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    Effect of Water-Reducing Admixtures Having Hybrid Silicon Air-Entraining Surfactants on Some Properties of Concrete Mixtures
    (Asce-Amer Soc Civil Engineers, 2022) Emin, Ayvaz; Ozen, Suleyman; Mardani-Aghabaglou, Ali; Unlu, Ayda; Kapti, Tolga
    In order to improve the fresh properties and freeze-thaw resistance of cementitious systems, water-reducing and air-entraining admixtures are actively used in concrete mixtures. Generally, these mentioned admixtures are added to concrete mixtures as two separate admixtures. In this case, when the properties/compositions of one of the admixtures change, compatibility problems of admixtures may occur with each other or with the cement, and the fresh/hardened properties of the concrete may be adversely affected. In this study, a modified water-reducing admixture with both fluidity and air-entraining properties was produced. The utilization effect of high-range water-reducing admixtures (HRWR) having different ethylene oxide/propylene oxide (EO/PO)-based air-entraining surfactants (AES) on some properties of concrete mixtures was investigated. For this purpose, firstly, hybrid silicone AESs with a silicon content of 20%, 33%, and 38.5% were supplied. Then, HRWRs containing seven different AES were produced by using substitution and synthesis methods. In HRWRs produced by the substitution method, 3 and 5 wt. % of HRWR were substituted with EO/PO-based hybrid silicon AES. In the other method, EO/PO-based hybrid silicon air-entraining macromonomers were bonded to the HRWR at ratios of 1, 3, and 5 wt. % during its synthesis process. Replacing HRWR with hybrid silicone AESs increased admixture demand to provide the target slump value in concrete mixtures. Utilization of AESs containing 20% and 33% silicon in HRWR by the substitution method positively affected the permeability and compressive strength of concrete mixtures, while the rise of this ratio to 38.5% by using the synthesis method did not affect them significantly. The presence of surfactant with 20% silicon in 3% and 5% of the admixture and with 33% silicon in 5% of the admixture positively affected frost resistance of concrete mixtures. However, the use of surfactants with 33% silicon content in 3% of the admixture and 38.5% silicon in 1%, 3%, and 5% of the admixture showed a negative effect on the frost resistance of the mixtures.
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    Utilization of high-range water reducing admixture having air-entraining agents in cementitious systems
    (Elsevier, 2023) Sahin, Hatice Gizem; Mardani, Ali; Ozen, Suleyman; Emin, Ayvaz
    Utilization of admixtures with different action mechanisms has increased by combining them both physically and chemically. The effect of the use of modified water reducing admixture hav-ing air-entraining agents on the some fresh and hardened state properties of concrete mixtures was investigated in this study. It was determined that the utilization of air-entraining admixtures (AEA) increases the workability of fresh concrete due to the fact that it creates spherical-shaped air bubbles in matrix. However, there are contradictions about the effect of cementitious systems on rheological properties in the literature. Also, compatibility problems may occur when high range water-reducing admixtures (HRWRA) and AEA are used together in mixtures. It was re-ported that the use of HRWRA causes an increase in the spacing factor and the action perfor-mance of the AEA is adversely affected. However, it was understood that limited studies were car-ried out on increasing the compatibility of these admixtures in the literature. The methods that can be applied to prevent these incompatibilities were evaluated. First, the incompatibility be-tween them can be reduced by optimizing the order of adding the admixtures (HRWRA and AEA) to the mixture. Secondly, it was understood that the use of water-reducing admixtures modified with air-entraining properties in concrete mixtures can eliminate the stated incompatibilities.