School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK


The development of new products, in this case a range of novel masonry units possessing properties which match or exceed current existing coarse aggregate concrete block products, is conventionally performed within a laboratory. However, laboratory based experimental optimisation can result in many thousands of samples being produced; this is a time consuming, costly and often a laborious process. This paper examines whether it is possible to utilise mathematical modelling, in particular the HyperStudy 9.0 software, to reduce the amount of experimental data required and hence produce a more economical approach to optimisation within a laboratory.

From the experimental optimisation alone, the optimal compressive strength (35.82MPa) of the new unit was obtained from a mix containing 30% coarse aggregate and compacted at a pressure of 24MPa. Mathematical modelling using only half of the experimentally obtained data predicted that a coarse aggregate content of 31.95% and a compaction pressure of 21.73MPa would provide an optimum compressive strength of 35.95MPa. Mathematical optimisation can therefore improve the efficiency and economy of laboratory investigations and potentially provide economies during future scaling-up and manufacturing processes i.e. in this case, reduce compaction pressures.

Key words
Masonry units; Bitublock; Recycling; Waste materials; Incinerator bottom ash; Crushed glass; Pulverised fuel ash; Incinerated sewage sludge ash; Empirical model building; Optimisation