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Coral aggregate has been widely used for island construction because of its local availability. However, the addition of coral aggregate exaggerates the brittle nature of cement-based materials under dynamic loading. In this study, polyvinyl alcohol (PVA) fiber was used to improve dynamic mechanical behavior of seawater coral mortars (SCMs). The ef...
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... fiber surface was smooth, and the fibers were held together tightly. Table 4 lists the physical properties of the PVA fiber. To improve the workability of the freshly prepared mortar, a polycarboxylate-based high-range water reducing admixture (HRWRA) was employed in this study, consistent with the requirements of the JG/T223 Standard [25]. ...Context 2
... fiber surface was smooth, and the fibers were held together tightly. Table 4 lists the physical properties of the PVA fiber. To improve the workability of the freshly prepared mortar, a polycarboxylate-based high-range water reducing admixture (HRWRA) was employed in this study, consistent with the requirements of the JG/T223 Standard [25]. ...Citations
... However, in the process of island construction, transportation costs and construction durations will undoubtedly be increased if all building materials (especially concrete) need to be transported by land [4][5][6]. In addition, due to the special environment of islands, island buildings and constructions inevitably face the threat of dynamic loading, resulting from phenomena such as earthquakes and explosions [7,8]. Therefore, methods for producing and processing seawater coral aggregate concrete (SCAC) enable to meet the requirements of island and reef engineering construction using local materials in order to reduce economic costs and shorten construction periods while satisfying the needs of island and reef engineering construction projects is a key issue in island and reef construction. ...
... Studies have shown that the mechanical properties of concrete are closely related to the composition and structure of concrete [13][14][15][16]. Some scholars have explored ways of improving the strength of SCAC by optimizing the mix ratio [8,17,18], while others have attempted to improve the performance of SCAC by adding fibers to SCAC. Some scholars have attempted the addition of plant fibers (such as sisal fibers) to SCAC to improve its performance [7,19,20]. ...
The development of island construction concrete can serve as a basis for the development and utilization of island resources. Complying with the principle of using local materials to configure seawater coral aggregate concrete (SCAC) that is able to meet the requirements of island and reef engineering construction could effectively shorten the construction period and cost of island and reef engineering construction. In this paper, quasi-static mechanical experiments and dynamic mechanical experiments were carried out on SCAC with different limestone powder contents. High-speed photography technology and Digital Image Correlation (DIC) were used to monitor the dynamic failure process and strain field of SCAC, and the influence of limestone powder content on the dynamic and static mechanical properties of SCAC was investigated. The results showed that, when the limestone powder content was 20% and 16%, the quasi-static compressive strength and quasi-static tensile strength exhibited the best improvement. Additionally, with increasing limestone powder content, the dynamic tensile strength of SCAC first showed and increasing trend and then a decreasing trend, reaching its maximum value when the limestone powder content was 16%. Moreover, the maximum strain value of SCAC with the same limestone powder content increased with increasing strain rate grade, showing an obvious effect on strain rate.
... Wu et al. (2021c) found that the DIF of coral aggregate concrete increases with the growth of strain rate. Long et al. (2020) indicated that the addition of polyvinyl alcohol (PVA) fiber can improve the dynamic mechanical behavior of seawater coral mortars, which is manifested in the enhancement of energy dissipation under dynamic loading. Similarly, Yue et al. (2020) found that the tensile strength of coral aggregate concrete is improved after adding sisal fiber, but it has no obvious effect on the tensile strength DIF. ...
Coral sand is one kind of the important building materials in coral reef engineering practice. The use of cement as a stabilizing agent can significantly improve the mechanical properties of coral sands and is widely applied in the subbase engineering construction in coral reef islands. Cement-stabilized coral sand structures may contain high contents of fine coral particles and salinity because of the high crushability of coral sands and the existence of seawater surrounding them. In this study, the effects of coral sand powders and seawater salinity on the dynamic mechanical properties of cemented coral sand (CCS) were investigated through the split Hopkinson pressure bar (SHPB) tests and Scanning Electron Microscope (SEM) analysis. It was found that the strength (i.e., the peak stress) of CCS specimens increased firstly and then decreased with the increase of powder content. The specimens reached the maximum peak stress when 3% powder content was included. The initial improvement of CCS strength was attributed to the pore-filling effect of coral powders, namely, the micro pores of the CCS specimens could be more effectively filled with higher percentages of coral powders being used in the experiments. However, excessive coral powders resulted in the reduction of specimen strength because these powders could easily be cemented into agglomerates by absorbing water from the specimens. These agglomerates could reduce the cementation strength between the coarse coral particles and the cement. Meanwhile, the peak stress of CCS specimens was found to be negatively correlated with the average strain rate and the ultimate strain. The degree of specimen fracture was found to be correlated with the amount of specific energy absorption during the tests. Furthermore, the “sulfate attack” caused by the inclusion of salinity of water had different influences on the CCS specimens with different coral powder contents. The ettringite and gypsum produced in “sulfate attack” could fill the pores and lead to cracking of the specimens, significantly affecting the specimen strength.
... It can be clearly seen from Fig. 3 that similar trends in the storage modulus can be observed at frequencies of 0.5, 1.0, 1.5, and 2.0 Hz, in which the storage modulus was reduced with increasing the temperature. However, it should be noted that there was a sharp decrease occurred after it reached to 35 • C. The storage modulus is commonly used to indicate the stiffness and brittleness of the material, in which, the higher storage modulus generally suggested smaller deformation under a given load [45]. Therefore, the significant change of storage modulus indicated that the temperature adaptivity occurred around 35-40 • C, which proved the concept of TAM40. ...
The ease to be ruptured during mixing due to the brittleness of microcapsule shell limits the self-healing performance of microcapsules in concrete. In this study, a novel type of microcapsule with temperature-adaptive property (TAM) under different mixing temperatures was proposed to tackle this issue. The effect of TAM content and mixing temperature in self-healing cementitious materials was investigated. Based upon the confirmation of temperature adaptivity of microcapsule shell by dynamic mechanical analysis, the early age properties, including minislump, setting time and hydration heat, and the hardened properties of compressive strength and shrinkage, were determined. Moreover, the self-healing performance, in terms of strength healing and recovery rate, as well as the pore structures, of TAM in cementitious material was investigated. The results showed that the addition of TAM decreased workability and slightly extended the setting and hydration of cement, while the elevation of mixing temperature reduced workability and accelerated the setting and hydration of cement. Moreover, the addition of TAM and low mixing temperature reduced the compressive strength and shrinkage of hardened paste. Compared to the low mixing temperature, the self-healing performance in terms of strength and chloride migration was improved at high mixing temperature. The results proved the design concept of temperature adaptive microcapsules.
