The paper presents the VCCTL computer modeling of 28-day curing mechanisms of the type CEM I 42.5B Portland cement (Topki, Russia) within the temperature range from 0 to 99 оС. The water-cement ratio is 0.4. The VCCTL modeling results show the general hydration (hydrolysis) process of clinker phases, the amount and the composition of hydration products, pore space, ion composition of the aqueous solution, effective values of the elastic moduli (shear modulus, bulk modulus, Young’s modulus, and the Poisson ratio) depending on the curing time within the temperature ranging from 0 to 99 оС, after every 10 оС. It is shown that at 10 оС, CEM I 42.5B cement hydration is 52% and with the temperature increase up to 99 оС, it reaches 90% leaving the most of hydration to the first 50 hours. The temperature dependence of the heat transfer factor substantially correlates with the hydration degree. The temperature increase causes the growth in the hydration (hydrolysis) process of clinker minerals. During the first 50 hours, at a temperature higher than 60 оС, the amount of alite and aluminate decreases by an order of magnitude against the amount of belite and ferroaluminate that reduces by two times. During the subsequent temperature increases, the monotonous retardation of the dissolution rate is observed. The amount of the main hydration products (CSH, CH) in CEM I 42.5B increases and achieves 70% of the solid phase and the pore space. It is found that the effective values of the elastic moduli significantly grow during 400 hours, and then gradually decrease resulting in K = 16.79; G = 8.90; E = 22.69 МPа. The correlation is observed between the yield stress and Young’s modulus in the form of quadratic and cubic polynomials. Depending on the curing time and predicted values of Young’s modulus, the values of the yield stress obtained at Т = 20, 40, 50 and 70 оС are compared with the curing time, at the water-cement ratio of 0.4. The values of the yield stress are approximated using cubic polynomials. With a high degree of reliability (=0.97), the correlation between the yield stress and Young’s modulus is observed in the investigated temperature range. This correlation can serve as a basis for predicting the strength of Portland cement after 28-day curing.
|Publication||IOP Conference Series: Earth and Environmental Science|
|Position of speaker||Professor|
|Affiliation of speaker||Tomsk State University of Architecture and Building, Tomsk, Russia|