Air incorporation in ready mix mortars: influence of admixtures, aggregates and mixing time

Abstract Air incorporation is a complex issue that affects the properties of both fresh and hardened mortars. Ready-mix mortar is a mix that contains a high content of entrained air, and has an applicability of up to three days due to the use of air entraining admixtures (AEA) and hydration stabilising admixtures (HSA). This study evaluated the influence of AEA and HSA, aggregate type and mixing time on air entrainment in ready-mix mortars. In the investigation, 36 mortar mixtures were prepared with different mixing times (150, 210, 270 and 330 s). Two sand particle sizes were studied, using different contents of HSA (0%, 0.6% and 0.9%) and AEA (0% to 0.5%), a standard proportion for rendering mortars (1:6.5) and a water/binder ratio of 1.0. The results indicated air entrainment stabilisation with a mixing time of 270 seconds and an AIA content between 0.3% and 0.4%, whereas HSA did not contribute significantly to air entrainment. Mixing time influenced air entrained in mortars only with an AEA content 0.3% or higher, while aggregate particle size only influenced mortars without AEA or with AEA up to 0.2%.