Using Isolated Temporal Analysis to Aid in the Assessment of Structural Element Quality for Additive Construction

Abstract

Additive construction (AC) is rapidly advancing as a viable method of construction. However, during layer deposition in concrete additive construction (concrete AC), deviations from the design can occur regarding tolerance, precision, and accuracy from layer to layer. This is primarily a result of the material's setting time and external factors such as ambient temperature and hose friction. Delayed placement of material can disrupt the interface strength, layer shape stability, and structural print stability during construction. Since the 3D printer systems used in AC processes are controlled by computers, it is possible to monitor and record the construction process to determine time gaps between layers and total construction, print, and elapsed times. This can be done by performing a time series analysis during the AC process. Isolating the components within the analysis that constitute the deseasonalized time can aid in determining certain aspects that can affect component irregularities. Using the autoregressive integrated moving average (ARIMA) method of time series forecasting, this analysis, alongside physical test results of material properties such as rheology, curing times, shape stability, and specimen strengths based on layer placement and time gaps, can provide a real-time assessment of construction quality. The work presented is on the development of a standard method for performing a time series analysis and the determination of specific time parameters completed over three different concrete AC demonstrations. The time series analysis disclosed that the optimal time for concrete printing in an outdoor environment would be during the early morning hours and late afternoon when the sun is not influencing the specific material composition. The results also indicated that after a 28-day curing time, the structural integrity of 3D-printed concrete decreased with variations in the layer print time of a single object, affecting the entire infrastructure.