Concrete slump test

Concrete slump test

In construction and civil engineering, the Concrete Slump Test (or simply the Slump Test) is an in situ test or a laboratory test used to determine and measure how hard and consistent a given sample of concrete is before curing.
The Concrete Slump Test is, in essence, a method of quality control. For a particular mix, the slump should be consistent. A change in slump height would demonstrate an undesired change in the ratio of the concrete ingredients; the proportions of the ingredients are then adjusted to keep a concrete batch consistent. This homogeneity improves the quality and structural integrity of the cured concrete

Purpose
The goal of the Concrete Slump Test is to measure the consistency of concrete. Many factors are taken into account when satisfying requirements of concrete strength, and to make sure that a consistent mixture of cement is being used during the process of construction. The test also further determines the “workability” of concrete, which provides a scale on how easy is it to handle, compact, and cure concrete[3]. Engineers use the results to then alter the concrete mix by adjusting the cement/water ratios or adding plasticizers to increase the strength of the outcome concrete mix.M

Procedure
The Concrete Slump Test has witnessed many technological advances, and some countries even perform the test using automated machinery. The simplified, generally accepted method to perform the test is as follows:

Apparatus
Large pan
Trowel to mix concrete mixture
Steel tamping rod
Slump cone
Ruler
Concrete (Cement, water, sand & aggregates).

Steps
Place the mixing pan on the floor and moisten it with some water. Make sure it is damp but no free water is left.
Place the sand in the pan. Add the cement and mix it with the sand.
Add the coarse/fine aggregate and thoroughly mix.
Mix the water and dry cement ingredients thoroughly using the trowel.
Firmly hold the slump cone in place using the 2 foot holds.
Fill one-third of the cone with the concrete mixture. Then tamp the layer 25 times using the steel rod in a circular motion, making sure not to stir.
Add more concrete mixture to the two-thirds mark. Repeat tamping for 25 times again. Tamp just barely into the previous layer(1")
Fill up the whole cone up to the top with some excess concrete coming out of top, then repeat tamping 25 times. (if there is not enough concrete from tamping compression, stop tamping, add more, then continue tamping at previous number)
Remove excess concrete from the opening of the slump cone by using tamping rod in a rolling motion until flat.
Slowly and carefully remove the cone by lifting it vertically (5 seconds +/- 2 seconds), making sure that the concrete sample does not move.
Wait for the concrete mixture as it slowly slumps.
After the concrete stabilizes, measure the slump-height by turning the slump cone upside down next to the sample, placing the tamping rod on the slump cone and measuring the distance from the rod to the ORIGINAL DISPLACED CENTER.

First pile -Halfaya bridge

First pile was casted on 12- APRIL-2008

Cable-Stayed Bridge

Radial attachment pattern

Parallel attachment pattern

Cable-Stayed Bridge

Cable-stayed bridges may look similar to suspensions bridges—both have roadways that hang from cables and both have towers. But the two bridges support the load of the roadway in very different ways. The difference lies in how the cables are connected to the towers. In suspension bridges, the cables ride freely across the towers, transmitting the load to the anchorages at either end. In cable-stayed bridges, the cables are attached to the towers, which alone bear the load.The cables can be attached to the roadway in a variety of ways. In a radial pattern, cables extend from several points on the road to a single point at the top of the tower. In a parallel pattern, cables are attached at different heights along the tower, running parallel to one other.

Proctor compaction test

Proctor compaction test

The Proctor compaction test and the related modified Proctor compaction test, named for engineer Ralph R. Proctor (1933), are tests to determine the maximum practically-achievable density of soils and aggregates, and are frequently used in geotechnical engineering.
The test consists of compacting the soil or aggregate to be tested into a standard mould using a standardized compactive energy at several different levels of moisture content. The maximum dry density and optimum moisture content is determined from the results of the test.
Soil in place is tested for in-place dry bulk density, and the result is divided by the maximum dry density to obtain a relative compaction for the soil in place.

History and its origin
Proctor's fascination with geotechnical engineering began when taking his undergraduate studies at University of California, Berkeley. He was interested in the publications of Sir Alec Skempton and his ideas on in situ behavior of natural clays. Skempton formulated concepts and porous water coefficients that are still widely used today. It was Proctor’s idea to take this concept a step further and formulate his own experimental conclusions to determine a solution for the in situ behaviors of clay and ground soils that cause it to be unsuitable for construction. His idea, which was later adopted and expounded upon by Skempton, involved the compaction of the soil to establish the maximum practically-achievable density of soils and aggregates (the "practically" stresses how the value is found experimentally and not theoretically).
In the early 1930s, he finally created a solution for determining the maximum density of soils. He found that in a controlled environment (or within a control volume), the soil could be compacted to the point where the air could be completely removed, simulating the effects of a soil in situ conditions. From this, the dry density could be determined by simply measuring the weight of the soil before and after compaction, calculating the moisture content, and furthermore calculating the dry density. Ralph R. Proctor went on to teach at the University of Arkansas.

Soil compaction
Compaction is the process of increasing the bulk density of a soil or aggregate by driving out air. For any soil, for a given amount of compactive effort, the density obtained depends on the moisture content. At very high moisture contents, the maximum dry density is achieved when the soil is compacted to nearly saturation, where (almost) all the air is driven out. At low moisture contents, the soil particles interfere with each other; addition of some moisture will allow greater bulk densities, with a peak density where this effect begins to be counteracted by the saturation of the soil.

Different tests
The original Proctor test, ASTM D698 / AASHTO T99, uses a 4-inch diameter mold which holds 1/30th cubic foot of soil, and calls for compaction of three separate lifts of soil using 25 blows by a 5.5 lb hammer falling 12 inches, for a compactive effort of 12,400 ft-lbf/ft³. The "Modified Proctor" test, ASTM D1557 / AASHTO T180, uses the same mold, but uses a 10 lb. hammer falling through 18 inches, with 25 blows on each of five lifts, for a compactive effort of about 56,000 ft-lbf/ft³. Both tests allow the use of a larger mold, 6 inches in diameter and holding 1/13.333 ft³, if the soil or aggregate contains too large a proportion of gravel-sized particles to allow repeatability with the 4-inch mold. To ensure the same compactive effort, the number of blows per lift is increased to 56.
The California Department of Transportation has developed a similar test, California Test 216, which measures the maximum wet density, and controls the compactive effort based on the weight, not the volume, of the test sample. The primary advantage of this test is that maximum density test results are available sooner, as evaporation of the compacted sample is not necessary.
There is also a test (ASTM D4253) which uses a vibrating table using standard vibrations for a standard time to densify the soil. This test method prevents particle breakage, but is only usable for granular soils. The test method also includes a method to determine the minimum density of the soil; density of soils in place are compared against the maximum and minimum to obtain a relative density.

Launching Girder

Launching Girder

Bridging by Segmental Box Girder

Bridging by Segmental Box Girder

SEGMENTAL BOX GIRDERS SYSTEM
Introduction.
Segmental box girders (segments) system is used for building superstructure for bridges / other structure in replacement of conventional construction via pre-cast beams and cast-in-situ decks. Segments will be pre-cast at another location preferably at outskirts of city. New setup of casting shall be done specifically to carry out the segments casting works. Segments are cast using specific moulds as the shape and dimension are also specific. Moulds may be made out of cut and weld steel sections and other accessories to complete the moulds. The cast segments later shall be brought to site and erected at specific location via launching girder system (or other method) by continue joining segments to each other to form the completed decks in between of two piers. Post tensioning in form of stressed groups of strand wires shall keep the segments together and provide the strength required to support the required loading on the deck. Further works can then be carried out as per requirement prior opening to users.

Advantages of using segmental box girders system (comparing to conventional method)
The segments system reduces the environmental disturbance compare to the conventional method by carrying out the concreting works further away from the construction site where is usually located at city centers.
Quality can be maintained since the casting of segments shall be carried out at control environment as compared to carry out at site.
Aesthetic of using segments system is better due specific shape can be cast if so required by clients.
Since segmental box girders are pre-cast elements, casting of segments can proceeds while piling works, pile-caps, piers, pier caps construction are proceedings at site. Therefore, shorter duration of construction is achievable.

Ameria Bridge 2001

Ameria Bridge Construction