Investigation into the seamless construction for hundred-meter scale super-length raft structure based on magnesia expansive agent concrete

Abstract

This research introduces an innovative construction method based on magnesia expansive agent concrete for the seamless construction of hundred-meter scale super-length raft structures, corroborated by the on-site test. The basic principle of this construction method is to use the pre compression stress generated by magnesia expansive agent to offset temperature and shrinkage stress. A temperature-strain monitoring system was employed to gather data, affirming the technique’s applicability and safety. Through the examination of temperature and strain dispersion trends in super-length raft structure, recommendations for the configuration of temperature-strain sensors have been put forth. Through the scrutiny of the temporal evolution pattern of temperature, the specific temporal and spatial coordinates that warrant particular vigilance during the surveillance of the raft’s inner-surface temperature difference were identified. Upon evaluating the correlation between strain dispersion and strain-temperature differential in the raft’s thickness dimension, a novel temperature control index (the bottom-surface temperature difference) was introduced. The threshold for this metric was established at 30°C, derived from empirical test outcomes conducted on-site. Furthermore, the critical regions for monitoring the bottom-surface temperature difference were specified.

Numerical Simulation and Calculation Method Study on Seamless Construction of Super-Length Raft Structures Based on Novel Magnesium Oxide Expansive Strengthening Band Method

“…This section aims to rigorously validate the predictive capability of the established FEM for the mechanical and thermodynamic performance of super-length raft structures with ESBs through systematic comparative analyses. Specifically, this section presents in detail the outcomes from finite element analysis (FEA), including the principle of temperature distribution, principle of strain distribution, temperature-time characteristics, and strain-time characteristics, juxtaposing them directly with data obtained from on-site tests [34]. The validation process encompassed not only quantitative comparisons of results, such as the congruence between modeled temperatures and strains with actual measurements, but also qualitative assessments of characteristic features to ensure that the simulation accurately replicates physical phenomena observed in the on-site tests.…”

“…According to the literature [34], during the thermal accumulation phase, the temperature of the raft continuously rose, reaching its peak at 48 h post-pouring. The principle of temperature distribution across the surface, center, and bottom of the raft, as compared between FEA and experimental data, are depicted in Figure 3.…”

“…The standard region of the raft was constructed with C35 concrete, and the ESB employed C40 concrete; detailed mix proportions are outlined in Reference [34]. The testing procedures for assessing the physical and mechanical properties of the concrete, not detailed in [34], adhered to the requirements outlined in the 'Standard for test methods of concrete physical and mechanical properties' (GB/T50081-2019) [35], ensuring a rigorous evaluation of the materials' performance. According to the 'Test code for hydraulic concrete' SL/T 352-2020 [36], the thermodynamic properties of both C35 and C40 concrete were calculated separately, as presented in Table 1.…”