Slump Test

Slump Test

Standard test method for the slump of hydraulic cement concrete. (ASTM C-143/C-143 M-03)

Scope & significance:This test method is used in lab and in field for finding out the slump (decrease in the height of concrete when we lift up the mould). This test is used extensively in site works all over the world. The slump test does not measure the workability of concrete directly but it co-relates the workability with some physical measurement.The main significance of this test is as follows;This test method is used to determine the slump of plastic hydraulic cement concrete.

Slump <15mm (Non-Plastic)
Slump>15 (Plastic)

This test method is applicable to plastic concrete having coarse aggregate upto 37.5mm in size. If the coarse aggregate is larger than the 37.5mm then this test method is not applicable.This test method is not applicable to non-plastic and non-cohesive concrete (due to larger amount of water presence).

Apparatus:
                    

                     1-     Metal mould, thickness is 1.15mm, it is in cone form with the base 200mm diameter and 300mm height with the top diameter 100mm. the top and base of cylindrical mould is open and parallel to each other. The mould is provided with foot pieces and handles.

                     2-      Temping rod, 16mm diameter and 600mm in length having temping ends.Related theory:SlumpThe decrease in the height of concrete when the mould of standard dimensions is lifted.Types Of SlumpThere are three types of slump.

1-      True Slump
2-      Shear Slump
3-      Collapse slump

We discard the collapse slump due to the very high value of slumpShear slump occurs due to the lack of cohesion in mix.
We often use the term 100% compaction but actually in 100% compaction we have percentage of air voids less than 3% by volume of concrete.

Workability Compacting Factor
Slump (mm)

Very Low     0.780 – 25

Low              0.8525 – 50

Medium      0.9250 – 100 

High             0.95100 – 175

Note: More is the slump value more will be the workability.

Procedure:

The mould is placed on a flat moist non-absorb surface with the smaller opening at the top. It is then held firmly in place during filling of concrete by the operator standing on two foot pieces. The mould is filled to a depth of 70mm and 2/3 of volume fills to a depth of 160mm. Each layer is given 25 strokes with the help of temping rod uniformly distributed over the cross-section of each layer. Rod the 2nd and 3rd layer through out its depth so that strokes just penetrates into the under lying layer. After the top layer is rodded strike off the surface of the concrete by means of rolling motion of temping rod. Complete the entire test with an elapsed time of 2.5minutes. After filling, the cone is slowly lifted and the unsupported concrete slumps. The decrease in the height of concrete is called slump.  It is measured with the nearest 5mm. at the beginning of every test, before lifting the mould the area immediately around the base of the cone should be cleaned off of concrete which may be dropped accidentally.

The minimum value of slump = 1”= 25mm
The maximum value of slump = 4” =100mm
Results: Slump Value =  …75…  mm

Comments:
        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. From the performed experiment we came to know that our mean slump value was 75mm which describes that it is True Slump and its workability is medium

Foundation Crack – Cost of Cracked Foundation Repair

Cracked foundations can be disastrous for a structure. The most common cause of a cracked foundation is settlement. As the foundation shifts and settles into the ground over time, cracks can occur. Depending upon the severity of the settlement the cost of cracked foundation repair will vary.House foundation crack

__________________________Cracked Foundation Repair Average Cost___________________________

The average cost of cracked foundation repair will range between $5,000 and $7,000. This is considered a base price and does not account for any unforeseen problems when the contractor begins work. If the foundation is heavily damaged, the cost of repair can be over $10,000. You also might be interested in our article on foundation construction requirement.

__________________________What to do if you found cracks in foundation_________________________

The process of repairing a cracked foundation generally includes a formal inspection. This is where an official inspector will assess the cracks and then they will recommend the next step which usually involves bringing in a structural engineer if the cracks are problematic. You may be lucky enough to only need a mason to fix a few cracks, but generally if the cracks are so noticeable that they need repaired; it is beyond the stage of a quick, cheap fix.Foundation CracksIf the work will be extensive, it is best to get estimates from contractors so you know you are getting the possible repair for your money. Contractors need to be licensed and insured before working on foundations.If the repairs that need to be made a basic and just need patch work completed, then the cost could be as low as $500. Basic repairs on a cracked foundation will not generally go over $2,000 unless bigger issues are found during the repair process.If the repairs that need to be made are major or extensive, the cost will range between $5,000 and $7,000. This depends on the type of work that is required to fix the foundation. However, if the project requires excavation and pouring of new sections then the cost will reach over $10,000.

________________________________________________Why Foundation Cracks___________________________________________

Foundations crack for various reasons. Settlement is the biggest reason that they crack. It is always best to keep a check on the foundation of a building regularly and repair any crack that presents before it becomes problematic and costs thousands of dollars to repair.

Pool Excavation – How To Excavate a Swimming Pool

Excavating a swimming pool takes a lot of work, heavy machinery and knowledge of how to excavate a pool. Most people will hire a professional to complete the pool excavation. When hiring a pool excavator be sure to thoroughly check their business out and make sure that they possess the right credentials.

Swimming Pool Excavation: Step by Step Guide

Before starting pool excavation, you should know what you are doing and if it is the right process. So here are step by step procedure described below to give you a clear idea about pool excavation process.

Step 1: Permits and Permission

Prior to beginning the excavation acquire all necessary permits from your county to ensure that you are in compliance. If you will be encroaching upon a neighbor’s property or you need to use part of their property to access the area for the pool, be sure to get their permission first. It is always best to get written permission. Post all permits prior to starting any work.

Step 2: Underground Cables

Prior to doing any digging, contact the electric company and have them come to the site to mark where underground cables are located. If you have underground cables for television or internet, be sure to also contact that company to mark where those cables are located.

Step 3: Pool Layout

Not all swimming pools are the same size or shape. The layout sub-contractor will have to paint a guide for the excavators so they dig the appropriate dimensions. Make sure the level that the top of the pool will finish is clearly identified.a swimming pool

Step 4: Digging

When able, use the biggest machine possible as it will move the dirt with more efficiency. By being more efficient, it should also be less costly as it takes less time to excavate the area. Using a dumpy level or water level will help check the depth of the excavation at various points along the floor. It is best to dig from the deepest point to the shallowest. The mark-out for the shape of the pool needs to be six inches outside the finished internal line of the pool.an example of swimming pool excavation

Step 5: Remove Dirt Dug

Never leave the dirt that has been dug from the pool area on site. The only exception is if you have another immediate use for the dirt. By leaving the dirt in the yard, it will be in the way of the excavator and those installing the actual pool. The work site will not remain clean with piles of dirt around.

Step 6: Smooth the Walls

Once the digging and dirt removal are finished, it is time to smooth out the floor and walls so that pool will sit evenly in the excavated spot. Not smoothing out the floor and walls will cost you time and energy when the actual pool arrives as it will not fit correctly into place.

Step 7: Pool Placement

Once the excavation is complete, then the proper enforcers will come out and inspect the area. Once the safety inspector signs off on the project at this phase, it is time to bring in the actual pool for proper placement.Finally, pool excavation work needs some expertise and it is best to do the construction work by a professional person.

Concrete Shrinkage | Types, Factors Affecting and Where Concrete Shrinkage Occurs

Concrete shrinkage can become problematic when doing any type of construction, but especially when dealing with floors. Concrete shrinkage is the contracting of the concrete due to the water evaporating from the mixture. This evaporation will cause the concrete to weaken. This can lead to cracks, internal warping and external deflection.

Types of Concrete Shrinkage

There are numerous types of concrete shrinkage including plastic shrinkage, drying shrinkage, autogenous shrinkage, and carbonation shrinkage.

       ★ Plastic shrinkage happens soon after the concrete is poured in the forms. The water evaporates and results in a reduction of volume, this causes the concrete on the surface to collapse. It can be reduced by covering the surface with polyethylene sheeting immediately after it is poured.

     ★  Drying shrinkage is the ever lasting process for concrete within drying conditions. The loss of water within the gel pores of the concrete is what causes the concrete to shrink. The finer the gel within the pores, the more shrinkage there is.
     
     ★  Autogenous shrinkage is most prevelant within the concrete in the interior of a dam. When the temperature is constant shrinkage may occur, especially when there is no moisture movement.
     
     ★  Carbonation shrinkage is where carbon dioxide penetrates beyond the surface of the concrete. This also depends on the moisture content and the humidity levels. Carbonation shrinkage is caused by the disbanding of calcium hydroxide crystals and the evidence of calcium carbonate.

Factors Affecting Shrinkage

There are so many factors that affect the shrinkage of concrete. The most important factor is the drying condition or the humidity in the atmosphere. No shrinkage will occur if the concrete is placed in one hundred percent relative humidity.The shrinkage rate will decrease rapidly with time. It has been documented that fourteen to thirty-four percent of the twenty year shrinkage will occur within two weeks of it being poured. Within one year of the concrete being poured, shrinkage will be about sixty-six to eighty-five percent of the twenty year shrinkage.The water to cement ratio will influence the amount of shrinkage that occurs. The concrete’s richness also affects the shrinkage. The process of swelling and then drying affects the concrete’s integrity and the shrinkage. You can also read about sulfate attack on concrete here.

Where Concrete Shrinkage Occurs

Concrete shrinkage can occur in any poured concrete. It is most common in slabs, beams, bearing walls, foundations and columns. It can also be found in pre-stressed members as well as tanks. Shrinkage is a problem for any poured concrete, but when it happens in bearing walls and foundations the entire stability and integrity of the structure is in jeopardy.

Concrete Bleeding | Causes, Problems and Remedies For Bleeding

Concrete bleeding is defined as the appearance of water on the surface of concrete after it has consolidated but before it is set. This is a type of segregation where water appears at the concrete surface after placing and compacting, but before it is set. Water may also form a film under aggregate and reinforcing bar. Some bleeding is useful for finishing operations and to reduce plastic shrinkage cracking.

Problems due to Concrete Bleeding

Concrete bleeding can cause problems including the followings.It can delay in finishing.Bleeding of concrete can cause high water-cement ratio at the top.It will result in poor bond between two layers.It can result in poor pump ability.

Concrete Bleeding Causes

◆ Bleeding of concrete occurs due to the causes stated below.
◆ The lack of fines,
◆ Too much water content in the mix.

Bleeding Remedies

◆ Remedies for bleeding of concrete are as follows.
◆ More fines,
◆ Adjust grading,
◆ Entrained air,
◆ Reduce water content.

Soil Stabilization | Why Soil Stabilization is Used and Methods Used for Soil Stabilization

Soil stabilization is the process which is used to improve the engineering properties of the soil and thus making it more stable. Soil stabilization is required when the soil available for construction is not suitable for the intended purpose. It includes compaction, preconsolidation, drainage and many other such processes.soil stabilization techniques

Uses of Soil Stabilization

It is used for many purposes. It increases different soil properties as listed below.Soil stabilization is used to reduce the permeability and compressibility of the soil mass in earth structures and to increase its shear strength.It is used to increase the bearing capacity of foundation soils.It is used to improve the natural soils for the construction of highway and airfields.It is also used to make an area trafficable within a short period of time for emergency purposes.Soil stabilization is used to increase the unit weight of the soil.It helps to decrease the void ratio of the soil.Stabilization of soil increases the shear strength of soil.

Soil Stabilization Methods

Different soil stabilization techniques are used all over the world. These soil stabilization methods are listed below.

★ Cement stabilization
★ Lime stabilization
★ Chemical stabilization
★ Bituminous stabilization
★ Grouting concrete stabilization
★ Geotextile stabilization
★ Reinforced earth stabilization.

Slab on Grade Foundation – Advantages, Disadvantages and Uses of Slab Foundations

Slab on grade foundations are also commonly known as floating slab foundations. The foundation is formed using a mold that is set into the ground rather than digging a basement for the structure. There is no space between the ground and the poured concrete.

Uses of Slab Foundations

Slab foundations are used under the following conditions.Slab foundations are usually found in warmer climates. The freezing and thawing effect on the ground is not a concern in warm climates. This negates the need for heat ducts under the floors.They are very common in areas that are comprised of clay soil.These foundations are the general accepted foundation for tract homes or buildings being quickly built with a low budget.Slab foundations are used for sheds, barns and garages to give a sturdy floor without putting out a lot of extra money.slab foundation – example 1

Advantages of Slab Foundations

Slab foundations have many advantages.
The advantages of slab foundations are listed below.It is inexpensive.
The cost is significantly less than doing a full basement or even a crawl space under a building.
They are sturdy. The building is resting directly on the poured concrete and is not relying on beams and other supports to sustain the building.
Termites are not a problem. With a concrete slab foundation, there would be no wood touching the ground and being potentially exposed to termites.
They are an excellent solution for tract homes considering their cost effectiveness.
Slab foundations are excellent for flooring in a shed,
garage or barn.Labor costs, forms and excavation are at a minimum.
This keeps the costs down and allows for quick builds.

Disadvantages of Slab Foundations

Slab foundations also have some disadvantages that should be considered.
The disadvantages of slab foundation includes the followings.
No access underneath the slab for utility lines and other important cables.
Heat loss occurs quickly when the ground temperatures fall below the temperature inside the building.
Floods are a concern. If the slab foundation is located at a low elevation the building can flood even in mild rains.
Extending the building is not generally possible since it is sitting on a poured concrete slab.
Slab foundations will settle over time and create problems with the soundness of the building.
Natural gas and water lines that are laid when the slab is poured will eventually break down over time and will need to be replaced.                                              It is impossible to check the pipes regularly so you must watch for signs of a leak. These include wetness on the floor,                                                     water pressure dropping and exterior walls being discolored.
settling of slab on grade foundationSlab on grade foundations require that all plumbing and electrical be placed below grade or inside the building.
All wiring must be placed within water tight conduit and have the ability to be replaced when upgrades or repairs need to be made.
While slab on grade foundations are inexpensive and make building go more quickly, the disadvantages outweigh the advantages.
For homes, it is best to have a different foundation poured rather than deal with the problems that could occur with a slab on grade foundation

Garage Foundation: How To Build Foundation For a Garage

Garage Foundation construction can be tricky if you do not have a general knowledge on construction and construction materials. There are specific steps that need to be taken to ensure that the garage foundation is sturdy and will hold the weight of the garage structure plus the weight of the vehicle that will be housed there.

How to Build a Foundation for Garage

Here are 6 steps to guide you the process of garage foundation construction.

Step 1: Pick the Type of Foundation

This will depend mainly on the area that the foundation will be located and the type of garage that will be placed on it.Shallow foundations are used for ground that is level and the surface is hard. These are no more than three feet deep and are used for smaller projects such as sheds or garages that will not hold large vehicles.Deep foundations are used when the soil is in poor condition or the structure is being built on a hill. These are deeper than three feet deep and will have depths that vary throughout the foundation. They are used for complex projects and garages, such as a detached garage, that will house larger or heavier vehicles.

Step 2: Set the Footings

Footings need to be set two feet across and then add two feet on each side. This method properly spaces the form and gives the necessary space to lay the foundation properly.

Step 3: Alignment of Forms

The boards need to be aligned two inches wide by ten inches long. This gives a sturdy form for the footings. Once you have the foundation shape and size mapped out, be sure to paint lines to show the dimensions. Then situate the boards accordingly and lay them where they need to go.

Step 4: Level the Forms

The forms must be in the precise location that you need them since they cannot be adjusted once the concrete has been poured. Square up the corners of the forms and then make sure that they are level. Uneven forms will cause the concrete to be uneven. Use heavy duty framework that is firmly in place so that it can handle the weight of the poured concrete.

Step 5: Make the Concrete

Follow label instructions when mixing concrete. The general mixing directions are as follows:Pour dry cement mix into the wheelbarrow.Add water to the dry mix, stirring constantly.Mix thoroughly and make sure the consistency is chunky. Mixture that is too soupy will not set up properly.garage foundation

Step 6: Pour the Foundation

Pour the mixed concrete into the forms; try to make it as consistent of a pour as possible. Once you start pouring concrete, do not walk away and leave it set until the entire foundation is poured. Use a trowel to level it off and smooth it over. After the concrete is smooth, make grooves in it using the trowel if you need a non-slippery surface, otherwise, leave it smooth. Let the concrete set-up and cure. Remove the forms after 24 hours. To avoid cracking in the concrete, soak it with a hose, using a gentle spray, at least twice a day for a few days. Do not let rain beat down on freshly poured concrete as it will cause depressions in the concrete and the foundation to be uneven.This article about foundation construction for a garage is provided for educational purpose only. A garage foundation construction needs professional expertise to do it properly. So it is always better to do the work by a professional engineer or a company.

How To Reduce The Cost of Building a House | Some Basic Concepts

Economical design is one of the most desirable factor in residential building planning and design. Civil engineers and architects work hard for making connection between the desires and the costs allowed by the owner of a project. There are some basic concepts that can be used for making a residential building economical under general circumstances. Remind that, every construction project is different and many of the time an engineer have to work with his professional experience & technical skills. But it is always best to know some general considerations for economical design of residential building design for clear concept on this topic. Also you can check the article on how much gravel costs per ton.

Some General Concepts Used For Reducing The Cost of Building a House

Economical design for building a house depends largely on the surrounding factors. But for general concept some techniques that are commonly known are given below.

■ Square shape of structure is advantageous. 15-20% wall is saved in square structure than to a rectangular structure of same area.

■ For 2 storey building half of the rooms should be at ground floor and another half at the upper floor.

■  Because it is about 25% cheaper to build in the upper floor than to build in the ground floor.

■  Another reason is the rooms in the upper floor get more sunlight and fresh air than to the ground floor.

■ It is economical to make outer walls thicker than to the inner walls.Provide specialized professional workers for specific works.

■ Construction work of residential building should be started in due time without any delay.

■ Delay in starting the construction work will increase the total cost of the project.

■ Do not use unnecessary structural members for beautification in architectural design if economical allowance is not upto the mark.

■ Design should be done by good structural engineers and architects.

■ Though it may cost some extra money for designing with them but sometimes it can reduce overall cost drastically.

■ Building design layout should be such that it would be easy for the contractor and labors to understand and work through the project without any mess.

Braced Cut – Types and Uses of Braced Cut

_______________Braced Cut__________

Braced cuts are the excavations that arelaterally supported. The vertical side of the excavations are are supported by a sheeting and bracing system. It consists of relatively flexible sheeting placed against the excavation walls. The lateral thrust on the sheeting is resisted by the horizontal members in compression (struts) is known as bracing system. Main components of braced cuts are struts, wales, sheet piles or wooden board.Types of Braced CutPicture courtesy: Deep Excavation

_____________Uses of Braced Cut________

Braced cut is used for different purposes.It is used to resist the lateral pressure.It provides safety to the construction workIt enables deep excavation.

_____________Types of Braced Cut__________

There are mainly two types of braced cut that is generally used under normal circumstances.Sheet pileWooden boardSheet Pile:  Sheet piles are used for bracing.Wooden Pile: Wood or timber is used for bracing.

Difference Between Sheet Pile and Wooden Board Braced Cut

Some basic differences between sheet pile and wooden board braced cut are shown below.

Advantages of Sheet Pile

Sheet pile has so many advantages than other types of bracing. Its main advantage is that it can be reusedwhich makes sheet pile economical.It has more strength than other types.Sheet pile braced cuts can be used easily in deep excavation.It can be reused.Resistance to weathering action is high.It is overall more economic than other in the long run.