Energy savings, thermal conductivity, micro and macro structural analysis of fired clay bricks incorporating cigarette butts

In this study, lightweight structural bricks incorporating various percentages of cigarette butts (CBs) are produced to investigate the thermal properties, energy savings, porosity and micro- and macro-structure. A novel method was developed to monitor the energy consumption of the furnace during the firing process, and Scanning Electron Microscopy (SEM) and X-ray micro-Computed Tomography (micro-CT) imaging were used to characterize the quantity, distribution, size, and shape of the micro- and macro-scale pores of the brick samples incorporating CBs. The energy savings of the microporous bricks with 1% CBs by weight (wt.) varied between 8% (theoretical value) and 10.2% (measured value). Clay bricks showed an increase in porosity and a decrease in density with the increase in CB content, which reduced thermal conductivity. Thermal conductivity was measured to reduce from 0.463 to 0.347 W m−1 K−1 with the addition of 2% CBs by wt. compared to the control bricks. The 3D models of the bricks incorporating various percentages of CBs demonstrated a homogenous distribution of pores within the brick structures. On a micrometer scale, the size of the micro- and macro- pores varied within a range of 0.035 to 1.365 mm.