Investigating the performance of cementitious materials on mechanical properties and durability against the combined effects of freeze-thaw cycles and de-icing salt in early utilization of concrete pavements

One of the main objectives of infrastructure managers is the timely and rapid operation of airports and freeways. A goal that is challenging when utilizing concrete pavements, due to their different behavior during the initial stages of implementation. This research aims to improve the mechanical characteristics of concrete pavements and increase their durability against the combined effects of the freeze-thaw cycle and surface desalination, especially during early ages. This paper examines the use of cementitious material in combination with hydrated lime, metakaolin, and zeolite to remove the hurdles to the early operability of concrete pavements. To this end, micro-structural studies have been performed using XRD and SEM analysis and comparisons in two states of water processing and exposure to freeze-thaw cycle. During which replacing cement with zeolite and metakaolin in calcareous concrete resulted in reduced porosity and homogeneous density with the formation of CSH in the concrete structure.  Accordingly, improvements in the mechanical properties and durability of concrete pavements against the combined effects of freeze-thaw cycle and surface desalination were studied and analyzed in four mixtures of Control Concrete (CC), 15% lime (CL), 15% lime, and 15% Metakaolin (CLM) and 15% lime and 15% Zeolite (CLZ). It was noted that at age of 7 days the CLM, CL, and CLZ samples showed an increase of 20%, 32%, and 48% respectively compared to the CC sample. This increase continued throughout the study. During the freeze-thaw test and after 55 cycles the CLM and CLZ samples always exhibited lower degradation and showed a weight loss of 48.7% and 75.2% less than the CC sample. In addition, as per the results of the capillary absorption test the CLM and CLZ mixtures had at lower ages had less permeability than the CC mixture and this behavior continued with better performance at older ages.    Also, the results of flexural strength indicate the positive effect of additives in all samples over time, and at 28 days, the CL, CLM, and CLZ samples increased flexural strength by 39%, 42%, and 57% respectively in comparison to the CC sample. The positive effect of hydrated lime due to its high paste property in increasing the flexural strength of mixtures containing metakaolin and zeolite is quite evident and has increased the mechanical properties at all ages of the samples, but has weakened the durability performance compared to the control sample. This issue has been addressed in composite mixtures containing lime with metakaolin or zeolite, and the results of durability tests indicate a significant improvement in both pozzolans, especially in the zeolite. It can therefore be concluded that with improving mechanical characteristics and durability of CLM and CLZ mixtures, utilizing metakaolin and zeolite in concrete containing hydrated lime is a suitable solution to eliminate the challenges of early usage in concrete pavements.