Impact of waste rockwool on the performance of LC3-based lightweight mortar: A promising solution for greener construction

Abstract

The objective of this study is to explore the influence of waste rockwool (RW) on the mechanical strength and fire resistance performance of high-volume expanded vermiculite (EVM) lightweight mortar made with limestone-calcined clay cement (LC3). LC3 binder was prepared by blending ordinary Portland cement (OPC), metakaolin (MK), and limestone (LS) powder at weight percentages of 40, 40, and 20 wt%, respectively. LC3-based lightweight mortar with a binder-to-aggregate ratio of 1:3 was prepared by replacing 50 vol% of the sand with EVM aggregate. The waste RW was added to the EVM-blended LC3 mortar with different percentages of 1, 3, and 5 % by weight of binder. The compressive strength, flexural strength, drying shrinkage, bulk density, thermal conductivity, fire resistance, and microstructural properties of the hardened LC3-lightweight mortars were determined in accordance with ASTM standards after 28 days of water curing. The results revealed remarkable enhancements in both mechanical and fire resistance performances with RW addition. The addition of 3 wt% RW into the EVM-blended LC3 mortar provided the appropriate enhancement ratios of 56.55 % and 52.83 % in compressive and flexural strengths respectively and increased the fire resistance rating by 25 %. A residual compressive strength of 76.19 % has been maintained after exposure to standard fire for an hour (1 h). The doping of RW into the EVM-blended LC3 mortars led to significant reduction in drying shrinkage rate. A slight, insignificant variation in the thermal conductivity of EVM-blended LC3 lightweight mortar incorporated with RW has been obtained. RW addition resulted in improved microstructure in terms of compactness.