Effect of Superplasticizer in Cement Type on Morphological Characteristics of Masonry Mortar

Abstract

Cement plays a crucial role in mortar composition, and its particles exhibit a strong tendency to flocculate when mixed with water. This flocculation necessitates the addition of substantial water to improve the workability of mortar or concrete. However, this extra water does not contribute to the hydration reaction, potentially weakening the mechanical properties of the mortar. The introduction of superplasticizers has addressed this issue by reducing the water demand. Nevertheless, a common practice in construction is to use a standard dosage of superplasticizers for the same type of cement, even when sourced from different cement factories, which may affect material performance. This study investigated the influence of varying superplasticizer dosages on Portland pozzolana cement from different Ethiopian cement factories, examining the morphological characteristics of masonry mortar. Specifically, it evaluated the impact on cracks, porosity, and surface structure across different curing ages, as well as assessed the mortar’s physical and mechanical properties. Mortar samples prepared using cement from three factories, labeled A, B, and C, with constant cement‐to‐sand ratios of 1:3 and water‐to‐cement ratios of 0.5. Superplasticizer added in varying amounts 0%, 0.6%, 0.8%, and 1%. The morphological analysis conducted using a 3D optical surface profiler microscope at 1, 7, 21, and 28 days. Besides these standard physical and mechanical tests also performed on all samples. The results demonstrated that addition of superplasticizers significantly influenced the surface morphology of mortar samples. Mortars A and B exhibited denser structures with superplasticizer dosages 0.8% and 1%, respectively, whereas mortar C displayed a denser structure in its control state (without superplasticizer). The flexural and compressive strength tests also revealed notable differences. Sample A2 (0.8%) from group A, sample B3 (1%) from group B, and sample C0 (0%) from group C achieved the highest strength within their respective groups at 28 days. The findings suggest that it is essential to evaluate the specific properties of cement before applying a standardized superplasticizer dosage, as variations in cement production can significantly influence the performance of the mortar.