Compaction effort

Mix design is the choice of the best combination of aggregate, binder, and compaction effort to produce desirable pavement material properties. The choice has been made normally based on the results of simple indicator and control tests such as the Marshall stability, Marshall flow, Hveem stability, resilient modulus, and indirect tension tests. 

An Efficient Method of Mix Design. The best combination of aggregate properties, sulfur and asphalt quantities, and compaction effort may be considerably different in a sulfur-asphalt mix than in conventional asphalt concrete. Since there is little available field or laboratory experience to borrow upon, an experimental design procedure may be adopted to use laboratory experimental data most efficiently in determining the best mix. 

Compaction effort variables of 0.1 and 1.0 indicate compaction efforts of 2 and 75 blows per face, respectively. 

Cone Penetration Test, CPT. See ASTM Standards D-1586 and D-3441. Field density tests are used extensively to determine if modification is needed and to monitor the progress and results of modification (compaction) efforts. 

Figure 3.1 shows typically that for any soil as the compactive effort increases, the maximum density increases and the optimum water content decreases. The approximate relative moisture density relationships for the soil designations of the Unified Classification System are shown in Figure 3.2. 

Test No. Designation Number of layers Weight of hammer, lbs Height of drop, in. Number of blows/layer Compactive effort, in ft-lbs/ft ... 

No problems with dusting or auto-ignition were noted. The material was spread in 20-30 cm layers and subjected to various compactive efforts. Approximately 1200 m3 (15000 tonnes) of retorted shale was used in these field compaction studies. 

Compaction. The field compaction studies confirmed earlier laboratory studies regarding the effect of compactive effort, moisture addition, and aging on density and strength. Shown in Figure 4 is the relationship of compactive effort on the densities of retorted shale. At least three in-place density measurements were made in each layer. Results show that densities averaging 1400 kg/m3 (about 95 lb/cu. ft.) can be achieved. 

Continuous grading of mineral particles, yielding low porosity mixtures with little compactive effort, are of great importance in concrete technology and soil engineering. Most widely used for this purpose are the gradation curves by Fuller and Thompson and the nearly equivalent formula by Rothfuchs ... 

Measure the mass (or weight) of solids per unit volume of soil. Often used as a quality control for compaction of fill Indicate the degree of compaction that can be achieved at different moisture contents with different compactive efforts Density index indicates the stiffness and peak strength of coarse grained soils. A number of different methods are available, so the method used should be clearly stated... 

Determines compactive effort required to produce near-full compaction. Used for control of materials for earthworks... 

Proctor, RR. (1948). The relationship between the foot pounds per cubic foot of compactive effort and the shear strength of compacted soils. 2 Inti. Conf. Soil Mechanics and Foundation Engineering Rotterdam 5 219-223. 

The moisture content that gives the maximum dry density is defined as optimum moisture for maximum compaction. Needless to say, the use of less compaction effort would result in different optimum moisture contents and, of course, less dry compacted density (see curve B, Figure 1.4). 

As mentioned earlier, there is a strong relationship between compaction effort, moisture content and density. 

The moisture condition value (MCV) test involves testing a soil material at fixed moisture content but by different compaction methods (number of blows or by a vibratory rammer). Thus, the compaction effort beyond which there is no further increase in density is determined. This test is much newer than the proctor test it has been developed in the United Kingdom (Parsons 1992) and is also used by some other countries. 

The method was developed by the California Road Service in the 1930s and has since been adopted by many administrations/organisations around the world. The original test method has been slightly modified by some organisations. The modifications were mainly concerned on the moisture at compaction and on the compaction effort. The procedure, however, in determining the CBR value remained unchanged. 

Design CBR is usually defined by the relationship between CBR and the dry density of compacted soil material. The results of the three specimens compacted at different compaction efforts (number of blows), and thus having different densities, are presented in Figure 1.8. 

The advantages of high-compaction screeds are as follows (a) they minimise the compaction effort on subsequent compaction equipment to achieve the required densities, (b) they open up the possibility of single-layer construction of thicker layer and (c) they minimise the effect of environmental factors on the cooling of asphalt mat. 

Aggregates, with respect to their particle size distribution, shape and surface texture, directly affect the asphalt workability/compatibility. Open-graded mixtures have better workability and require a smaller compaction effort than dense-graded mixtures. Additionally, an increase of coarse aggregate content reduces the workability and increases the compaction effort. 

Effective compaction is related to the type of compaction equipment used. Asphalt layer compaction equipment consists of self-propelled vehicles, known as rollers, which compact the asphalt layer by the effect of their self-weight or by additionally imposing dynamic loading. The desired compaction is achieved by applying a certain number of passes of the rollers over the asphalt layer, known as compaction effort. 

Embankment soils need to develop high shear strength, low permeability and low water absorption, and undergo minimal settlement. This is achieved by compaction. The degree of compaction achieved is reflected by the dry density of the soil. The relationship between dry density and moisture content of a soil for a particular compactive effort is assessed by a compaction test. 

Explain... how Standard and Modified Proctor compaction tests are performed and define the term compactive effort. (2)... 

A sandy clay (ps = 2. JOMg/rn ) from the San Luis Obispo area was placed at a water content of 14 percent and compacted to a dry density of 1.66Mg/m. Evaluate the in-place soil conditions. The as-compacted soil is most likely (a) dry of optimum, (b) wet of optimum, or (c) at optimum for the compactive effort actually employed in the field ... 

When defined or specifying the required strength of a fill mass, a fundamental choice has to be made. A choice can be made for a high strength. This may result in a lot of compaction effort, but will possibly lead to a smaller and/or cheaper foundation design. 

This laboratory test was developed to deliver a standard amount of mechanical energy (compaction effort) to determine the maximum dry density of a soil. The test was initially intended for more or less cohesive soils, whereby the water content is greatly affecting the dry density after compaction. 

Figure 4, from Zekkos et al. (2006), provides a family of typical unit weight profiles for MSW landfills that depend upon the amotmt of cover soil and compaction effort provided by the landfill operator during waste placement. Due to difficulties in measuring the waste unit weight in the... 

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