Effect of pre‐coating lightweight aggregates on the self‐compacting concrete
Mir Yashar Vahabi, Behzad Tahmouresi, Hossein Mosavi, Siavash Fakhretaha Aval
Abstract
Abstract The porous lightweight aggregates adversely affect fresh properties of concrete, including slump and disruption of pumping concrete. Besides, this type of concrete is very susceptible to shrinkage cracking. In this study, two types of lightweight aggregates were used with a combination of two types of coating, including hydrophobic polymers ‐polyvinyl acetate and styrene‐butadiene rubber coatings. The coatings were applied in single and double layers. For the fresh concrete, the fresh properties of concrete, including slump flow, T 50 , flow time, and L‐Box were evaluated and for the hardened concrete, compressive strength, flexural strength, tensile strength, water absorption and shrinkage was studied. It was seen that the slump flow of coated lightweight aggregates increased by 10%, and also coating process reduced the water absorption of the aggregates up to 82%. The compressive strength increased by up to 21% for the coated aggregates. Scanning electron microscopy was also used to investigate the microstructure of the mortar‐aggregate interface. Microstructural images showed a uniform and dense interfacial zone of cementitious matrix‐aggregate for coated lightweight aggregates. Moreover, an improvement of 50–150 μm in the interfacial zone's thickness was seen for coated aggregates compared to uncoated aggregates.