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  • In this study the ASTM C and ASTM


    In this study, the ASTM C1260 and ASTM C1567 test methods were followed to conduct the ASR tests. Three mortar bars were prepared using three types of RHA (600-RHA, 150-RHA, and 44-RHA) and CFA. To prepare the mortar bars, the OPC was replaced by each type of RHA for 10% and 20%, respectively by weight and compared with control mortar bars (0% RHA). During the test, the length change of each mortar bar was determined by taking intermediate readings at 4, 8, 12 and 14 days. A linear variable differential transducer (LVDT) was used to take measurements with the help of a data storage unit (Fig. C.2). Routine test results (e.g., workability, air contents, compressive strength, tensile strength) of tested RHA- and CF-modified concrete of the current study have been reported elsewhere in the literature [17], [19]. Slump values of fresh concrete were about the same for the control and 10% RHA-modified concrete, whereas 20% RHA-modified concrete exhibited a higher slump value. An increment of the RHA percentage also increased the air voids, but it decreased the unit weight. It happened as the OPC was significantly finer than the RHA. Coarser particles of RHA created additional air voids in the concrete, which eventually decreased the unit weight of the fresh concrete.
    Result and discussion
    Introduction Biologically produced surfactants are amphipathic molecules integrated into the cell membrane or extracellularly secreted into the environment. All surfactant molecules share a basic molecular structure that includes a polar “head” group and a non-polar “tail” group. The GSK 2837808A mg functional head group and the hydrophobic alkyl chain tail are self-organized at liquid to liquid, gas and solid interfaces (Satpute et al., 2010). Bacteria, yeast, and fungi are capable of producing biosurfactants. Biosurfactants are potential replacements for synthetic surfactants in several industrial processes, food, biomedical and pharmaceutical industries, as well as bioremediation of chemical-contaminated sites. Glycolipids and lipopeptides are the most important commercial biosurfactants (Shah et al., 2016). It was estimated that there were more than 255 patents issued on biosurfactants and bioemulsifiers (Cameotra and Makkar, 2010). Biosurfactants have been widely used in the petroleum industry, cosmetics, antimicrobial agent, medicine and bioremediation (Singh et al., 2008). Many biosurfactants was identified as rhamnolipids (RLs) which have been extensively studied. RLs are glycosides that are composed of a glycon and an aglycon part linked to each other via O-glycosidic linkage. The glycon part is composed of one or two rhamnose moieties linked through α-1, 2-glycosidic linkage (Edwards and Hayashi, 1965). The aglycon part consists mainly of one, two or, in few cases, three β-hydroxyfatty acid chains (Andra et al., 2006); these fatty acid chains are most commonly saturated or, less abundantly, mono- or polyunsaturated. Their chain lengths vary from eight carbons (C8) to sixteen carbons (C16) (Abalos et al., 2001). These fatty acid chains are linked through an ester bond formed between the β-hydroxyl groups of the distal chain (relative the sugar part) with the carboxyl group of the proximal chain. RLs are mainly produced by Pseudomonas species. Other bacteria species are also able to produce RLs, including Renibacterium salmoninarum (Christova et al., 2004), Cellulomonas cellulans (Arino et al., 1998), Nocardioides sp. (Vasileva-Tonkova and Gesheva, 2005), and Tetragenococcus koreensis (Lee et al., 2005). However, few Burkholderia species have been reported for rhamnolipid production (Abdel-Mawgoud et al., 2010). To date, about 60 different RL congeners and homologs have been reported, as recently reviewed by Abdel-Mawgoud et al. (2010). While Pseudomonas aeruginosa synthesizes a mixture of mono- and di-RLs with hydroxy-acyl moieties mostly from C8 up to C12 (Bharali and Konwar, 2011), Burkholderia sp. produce principally di-RLs with two rhamnose units and mainly C14 hydroxy-acyl chains. To our knowledge, no C16 -C16 rhamnolipids were reported in the literature.