Crossover Effect in Cement-Based Materials: A Review

Yousuf, Sumra; Shafigh, Payam; Ibrahim, Zainah; Hashim, Huzaifa; Panjehpour, Mohammad

doi:10.3390/app9142776

Cited by 19 publications

(5 citation statements)

References 50 publications

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“…This trend is generally consistent with the observations made in [15,16], where accelerated hydration, denser calcium-silicate-hydrate (C-S-H) structures, and reduced porosity were reported at increased temperatures up to 70°C. These factors contribute to the faster development of strength in concrete [16].…”

Section: Resultssupporting

confidence: 91%

Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance

Straßer,

Kränkel,

Gehlen

2023

ce papers

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This research aims to integrate the Wire Arc Additive Manufacturing (WAAM) process into the Selective Paste Intrusion (SPI) process to enable the production of reinforced concrete elements with complex geometries. However, the high temperatures generated during the steel melting process in WAAM can locally lead to a full stop of hydration which consequently is linked to a decrease of the mechanical properties of the concrete in the bonding zone around the reinforcing bar. This study aims to determine the maximum allowable temperature at which concrete retains sufficient hardening conditions which allows strength development when combining SPI with WAAM. In practical application, this temperature limit can directly be affected by e.g. the protruding length of the WAAM‐reinforcing bar above the SPI particle bed or external cooling strategies. As continuation of previous research, this study establishes a link between actual and targeted temperatures in the steel bar to allow the combination of WAAM and SPI processes. Temperature limits without compromising mechanical performance are investigated, and the need for and extent of additional cooling measures are evaluated. The results show that temperatures of the concrete in the fresh state can reach up to 70°C without weakening its mechanical performance.

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Section: Resultssupporting

confidence: 91%

Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance

Straßer,

Kränkel,

Gehlen

2023

ce papers

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“…This behavior is due to the competing effects of acceleration of hydration of the non-hydrated cement and degradation due to microcracking [49]. This hydration results from the passage of water vapor released by the pores originating steam condition under the effect of the so-called internal autoclaving that occurs from 160 • C to 220 • C in cement-based materials [58,59]. After 200 • C, decomposition of C-S-H gel and the sulfoaluminate phase cause cracks with significant effect on the compressive strength [60].…”

Section: Young's Modulus Dynamic Shear Modulus Poisson Ratio and Compressive Strengthmentioning

confidence: 99%

Influence of Exposure to Elevated Temperatures on the Physical and Mechanical Properties of Cementitious Thermal Mortars

et al. 2020

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Thermal mortars incorporating insulating aggregates are a possible solution to ensure good thermal performance and thermal comfort in buildings due to their low thermal conductivity coefficient. Under some circumstances, namely for particular in-service conditions in industrial applications and/or accidental actions (such as fire), it is important to quantify the retention of their properties after exposure to elevated temperatures, however this information is not yet available in the literature. This study aims to characterize the physical and mechanical behavior of thermal mortars incorporating expanded clay, granulated expanded cork and silica aerogel as aggregates after exposure to elevated temperatures. To this end, five types of mortars were produced in laboratory conditions—three thermal mortars, one reference sand mortar and one sand mortar with admixtures—and then exposed to different elevated temperatures (from 20 °C to 250 °C) in a thermal chamber. After thermal exposure, the following properties were assessed: bulk density; ultrasonic pulse velocity; dynamic elasticity modulus; dynamic shear modulus; Poisson coefficient; compressive strength; and thermal conductivity. The results obtained show that residual properties present a very high dependence on the reactions that take place in the cement paste when the mortars are exposed to elevated temperatures. After such exposure, all mortars with thermal insulating aggregates were able to maintain their insulating characteristics, but experienced internal damage and degradation of their mechanical properties. Results obtained also showed that insulating aggregates allowed to produce mortars with higher aggregate-cement paste compatibility at elevated temperatures compared to conventional mortars, resulting in less micro-cracking of the mortar, and leading to lower reductions in thermal conductivity with increasing temperature.

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“…This could have created a thermal effect that led to the formation of a substantial amount of hydration products coating the cement particles, which impeded further hydration of the cement [57]. Another possibility is that exposure to elevated temperatures led to an uneven distribution of hydration products, which were under development at this stage [60]. This phenomenon, termed the crossover effect, occurs when concrete or cement-based materials are subjected to a higher initial curing temperature, which speeds up hydration but causes uneven distribution of the hydration products.…”

Section: Effect Of Microwave-assisted Curing On Ucsmentioning

confidence: 99%

Experimental Development of an Innovative Approach to Enhance the Strength of Early Age Cemented Paste Backfill: A Preliminary Investigation of Microwave-Assisted Curing

Hefni

2023

Minerals

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In underground mining, the application of mine backfill has evolved into a standard practice. Mine backfill typically consists of tailings, water, and hydraulic binders. However, the high cost of binders has prompted scholars to research alternatives to reduce this cost while maintaining or even improving the properties of the backfill. One potential alternative is leveraging microwave irradiation. In this study, an innovative approach was developed to increase the unconfined compressive strength (UCS) of early age cemented paste backfill (CPB). Microwave treatment was applied to CPB samples at various curing ages for varying durations. The UCS and ultrasonic pulse velocities were measured and analyzed in an experiment with a full factorial design. Moreover, the microstructural properties of the CPB were investigated using mercury intrusion porosimetry. The results indicate a significant potential to increase the UCS of CPB by up to 25% when microwave-treating samples for 8 min after 7 days of curing. This approach could shorten mining cycle times and improve productivity, presenting a promising method to enhance CPB strength.

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Crossover Effect in Cement-Based Materials: A Review

Cited by 19 publications

References 50 publications

Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance

Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance

Influence of Exposure to Elevated Temperatures on the Physical and Mechanical Properties of Cementitious Thermal Mortars

Experimental Development of an Innovative Approach to Enhance the Strength of Early Age Cemented Paste Backfill: A Preliminary Investigation of Microwave-Assisted Curing

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