Prediction of Plastic Shrinkage Cracking of Supplementary Cementitious Material-Modified Shotcrete Using Rheological and Mechanical Indicators

Abstract

Plastic shrinkage cracking is a complex and multifaceted process that occurs in the period between placement and the final setting. During this period, the mixture is viscoplastic in nature and therefore possesses rheological properties. The investigation of the relationship between rheological behavior and its propensity to undergo cracking during the plastic phase presents an intriguing subject of study. However, many factors influence plastic cracking, and the corresponding interaction of its effects is complex in nature. This study aimed to evaluate the impact of rheological and physicomechanical properties on the occurrence of plastic cracking in high-performance shotcrete containing various supplementary cementitious materials. To achieve this, plastic cracking was evaluated employing the ASTM C 1579 standard and a smart crack viewer FCV-30, and the rheological parameters were controlled using an ICAR rheometer. In addition, a study was conducted to assess the strength development and fresh properties. Further, a relationship was established via statistical evaluation, and the best predicting models were selected. According to the study results, it can be concluded that high-yield stress and low plastic viscosity for colloidal silica mixtures are indicators of plastic cracking resistance owing to improved fresh microstructure and accelerated hydration reaction. However, earlier strength development and the presence of a water-reducing admixture allowed mixtures containing silica fume to achieve crack reduction. A higher indicator of yield stress is an indicator of the capillary pressure development of these mixtures. In addition, a series containing ultrafine fly ash (having high flow resistance and torque viscosity) exhibited a risk of early capillary pressure build-up and a decrease in strength characteristics, which could be stabilized with the addition of colloidal silica. Consequently, the mixture containing both silica fume and colloidal silica exhibited the best performance. Thus, the results indicated that rheological characteristics, compressive strength, and water-reducer content can be used to control the plastic shrinkage cracking of shotcrete.

High-Performance Materials Improve the Early Shrinkage, Early Cracking, Strength, Impermeability, and Microstructure of Manufactured Sand Concrete

“…The reduction and optimization of water absorption can effectively improve the cracking and shrinkage properties of concrete. Yun et al [23] evaluated the effects of rheological and physicomechanical properties on the plastic cracking of high-performance shotcrete concrete containing various supplementary cementitious materials. Furthermore, some other studies [24][25][26][27][28][29][30][31][32] also show that in addition to traditional measures for reducing the shrinkage and cracking of concrete from the raw materials, such as coarse aggregates, fine aggregates, and water reducers [24,25], new material methods, such as adding FS [26][27][28] or a high-efficiency SRA [29,30] and fiber toughening [31,32], and internal curing methods, such as SAP [21,25], can also be used to reduce the shrinkage and cracking of concrete.…”