Features of setting and strength gain of the foam concrete massif

The paper presents a study of the regularities of the processes occurring in the matrix and aerated concrete mass at the initial time after laying and later, during the strength gain. The colloidal properties that appear in the foam concrete mix begin at the stage of mixing the components containing binder and aggregate particles, and are activated by the mixer blades. In this case, the mixture is transformed by mass transfer of the matrix material onto the foam grid and a new spatial reorientation of the bubbles under conditions of physical and mechanical effects on the thin-film structure of the foam. In technology, it should be taken into account that the processes occurring in the foam concrete mixture can be attributed to two opposite actions occurring simultaneously. First, in a freshly laid foam concrete mixture, as in any thermodynamically unstable system, sedimentation and coalescence of air pores begins, which is especially manifested at forcedly high water-solid ratios. This can lead, if the technology is not followed, to complete stratification of the mixture. Secondly, in the cement slurry, the setting and further formation of the cement stone occurs. A necessary technological condition for product quality is compliance with the optimal water-solid ratio of the mixture and ensuring the beginning of the setting of the foam concrete mass before its stratification. It was also experimentally determined that an increase in the hardening duration of foamcement systems for more than 28 days is impractical, since it was revealed that an increase in the strength of foam concrete is similar to the same process in structural concrete. It is quite possible to achieve the strength required for foam concrete according to GOST 25485-89 within 28 days and even earlier due to the high technological discipline and the use of modern plasticizing additives.