Experimental and numerical modeling of creep in different types of concrete

Creep in concrete, play a critical role in estimating losses in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. The present study aims at investigating the creep under various environmental conditions in different types of concrete made with different ingredients using an experimental and numerical approach. Seven different concrete mixes have been made for this purpose and among the seven mixes, three mixes are self compacted concrete mixes (35 MPa, 55 MPa and 70 MPa), a high volume fly ash concrete mix (45 MPa), two mixes of normally vibrated ordinary Portland cement (OPC) concrete mixes (35 MPa and 45 MPa) and a heavy density concrete (25 MPa). Studies have been carried out at temperature of 25 °C and two relative humidity (RH) conditions (RH of 60% and 70%). An analytical model has been developed to simulate the drying phenomena in concrete based on a poromechanics approach. The hydration effects in blended cements (containing mineral admixture) is considered while developing the model. The proposed model is capable of predicting the degree of hydration, temperature and relative humidity (RH) over the continuum that required for estimating the creep strain. Micro prestress solidification (MPS) is used to estimate the creep strain. It is found that the proposed model is able to predict the drying phenomena and creep strain in various concretes, and which is in good agreement with the corresponding experimental results. It is found that heavy density concrete shows a higher creep strain than the other concretes. This may be due to the lower porosity of hematite aggregate. Further adding fly ash as a mineral admixture to concrete mix reduces the creep. Creep in a reinforced concrete (RCC) beam tested under sustained loading and reported in the literature is simulated using the present model and it is seen that the model predictions are in good agreement with the test data.