eco-friendly and sustainable green construction materials. The method provides analytical approach for factor levels optimization of a mixture design problem in respect of the response parameters whereby the number of model terms to be developed is influenced by the total number of components and the order of regression polynomial to fully explore the factor space. Laboratory works were carried out using the Scheffe's formulated mixture ratios to evaluate the concrete's strength properties after 28 days of hydration. According to the results of the optimization exercise and the derived responses, the maximum compressive strength is 21.71 MPa with a mix proportion of 0.55:0.8:0.25:3.55:0.2 for water, cement, QD, coarse aggregate, and SDA, respectively. However, minimum compressive response of 16.58 MPa was obtained with a mix proportion of 0.435:0.95:0.1:1.55:0.05 for water, cement, QD, coarse aggregate, and SDA, respectively. Furthermore, the mathematical model developed was statistically validated based on the results of analysis of variance and Student's t test at 95% confidence interval. Hydraulic conductivity tests were then performed on the sample mixes at the five vertices of Scheffe's factor space, and the results showed a linear increase in the hydraulic conductivity value as the ratio of SDA and QD increased, indicating that the cavity content of the pervious concrete mixtures proliferates with minimum SDA and QD content of 2.833% and 3.683%, respectively. Spectrum electron microscopy and energy-dispersive X-ray (EDX) were also used to investigate the mineralogical and morphological constituents of pervious concrete samples with varying admixture mixture compositions. However, due to changes in the fabrics of the concrete mixture, boosted by the cementitious composites development such as calcium silicate hydrate and calcium aluminate hydrate, the cement-admixtures blend aided the concrete matrix in forming porous microstructures and enhanced its mechanical and permeability properties for road pavement applications.

Automated summary

This study optimizes the mechanical properties of blended pervious concrete using quarry dust (QD) and saw dust ash (SDA) for sustainable road pavement construction. It provides an analytical approach for the optimization of factor levels and explores the factor space of the mixture design problem. The laboratory experiments show that the maximum compressive strength of the concrete is 21.71 MPa, while the minimum compressive strength is 16.58 MPa. Hydraulic conductivity tests indicate that the cavity content of the concrete mixtures increases as the ratio of SDA and QD increases.