Fine and Coarse Aggregates in Concrete Gradation - Essay Example

Introduction Essentially, aggregate comprises of granular materials such as gravels, cracked stones and other small grainy substances. The shrinkage factor of aggregate will reduce the cost of materials such a concrete at greater length thus can influence the strength, durability as well as density of toughened concrete.Some of the aggregates used in concrete and how it affects the overall strength and performance are discussed.American Society for Testing and Materials (ASTM) is one of the commonly used standards to analyse the aggregate properties and methods such as test, classifications as well as recommended specifications and practices.

Any aggregate that should be used for any construction must be based on certain quality information. Such information can be obtained after experimental tests have been done on the sample and measured to ascertain its standards. Basically, ASTM C33 is one of the accords for concrete specification for both fine and coarse aggregates (Ward, 2004).Objectives The report is aimed to find the fineness modulus for both fine and coarse aggregateResults 1. Sieve fine aggregate analysisFrom the graphs, the fineness modulus can be obtained for both coarse and fine aggregates.

Normally, the entire mass of the material should correspond with the original mass after sieving and should not be greater than 0.3%.If the results is greater than that value, then it should not be used because it will have exceeded the acceptance level (Ward, 2004).Calculation for fineness modulus is given by:=Percentage of Individual Fraction Retained, By WeightCumulative Percentage Retained, By Weight000.80.80.51.30.41.71.63.325.528.857.185.915.7101.6Sum total 221.1Therefore; fineness modulus is equivalent to Figure 1: Fine aggregate curve2.

Coarse aggregate analysisSimilarly, the fineness modulus for coarse aggregate can be obtained.Sieve Size (mm)Cum. Percentage Retained25.40 19.053 12.736 9.52559 4.7581 Pan99 Sum total 278The fineness modulus is therefore; Figure 2: coarse aggregate curveDiscussionAccording to ASTM C 33, an aggregate which can fail to meet the sieve analysis provisions might be accepted, that is if it validates that the concrete prepared with such fine aggregate will have crucial properties andshould comply specific requirements.

On the other hand, when a specified grading is chosen, close control should be done in order to minimise disparity. If a wider deviation is used in coarse aggregate ensued on a certain project, it is recommended to adjust the mix proportion in order to obtain a workable and effective concrete (Ward, 2004).Similarly, small or fine aggregate grading potentially can affect the workability aspect of the concrete owing to its large surface area.Finally, the ASTM C 33 requires that, for any ongoing consignments from any source, the fineness modulus of a fine aggregate should not be more than 0.20. Furthermore, if the fineness modulus is very much different from that used in selection of proportions, then adjustments should be made in ratios of fine and coarse aggregates.

Maintenance of uniformity in production of aggregates is more economical and cheap than adjustment of variations in grading.ConclusionFrom the analysis discussed above, the fineness modulus obtained for fine aggregate is 2.211 while for the coarse aggregate is 2.78.It can be deduced that the fineness modules depends on the coarser or softness of the material. The coarser the aggregate the higher the fineness modulus, similarly the finer the aggregate the lower the fineness modulus.An ASTM C33 specification stipulates the fineness modulus of sands in concrete.

Fundamentally, according to their standards, the fineness modulus for sand in concrete ranges from 2.3 to 3.1.Conclusively, from the results obtained the fineness modulus for fine sand is slightly lower than the expected value while that for the coarse aggregate is within the range.References Ward, R. Malis. "Aggregates For Concrete." Materials for Concrete Construction (2004).