International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 01 | Jan 2024
p-ISSN: 2395-0072
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BATCHING METHODS AND THEIR INFLUENCE ON PROPERTIES OF CONCRETE – A LIMITED STUDY Shodolapo Oluyemi Franklin1, a, Philip N. Kaboro2 1Senior Lecturer, Department of Construction Engineering, Gaborone University College, Mmopane, Botswana. 2Formerly, Department of Civil Engineering, University of Botswana, Gaborone, Botswana.
aCorresponding Author – Email: soafranklin@gmail.com ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - The effect of mass and volume batching on the
Batching of aggregates and cement, the first stage, is defined as the process of measuring and introducing into the mixer the ingredients of the batch (Mehta and Monteiro [4]). There are generally two methods available in this regard, namely proportioning by mass or volume batching. According to Kellerman [5], Mindess et al. [1] and Mehta and Monteiro [4], batching by mass is generally accepted as the preferred means of proportioning. Since water and liquid admixtures alone can be measured accurately by volume, it is not surprising that the quantification of solids like cement and aggregates on a volume basis may result in gross errors (Mindess et al. [1]). In addition, if fluctuations or changes in aggregate moisture contents take place, proportioning by mass easily facilitates convenient and rapid adjustments of quantities of aggregate and water. According to Mindess et al. [1], environmental and practical concerns frequently make it advantageous to retain some wash water in the mixer which must be taken into account during the batching operation; this necessitates material quantities to be measured to a high degree of accuracy and is best accomplished by mass proportioning. With well- maintained and properly functioning equipment, mass batching can result in a high degree of uniformity of successive batches of concrete (Kellerman [5]).
fresh and hardened properties of concrete was investigated using a single mix proportion and water-cement or w/c ratios of 0.5, 0.55 and 0.65. Volume batching was carried out by means of a constructed gauge box, while mass batching was effected via a well calibrated mass scale. All concrete samples were manufactured using OPC 42.5N CEM Type 1 cement and the specimens were cured in water for 7, 14 and 28 days as required. It was found that the workability increased with w/c ratios for both methods of batching, although it was somewhat higher for mass proportioning than for volume batching. In addition, higher compressive strengths were obtained for concrete specimens proportioned by mass, for all w/c ratios. In most cases the coefficients of variation of the compressive strength test results for the concrete batched by mass were markedly lower than their equivalent counterparts produced by volume proportioning. It was concluded that these findings were in broad agreement with the results of previous research in the literature. Key Words: Batching method, mix proportion, watercement ratio, curing age, concrete, workability, compressive strength.
1. INTRODUCTION
In respect of batching by volume, Kellerman [5] has stated that possible sources of errors are due to the bulking of sand ranging from 15% to 30% for coarse and fine sands respectively, the compaction of aggregates and the packing characteristics of the aggregate. Regarding the latter, rounder and more graded aggregates are liable to pack more closely than poorly shaped and single sized aggregates. Major errors also occur with volume batching of cement on account of changes in the loose bulk density as the cement becomes aerated when discharged. Consequently for the foregoing reasons it is generally recommended that volume batching be confined to non-structural works such as foundations for houses, and relatively unimportant construction not requiring usage of mass batching equipment (Kellerman [5]).
Concrete is universally regarded as a composite material comprised of a mixture of coarse/fine granular materials or aggregates, cement, water and admixture all combined in certain proportions which may be varied depending on the desired nature and characteristics of the fresh and hardened concrete. The property of the fresh concrete of primary interest here is the workability, defined as the amount of mechanical work or energy needed to produce complete compaction of the concrete without segregation (Mindess et al. [1]). In a qualitative sense, the term describes the ease with which the concrete can be mixed, placed, compacted and finished (Kong and Evans [2]). With regards to the hardened concrete, the major mechanical property of concern is the compressive strength, although in several circumstances the main focus may be on the flexural and tensile strengths of the hardened concrete.
Despite the above observations and misgivings, the general tendency in many West African and particularly Nigerian construction sites is to adopt volume batching for the majority of concrete works, on the grounds of ease, simplicity and construction speed (Orumu [6]). This has been the case for both structural and non-structural concrete
The manufacture of concrete involves several steps namely batching, mixing, transporting, placing, compaction, curing and finishing in that order (Shetty and Jain [3]).
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