Effect of Cement/Sand Ratio on Properties of Lightweight Foamed Concrete D900

Lightweight foamed concrete (LFC) is increasingly being applied in construction projects in Vietnam due to its low density, good sound and thermal insulation properties, and ease of fabrication into prefabricated elements. D900 LFC is a type of concrete with a density ranging from 850 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$950 \text{kg} / \mathrm{m}^{3}$</tex>, suitable for the construction of lightweight partition walls and floor slabs in building projects. This paper presents a study on the influence of the cement/fine sand ratio (C/S) on the properties of D900 LFC. The research was conducted with four different mix ratios of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C} / \mathrm{S}$</tex> (3/1, 2.5/1, 2/1, and 1/1). LFC mixtures were prepared with a water/cement (W/C) ratio of 0.32, and experiments were carried out to evaluate flowability, compressive strength, ultrasonic pulse velocity (UPV), water absorption, and electrical resistivity (ESR) of the foam concrete mixtures. The research results show that the mix with a C/S ratio of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.5 / 1$</tex> is optimal concerning compressive strength, ultrasonic pulse velocity, and water absorption. As the C/S ratio increases, both flowability and ESR values of the LFC mixtures increase at various ages. D900 LFC with a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C} / \mathrm{S}$</tex> ratio of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.5 / 1$</tex> meets the compressive strength requirement of grade B3.5 according to the standard TCVN 9029:2017, while the other C/S ratios achieve compressive strength of grade B2.5.