Suitability of Sisal Juice Extract as a Retarder in Cement Concrete

Abstract

Admixtures are used to improve the properties of concrete or mortar to make them more suitable to work by hand or for other purposes such as saving mechanical energy. Retarding admixtures are used to slow the rate of setting of concrete. By slowing the initial setting time, the concrete mixture can stay in its fresh mix state longer before it gets to its hardened form. Retarders can be formed by organic and inorganic material. The organic material consists of unrefined CaO, K2O, MgO, AL2O3, salts of lignosulfonic acids, hydroxycarboxylic acids, and carbohydrates. Agave sisalana Perrine, popularly known as sisal is a commercially used fiber yielding plant. Cement concrete production especially in hot climate experience a lot of challenges from mixing, transporting and placing of concrete because of the accelerated setting of cement concrete due to high temperatures. Workability is compromised to a large extend and there is need to prolong the setting time allow for execution of the concreting activities. The rapid heat generation from large concrete pours can also lead to cracks in the concrete structure. This results in the need to slow the rate of concreting thereby causing costly delays. Retarders go a long way in slowing down the hydration process hence reduce the heat of hydration. The study investigated the suitability of sisal juice as a retarder to influence the properties of hardened concrete at a lower cost. This research implored the use of experimental design. The study used quantitative techniques of data analysis to analyze the test results of different experiments. Descriptive statistics including means, cross-tabulation, frequencies and percentages was used for comparison and the results presented in form of frequency tables, line graphs and bar charts for easier understanding and interpretation. SJE was used as a retarder to influence the properties of fresh and hardened concrete. Sisal juice extract was used as a partial replacement of water at different dosages and in the concrete mix. A total of 84 concrete cubes were produced in 7 sets of 12no. specimen each. One set was made with the control mix which had zero SJE content. The remaining sets had varying dosages of SJE namely 5%, 10%, 15%, 20%, 25% and 30%. Twelve beam specimens measuring 150x150x530mm were also casted. Specimens were subjected to Compressive strength tests as per BS EN 12390–3:2009, setting time test as per BS EN 196-3:1995 and slump test as per BS EN 12359–2:2009. To establish the effect SJE on strength of concrete, compressive strength was tested at 7, 14, 28 and 56 days while flexural strength was tested at 28 days. The results of the tests showed that both the workability of fresh concrete and the setting times increased with increasing proportion of SJE admixture. The rate of strength gain slowed consistently for all dosages greater than 5% for curing periods beyond the 7th day. From the aforementioned, the study concluded that sisal juice extract is suitable for use as a retarder and is therefore recommended for use to compensate for high temperatures and average time for concreting operations in hot climate regions.