Study On Hydration Process Of Portland-Cement-Based Cementitious Material System Based On Non-Assumptive Projection Pursuit Regression Modeling

Exploring the laws of heat release from the hydration of cementitious materials and studying the hydration process of cementitious materials can help to prevent and control common temperature cracking problems in concrete.The seven-day hydration heat of ordinary Portland cement,high sulfate-resistant Portland cement,medium heat Portland cement,and low heat Portland cement with different fly ash and slag admixtures were measured.The applicability of traditional hydration heat model and hydration kinetics model to Portland-cement-based cementitious material system was discussed.Finally,the internal structure and characteristics of the high-dimensional observations were processed and analysed using the non-assumptive projection pursuit regression（NA-PPR）modeling method,which belongs to the exploratory data analysis（EDA）method.The NA-PPR model of heat hydration and the NA-PPR model of hydration kinetics for Portland-cement-based cementitious material system were built.Specifically result as follows:（1）A hydration heat model for the Portland-cement-based cementitious material system was developed based on the NA-PPR method,which used a numerical function to describe the projected ridge function and taked the“accuracy consistency criterion”and three-layer-grouping iterative to optimising parameters.The established NA-PPR hydration heat model is visual and intuitive,and can predict the hydration heat from 1d to 7d of the Portland-cement-based cementitious material system with different fly ash and slag admixture,with the qualification rate（75.2%and 73.6%）and mean absolute error(8.3 J·g^-1and 8.9 J·g^-1)of the modeling samples and testing samples,respectively.Comparing the classical hydration heat model and the BP neural network,it can be seen that the NA-PPR hydration heat model has good stability and versatility,and avoided the uncertainty of calculation results caused by artificial assumption and subjectively parameter selection in traditional hydration heat models.It is shown that NA-PPR hydration heat model can explore the intrinsic structural characteristics of the high-dimensional data on the hydration heat of Portland-cement-based cementitious material system.（2）A hydration kinetic model of the Portland-cement-based cementitious material systems was established by combining the NA-PPR hydration heat model with the hydration rate equation,the NA-PPR model avoided the large errors problems in the calculated hydration rate for the traditional hydration kinetic model,which caused by the artificial assumption of the maximum range of hydration and the division of hydration into three mechanistically different stages.The proposed NA-PPR hydration kinetic model can objectively and accurately describe the hydration rate from 1h to 48h of Portland-cement-based cementitious material systems under different fly ash admixture conditions by the content of four mineral components of cement,fly ash content,cement fineness and hydration age,and the simulated hydration rate curves basically match with the actual rate curves.It is shown that the NA-PPR hydration kinetic model can objectively and accurately describe the hydration process of Portland-cement-based cementitious material system with mineral admixtures.