Synthesis of low crystalline thermally insulating calcium silicate hydrate via a simple template-assisted sol-gel method

Internally structured porous calcium-silicate-hydrate (CSH) particles were made by a simple template-assisted sol-gel process involving an inexpensive and renewably produced templating material (skimmed natural rub-ber (NR), a waste generated during production of concentrated rubber latex) and a cheap silica source (sodium silicate). The CSH particles were then added to cement to produce mortar with excellent thermal insulation performance. Effects of the following factors on morphology, porosity, crystallinity and thermal insulation performance of CSH and CSH-mortar were studied: the CSH synthesis parameters (time and temperature for hydrothermal aging; the NR/silica mass ratio) and CSH/cement mass ratio in mortar. The CSH particles produced were mainly amorphous. The tobermorite and truscottite phases developed as both the time and temperature of hydrothermal aging were increased; however, a high value of NR/silica mass ratio hindered crystallization. Irrespective of the presence of crystalline phases, CSH particles improved the thermal insulation performance of mortars. The crystallization affected the meso-and macropores within the CSH solids and contributed to enhancing their thermal insulation performance. The NR template was crucial to develop the porous structure that enhanced the thermal insulation performance of CSH and the mortar incorporating it.

Automated summary

Internally structured porous calcium-silicate-hydrate (CSH) particles were synthesized using a simple sol-gel process with a template from waste natural rubber and a cheap silica source. The CSH particles improved the thermal insulation performance of mortars, regardless of the presence of crystalline phases. The use of the natural rubber template was crucial in developing the porous structure and enhancing the thermal insulation performance of CSH and mortar.