The use of inorganic ferrous-ferric oxide nanoparticles to improve fresh and durability properties of foamed concrete

Enhanced fresh and hardened properties of foamed concrete modified with nano-silica

Nowadays, the application of nanotechnology has gained increased attention in the concrete technology field. Several applications of concrete require light weight; one such concrete used is foamed concrete (FC), which has more voids in the microstructure. In this study, nano-silica (NS) was utilized, which exhibits a pozzolanic nature, and it reacts with other pozzolanic compositions (like lime, alumina, etc.) to form hydrated compounds in concrete. Apart from these hydrated compounds, NS acts as a filler material and enhances properties of concrete such as the fresh and hardened properties. This research examines the fresh, hardened, and microstructural properties of FC blended with NS. The ratio of binder and filler used in this research is 1:1.5, with a water-to-binder ratio of 0.45 and a density of 880 kg/m3. A total of six different weight fractions of NS were added to FC mixes, namely 0%, 1%, 2%, 3%, 4%, and 5%. Properties assessed for FC blended with NS were the slump, bulk density, strength parameters (flexural, splitting tensile, and compressive strengths), morphological analysis, water absorption, and porosity. It was concluded from this study that the optimum NS utilized to improve the properties was 3%. Apart from this, the relationship between the mechanical properties and NS dosages was developed. The correlations between the compressive strength and other properties were analyzed, and relationships were developed based on the best statistical approach. This study helps academicians, researchers, and industrialists enhance the properties of FC blended with NS and their relationships to predict concrete properties from other properties.

Experimental Study on the Application of Recycled Concrete Waste Powder in Alkali-Activated Foamed Concrete

The alkali-activated cementitious material was prepared by partially replacing slag with recycled concrete powder (RCP). The influence of RCP substitution rates (10%, 20%, 30%, 40%, and 50% mass fraction) on the performance of alkali-activated slag-RCP-based (AASR) foamed concrete was studied. The fluidity, water absorption, softening coefficient, compressive strength, flexural strength, drying shrinkage, thermal conductivity, and frost resistance of AASR foamed concrete were studied. The results show that the fluidity and softening coefficient of AASR foamed concrete decreases with the increase in RCP content, and the fluidity range is 230-270 mm. Due to the porous structure of the RCP, the water absorption of AASR increases. With the increase in the curing age, the strength of AASR foamed concrete increases. The addition of RCP reduced the mechanical properties of AASR foamed concrete. Compared with the control group, the compressive strength of AASR50 decreased by 66.7% at 28 days, and the flexural strength decreased by 61.5%. However, the 28 d compressive strength of AASR foamed concrete under all RCP replacement rates still meets the standard value (0.6 MPa). The addition of RCP effectively reduces the thermal conductivity of the AASR foamed concrete, and when the RCP content is 50%, the thermal conductivity is lowest, 0.119 W/(m·K); the drying shrinkage of the AASR foamed concrete can be improved by adding RCP, and the drying shrinkage value is lowest when the RCP is 30%, which is 14.7% lower than that of the control group. The frost resistance of AASR foamed concrete decreases with the increase in the RCP content. When the recycled micropowder content is 20-50% and after 25 freeze-thaw cycles, AASR foamed concrete has reached freeze-thaw damage.