A simple optimized foam generator and a study on peculiar aspects concerning foams and foamed concrete

This paper presents a study on peculiar aspects influencing foams and foamed concrete properties, starting from the foam generation up to the compressive strength of the lightweight and ultra-lightweight cementitious material. In particular, after a brief introduction on foam stability, this research work shows a simple and inexpensive foam generator used to produce the commonly used foams in concrete. The significant influence of the air pressure value, of nature and concentration of the foaming agents on density as well as the percentage drainages of the foams produced are therefore discussed. The results show that foams generated with the protein foaming agent have more suitable characteristics to produce foamed concrete, thanks to the significantly longer lifetime compared to foams produced with the synthetic foaming agent. The latter are characterized by very high drainage values even after a few minutes from their generation. Foams are then used to make lightweight (target dry density equal to 600 kg/m3 and 800 kg/m3) and ultra-lightweight (target dry density of 400 kg/m3) foamed concretes that show interesting results in terms of stability also when foams with high drainages are employed. The study provides explications of the differences between the compressive strength of lightweight foamed concrete obtained with foams generated using protein and synthetic foaming agents. Then, the significant influence of the increase in concentration of protein foaming agent on the compressive strength of ultra-lightweight foamed concretes is presented.