Evaluation of Suitability of Carboxymethyl Cellulose in Performance Improvement of Sodium Lauryl Sulfate Foam and Compressive Strength of Foam Concrete

Abstract

Currently, foam concrete is commonly used for various construction applications such as partitions, filling grades, road embankment infills, and sound and heat insulation. It is to be noted that the foam production parameters have significant influence on the cellular structure of foam concrete, which governs the material properties of concrete. Hence, in an attempt to improve the foam quality, the present work focuses on evaluation of the suitability of viscosity enhancing agent carboxymethyl cellulose (CMC) in performance improvement of foam produced with surfactant sodium lauryl sulfate (SLS) for use in foam concrete production. Firstly, the influence of the addition of CMC on behavior of foam produced with surfactant SLS was studied by evaluating essential characteristics such as foam density, foam stability, and viscosity of surfactant solution. As a next step, the microstructure of foam and its behavior in cement slurry and mortar at the optimized concentrations of SLS and CMC were studied. Experimental studies revealed that the addition of 0.2 % CMC to 2.5 % SLS surfactant solution resulted in a 134 % increase in viscosity of surfactant solution, which eventually resulted in tremendous improvement in foam quality in terms of 34 % reduction in foam drainage (at the 5th minute after foam generation) and 22 % reduction in larger size foam bubbles (D90). Furthermore, as the air void microstructure of foam concrete is dependent on the foam bubble sizes, the reduction in foam bubble sizes resulted in 20 % enhancement in compressive strength of foam concrete. The addition of CMC is also found to affect the workability of foam concrete mixes, which is evident from the reduction in flow spread and the increase in flow time. Also, as the foam has retarding properties, the increase in foam content is found to increase the demolding time requirement of foam concrete specimens.

The Stabilizing Effect of Carboxymethyl Cellulose on Foamed Concrete

“…The reduction of the average-size bubbles is due to the addition of CMC to the foaming solution, which improves the solution viscosity [ 13 ], so improving the strength of the liquid film [ 23 ], further inhibiting the combination and rupture of bubbles, effectively alleviating the generation speed of large bubbles, and giving foam a specific stability.…”

“…CMC belongs to anionic cellulose ethers, cellulose-like substances with carboxymethyl substituents that are easily dispersed in water to form transparent colloidal solutions and have a high thickening efficiency due to the abundance of hydroxyl groups as well as hydrophobic chain segments [ 12 ]. Acting in foam concrete, they can enhance the denseness of the foam surface layer, improve the ability of bubbles to resist rupture, and eliminate pore connectivity, rupture, and escape so that bubbles can exist stably in the cement slurry for a long time [ 13 ].…”

“…Merachtsaki and Domna [ 18 ], who studied the essential characteristics of foam and surfactant through the experimental system design based on the response surface method, found that the choice of surfactant and CMC concentration has a significant impact on the foam characteristics of foam concrete and then affects the pore-size distribution of foam concrete. Research by Sahu and Sritam Swapnadarshi [ 13 ] shows that adding 0.2% CMC to 2.5% sodium sulfate solution can effectively improve foam quality, and foam discharge and large-size foam can be significantly reduced. At the same time, the compressive strength of foam concrete increased by 20%.…”