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Creep and shrinkage estimation for low-heat concrete mix used in the 2nd Avenue network arch bridge
Published in Joan-Ramon Casas, Dan M. Frangopol, Jose Turmo, Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 2022
K. Basnayake, U.B. Attanayake, M. LaViolette, M. Chynoweth
As shown in Table 1, 67% of the cement content is replaced with supplementary cementitious materials (SCMs). SCMs, such as fly ash and GGBFS, have been extensively used in the production of high strength concrete to improve fresh and hardened concrete properties. Limited studies have been conducted to evaluate the properties of concrete blended with slag and class F fly ash (Sakthivel Et al. 2019). The primary reason for using slag and class F fly ash is the lower heat of hydration that minimizes the cracking potential in mass concrete (Kosmatka and Wilson 2011, Basnayake Et al. 2020). The presence of high cementitious material content in concrete mixes with low w/cm ratios affects workability. The use of a high-range water reducer improves the concrete workability of such mixes, resulting in a flowable and a self-consolidating concrete. The optimized combination of high-range water reducers and other admixtures, such as water reducers or retarders, helps to develop strength and control setting times and workability at a relatively lower cost (ACI 2010). The air entraining admixtures are used to enhance concrete durability against freeze-thaw conditions and deicers. Sometimes, air entraining admixtures are used to control workability as well. Shrinkage reducing admixtures (SRAs) are used to reduce concrete shrinkage (Lopez Et al. 2013, Kioumarsi Et al. 2020).
Water reducing/retarding admixtures
Published in A. M. Paillère, Application of Admixtures in Concrete, 1994
When water reducers are used, then heat of hydration and temperature rise of concretes may be higher at early ages. When the water reducer is used to reduce the mixing water of concrete for a given workability, without modifying the mix proportions.
Recommendation for concrete mix design to prevent bleed channels on diaphragm walls
Published in European Journal of Environmental and Civil Engineering, 2022
Chafika Djelal, Yannick Vanhove, Amin Azzi, Olivier Madec
The BF1 and BF3 were designed using Polycarboxylate ethers as a water reducing admixture (WR) that they can give maximum water reduction and early strength development (Table 7). To obtain the same water reduction as that for mixes without fly ash, a polycarboxylate ethers high range water reducing admixture (HRWR) was added in the BF1 mixture. This HRWR improves the water reduction effect and the workability due to its steric hindrance. The BF2 mixture was formulated using a modified phosphonate HRWR to increase concrete workability with a reducing of the water content without compromising the setting time. This product allows having a very long preservation of workability. A lignosulfonate water reducer admixture complements the polycarboxylate ether-based plasticizer for the mixture BF3. A polyacrylate with graft polyether chains designed to disperse by steric hindrance was retained in the mixture BF4. The use of a CEM II/A L 42.5R CP2 in this formulation, to obtain a rapid setting of the concrete to accelerate onsite operations, required a set retarder to maintain the concrete workability during the casting process.
Durability of wet lay-up FRP bonded to concrete with nanomodified epoxy adhesives
Published in The Journal of Adhesion, 2020
Syed Ahnaf Morshed, Tyler J. Young, William M. Chirdon, Qian Zhang, Jovan Tatar
Concrete used to prepare beam specimens had a target compressive design strength of 69 MPa (10,000 psi). High strength concrete was chosen to force the interfacial failure along the FRP-concrete adhesive joint, instead of a cohesive failure within the concrete substrate. To achieve high compressive strength, a low water to cementitious material ratio (w/cm) of 0.353 was maintained. The concrete mixture was composed of: river sand, coarse aggregate corresponding to ASTM gradation curve #89, Portland Cement Type I/II and admixtures – air entrainer (Darex AEA), plasticizer and water reducer (Adva Cast 600 and WRDA 60). Coarse aggregate moisture content was determined prior to mixing the concrete to adjust the batch quantities. The moisture content of the coarse aggregate was found to be 8.60%. No pozzolans were included in the concrete mix. Detailed mix proportions can be found elsewhere.[47] Average 28-day compressive strength of five (5) concrete cylinders was 69 ± 1.6 MPa .
Influence of waste glass aggregates on the rheological properties of self-consolidated concrete
Published in Australian Journal of Civil Engineering, 2020
Ayan Saha, Md. Habibur Rahman Sobuz, Md. Ikramul Hoque, Rashid Mujahid
The river sand obtained from local district Kustia, Bangladesh with a particle size of 4.75 mm Maximum conforming to the TS 706 EN 12620+ A1 (2009) was used as fine aggregate in this study. The physical properties of coarse and fine aggregates obtained from the various experimental studies are listed in Table 2 according to ASTM C127 (2015). The grading curve of coarse and fine aggregates is illustrated in Figure 2. An admixture with high range water reducer (HRWR) or superplasticizer (SP) was used for all concrete batches to expand the workability of fresh concrete. It was collected from Dhaka, Bangladesh. Fresh potable water free from organic matter and oil was used in mixing the concrete. Potable water conforming to the drinking standard was used for mixing the concrete batches. The pH value of the water was 7.35.