POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH

CC 203:CONCRETE TECHNOLOGY

ASSIGNMENT 1 (TOPIC 1 & 2)

NAMA AHLI KUMPULAN:

NAMA NO MATRIK

NORSYADIQAH BT SUHAIMI08DKA10F1091

ASIAH BT ISMAIL08DKA10F1089

NURUL FARADILLA BT J NASRUL

08DKA10F1065

NURSAKMAWANI BT ABD RAFAR

08DKA10F1068

CONTENTS

NO TITTLE PAGES1 INTRODUCTION

2 QUESTION 1

3 QUESTION 2

4 QUESTION 3

5 QUESTION 4

6 CONCLUSION

7 ATTACHEMENTS

8 REFERENCE

INTRODUCTION

QUESTION 1

explain different types of mixture

QUESTION 2 EXPLAIN AND DIFFERENTIATE THE TYPES OF ADDITIVE:

RETARDING SUBSTANCES are known to delay hydration of cement without affecting the long-term mechanical properties. They are used in concrete to offset the effect of high temperatures, which decrease setting times, or to avoid complications when unavoidable delays between mixing and placing occur

WATER DECREASING SUBSTANCESThese reduce the amount of water needed in the concrete mix.

RETARDING SUBSTANCES WATER DECREASING SUBSTANCES

Extending concrete initial setting time for

proper finishing without cold joint during hot

weather.

can be used to increase set time in hot weather, similar to retarding admixtures, but their main role is to allow for a more fluid mix with a lower water content. 

Increasing the workable time of concrete up

to several hours.

Commonly, 5% to 10% less water may be used in the mixture when water-reducing admixtures are utilized.

Providing flexibility in planning and scheduling of concrete pours

The less water (lower water/cement ratio) used to achieve a workable mix will result in a higher strength concrete.

.Applicable for massive concrete, cast

concrete and large area construction.

There are low, mid, and high range water reducers available that will lower the amount of water needed by 5% - 30%. Most concrete producers add a small percentage of water reducer to all the concrete they batch these days.

QUESTION 3

WITH THE AID OF DIAGRAM,SHOW THE METHOD OF COMPACTING CONCRETE

Vibration:

To compact concrete you apply energy to it so that the mix becomes more fluid. Air trapped in it can then rise to the top and escape. As a result, the concrete becomes consolidated, and you are left with a good dense material that will, after proper curing, develop its full strength and durability.

Vibration is the next and quickest method of supplying the energy. Manual techniques such as rodding are only suitable for smaller projects. Various types of vibrator are available for use on site.

Poker Vibrators

The poker, or immersion, vibrator is the most popular of the appliances used for compacting concrete. This is because it works directly in the concrete and can be moved around easily.

Sizes:

Pokers with diameters ranging from 25 to 75mm are readily available, and these are suitable for most reinforced concrete work. Larger pokers are available - with diameters up to 150mm - but these are for mass concrete in heavy civil engineering.

Radius of action:

When a poker vibrator is operating, it will be effective over a circle centred on the poker. The distance from the poker to the edge of the circle is known as the radius of action.

However, the actual effectiveness of any poker depends on the workability of the concrete and the characteristics of the vibrator itself. As a general rule, the bigger the poker and the higher its amplitude, the greater will be the radius of action. It is better to judge from your own observations, as work proceeds on site, the effective radius of the poker you are operating on the concrete you are compacting.

The length of time it takes for a poker vibrator to compact concrete fully depends on:

1. The workability of the concrete: the less workable the mix, the longer it must be vibrated.

2. The energy put in by the vibrator: bigger vibrators do the job faster.3. The depth of the concrete: thick sections take longer.

question 4

a)List down THREE (3) method curing of concrete

1-Water curing.

immersion ponding spraying or fogging wet covering

2-Membrane curing.

concrete could be covered with membrane which will effectively seal off the evaporation of water from concrete.

3-Application of heat

Steam curing at ordinary pressure Steam curing at high pressure Curing by Infra-red radiation Electrical curing.

4-Miscellaneous Methods of Curing.

Calcium chloride is used either as a surface coating or as an admixture.

b)With the aid of diagram,explain the procedures of curing concrete.Leave the form work used to create the concrete formation. The form work itself, if left in place, or on the underneath of a suspended slab, or around a concrete column will stop theconcrete drying out too quickly, and so can be said to be a curing agent.

curing a concrete house slab by ponding

Use ponding, which as illustrated in the photo above, is done by forming a dam wall of sand around the concrete formation and then flooding with water. This method has the following disadvantages:

It takes a fair bit of work to do, and then quite often a breach occurs and the water runs off the slab.

Usually this can only be done for a few days as it inhibits other work and the pressure is usually on to get the walls up.

A possible drawback of this method, especially if soil or clay is used, is the chance of staining the concrete.Spray water onto the formation. A simpler way is to just keep water sprayed onto the slab with garden sprinklers or hand held hose pipes. Following are some disadvantages that you need to consider if you intend to use this method:

This method is very wasteful of water Again, it can only be done for a short period usually. If you hand water, it should be wet all

the time, that is you should not let it dry out at all, almost impossible to do.

Use some sort of cover that holds and retains sprayed on water, like a sand layer or hessian. The sand cover or hessian has to be kept wet and if they do dry out they actually aid in sucking moisture out of the concrete.Use a plastic shield, which basically is a plastic sheet laid on top of the slab to stop the evaporation process. This is one of the most efficient methods of curing concrete. Usually a spray from a hose pipe is used to wet the surface and the plastic is laid on, with generous laps at the joints. Use timber or cement blocks to keep the plastic in position, rather than taping the joints. To a certain extent the plastic can be used a few times. A major benefit of plastic is that it does not stop other work, like building the walls, and so it can be left in position for weeks if need be.The photo shows concrete columns that have had the form work stripped (for further use) and then wrapped in a clear plastic film. The evaporation from the concrete condenses on the inside of the plastic and the surface of the column remains moist.

plastic wrapped around aconcrete column

Use concrete curing oils or curing compounds. These compounds and oils now come in a variety of types. Used the water soluble waxy emulsions that can be sprayed onto the freshconcrete with a hand pump type spray. They are milky white when used but dry into a clear waxy film. They have the advantage that that they can be sprayed onto footpaths and the like even before the concrete is set enough to walk upon. Another major use is on concrete walls. They remain on the surface for weeks and finally break down in sunlight.

Be hesitant to use concrete curing oils on internal floors, on the off chance that any residue would stop the full adhesion of ceramic tile glues etc.

Other types of concrete curing compounds are PVA based, chlorinated-rubber or resin based. They can also be obtained In coloured versions that fade over time.

conclusion

Firstly we want to thank you to our lecturer,Puan Nor Hayati bt Palil for her guidance.