Maximum Size Of Coarse Aggregate Research Articles

Workability of gap-graded versus continously-graded concrete and the correlation of slump with Vebe time

The workability of both gap-graded and continuously-graded concretes of various mixture proportions has been measured concurrently by the slump of a standard cone and by a Vebe consistometer. The results are compared for both concretes on the basis of equal maximum size of coarse aggregate, water-cement ratio, and aggregate-cement ratio. The comparison has shown the relative ease of placing gap-graded concrete to attain uniform compaction. Based on test data, a comparative study of the efficacy of slump test versus Vebe time as a measure of workability has been made. The slump test is not fully indicative of the workability for stiffer mixtures with slump less than one inch (2.54 cm) which should be normally used for obtaining economical high-strength concrete. It further indicates that the Vebe consistometer should be used, instead, in all stiff mixtures.

An Experimental Study on the Maximum Size of Coarse Aggregate in Asphaltic Concrete

It is the main purpose of this study to ascertain whether or not the maximum size of coarse aggregate will affect the stability of asphaltic concrete and the optimum percentage of its coarse aggregate.In this study, crushed stone, natural river sand and limestone powder were used for aggregate. The maximum sizes of crushed stone were 25, 20, 13 and 10mm. The percentages of coarse aggregate (>2.5mm) were 65, 60, 55, 50, and 45. The asphalt content varied from 5.5% to 9.5%. The properties of asphalt mixtures were evaluated by the Marshall test.The main conclusions to be drawn from the date obtained are as follows:(1) The maximum size between 13 and 25mm had negligible effect on the Marshall stability, whereas considerable reduction in stability was obtained when 10mm size was used. Therefore, 13mm size can be used for dense-graded asphaltic concrete.(2) The maximum size between 10 and 25mm had little effect on the optimum percentage of coarse aggregate. Consequently, it is not necessary to change the ratio of fine aggregate to coarse aggregate, when 13mm size is used instead of 20mm size.(3) The authors regard the specific limit of Japan Road Association for gradation of overall aggregate of dense-graded asphaltic concrete as appropriate.

Some fatigue tests of high-strength concrete in axial compression

Summary A programme of tests was undertaken of concrete prisms in axial compression to study the influence of the static strength and the maximum size of coarse aggregate upon the fatigue strength at one million cycles. Four types of concrete were tested having average static strengths of about 6,000 and 8,500 lb/in2, each made with aggregate of ¾ and ⅜ in. maximum size. The fatigue strength varied between 66 and 71 % of the static strength and, although the percentage values were significantly lower with the higher-strength concrete and with the ⅜ in. aggregate, the actual magnitude of the differences was small. The general strain history was typical of previous fatigue tests, and the ‘run-out’ specimens showed a marked increase in static strength over similar specimens that had not been loaded.

AEレデー・ミクスト・コンクリート中の空気量

This paper presents the result of test conducted by means of Air-Meter for the purpose of measuring air content on the concrete produced at both the Ikebukuro and Narihirabashi Plants of our company.(1) Air content per cubic meter in case the quality and quantity of AEA, cement, aggregates used are maintained constant:The concrete tested was these manufactured at our plants during one year from Oct. 1952 to Sept. 1953. Vinsol. Resin used 0.75% of cement, and cement used more than 300kg for the concrete per cubic meter. Fine aggregates used are of same province and nearly 2.2 fineness modulus, while the maximum size of coarse aggregates which have nearly 9.8 of fineness modulus, is 25mm. Also distributing state of air was investigated for three different slumps ranging from 0-10, 10-20 and above 20 without considering of temperature.(2) Variation of air content for every month when concrete was placed:Of the results of air test made from Jan. to Sept. 1953 without reference to ratio of fine and coarse aggregates, taken into consideration was a concrete containing 250kg of cement per cubic meter. The results was that 47.9% of concrete contains 4+0.5% of air, 77.6% of concrete 4+1.5% of air and 92% of concrete, 4+1.5% of air as given in Table 6.From the above, several problems such as variation of air content for different fineness of fine aggregates, selection of sample for air test and possibility of adding AEA into paste were investigated.