Abstract
Concrete is one of the most popular construction materials in the world. Chemical admixtures are ingredients added to concrete to enhance its properties. However, most chemical admixtures on the market today are expensive, thereby making them out of reach for small consumers of concrete. In Africa, use of chemical admixtures is rare despite the harsh weather conditions. In the current study, Gum from Acacia karroo (GAK) was used as a water-reducing admixture in concrete. A slump test, density and compressive strength were studied using different dosages of GAK while neat concrete was the control. Results showed that slump increased by 200% at a 2% dosage of GAK. This enabled reduction of water-to-binder (w/b) ratio from 0.61 to 0.48 for samples with a 3% dosage. Reduction in w/b resulted in increased compressive strength of 37.03% above the control after 180 days of curing for a 3% dosage. XRD studies also showed a decreased rate of hydration in the presence of GAK in concrete. It was concluded that GAK can be used in concrete as a water-reducing admixture, which is environmentally-friendly, thus producing sustainable and greener concrete.
Highlights
Concrete is a composite material made up of cement, aggregates, water, chemical admixtures and mineral admixtures
We propose use of Gum from Acacia karroo (GAK) in concrete as a water-reducing admixture
Slump test results for concrete with different dosages of GAK are shown in Table 2, including the standard deviation (SD) of the slump test measurements
Summary
Concrete is a composite material made up of cement, aggregates, water, chemical admixtures and mineral admixtures. Materials 2016, 9, 80 the natural gums, other admixtures, such as starch ether, which is a viscosity-modifying agent (VMA), lignosulfates and polycarborylate ether (superplasticizers), have been considered for use in Africa [6]. Due to their derivation process, which make them expensive, they are still not accessible to medium and small concrete consumers. Abdeljaleel et al [8] reported increased compressive strength in concrete, while [9] used it to bond sand foundry molds Both gums (GAK and GA) contain different proportions of neutral sugars. X-ray diffraction (XRD) analysis was carried out just to give an idea of hydration at 56 days
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