PRECAUTIONS BEFORE PLACING CONCRETE INSIDE COLD

PRECAUTIONS BEFORE PLACING CONCRETE 

INSIDE COLD

If we go for concrete work in general it is not a problem at all, but specially when cold weather comes on all of the sudden. To handle the cold, have everything you will need on hand and review the following pointers:

Frozen ground-NEVER place concrete upon frozen ground or onto snow or snow. First, frozen ground will settle when it thaws, cracking the concrete. Second, when the ground is wintry, the concrete in contact with it will likely be cold and will set much more slowly. You can even obtain crusting, with the top area of the concrete set and the bottom still soft.
If the ground is frozen, you can unfreeze it using hydronic heat pipe joints and blankets (such as those from Ground Heaters), or electrical blankets (check out Power Blanket).
Remove all snow and snow in areas where concrete shall be placed. Also remove any standing water which may get mixed into the real.

Warm up anything that will are in contact with the concrete, including forms in addition to any embedments, to at very least 32°F. If it's not too cold so you cover everything with tarps the morning before the pour, it will continue dry and warm enough. Keep tools within your truck or trailer.
Be all set with blankets, even if you do not think it will get in which cold. Also consider whether you should have lights if the concrete pieces more slowly than expected and also the winter sun sets just as you're finally wanting to start finishing.

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Pervious Concrete

Pervious Concrete

Pervious concrete  (also called porous concrete , permeable tangible, no fines concrete floor and porous pavement) could be a special type of concrete with a high porosity useful for concrete flatwork applications that permits water from precipitation and other sorts of sources to pass directly by using, thereby reducing the runoff for a site and making it possible for groundwater charge. Pervious concrete is made employing large aggregates with little in order to no fine aggregates. This concrete paste after that layers the aggregates and allows water to be able to feed the concrete floor slab. Pervious concrete is traditionally found in parking areas, areas with lighting site visitors, residential streets, pedestrian routes, and greenhouses. It is an important request for lasting construction and is one of the low impact advancement techniques as used by builders to protect water the best quality.

Construction

Pervious concrete consists regarding concrete, coarse aggregate and standard water with little to no great aggregates. The addition of almost no sand will enhance the toughness. The mixture carries a water-to-cement relation of 0. 28 to be able to 0. 40 with a void content of 15 to 25 %.

The correct variety of water inside the concrete is very important. A low water to cement ratio increase the potency in the concrete, but inadequate water might bring about surface failure. A proper water content provides the mixture a wet-metallic appearance. As this concrete floor is sensitive in order to water content, the mixture must be field checked. Entrained air could be measured by an instant Air system, where the concrete can always be stained black and sections are often analyzed under some sort of microscope.

A common flatwork variety has riser strips at the summit such that the screed could be 3/8-1/2 in. (9 to 12 mm) previously mentioned final pavement degree of lift. Mechanical screeds are better manual. The riser strip are removed to steer compaction. Immediately right after screeding, the concrete is compacted to boost the bond and smooth the counter. Excessive compaction of pervious concrete brings about higher compressive power, but cheaper porosity (and as a result lower permeability).

Joints are tooled with a rolling jointing tool prior in order to curing or saw cut soon after curing. Curing contains masking concrete with 6 mil. plastic-type sheeting within 20 moments regarding concrete discharge. However, this contributes to many waste sent to be able to landfills. Additionally, preconditioned absorptive lightweight aggregate in addition to internal curing admixture (ICA) are used to effectively cure pervious tangible without waste generation.

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Erosion of Concrete

Erosion of Concrete

Erosion is one way of wearing of concrete that is observed hold of flowing water. The water body that benefits erosion may carry solid particles that leads to serious erosion to cement.

Another term cavitation is closely related to erosion which will be discussed in the next write-up. Let’s concentrate to this subject matter. We are listing the factors that determine the amount of erosion:

a. Quantity in the transported particles

b. Shape of such particles

Almost damaged concrete channel by erosion
c. Size of such particles

d. Hardness of these kinds of particles

e. Velocity of particle mobility

f. Formation of eddies gary the gadget guy. At last quality of cement

The concrete quality, especially in surface zone is critical to resist erosion of cement. We will provide factors and approaches to control erosion in the extremely next post. Like abrasion the resistance against erosion is also related to the potency of concrete but mix composition of concrete is additionally vital.

Exposed reinforcement due to concrete erosion

Erosion is a mechanical damage of concrete that is frequently associated with corrosion. Marine concrete is the ideal example of such harm. With this corrosion effects, erosion is happened when mechanical damage to concrete is occurred by the waves of water with pea gravel and sand carried by them. Sometimes crystallized salt takes the portion of impacting from carried particles.

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Silica Fume

Silica Fume

Silica fume is a by-product from the silicon, ferrow-silicon producing process from quartz and carbon in electric furnace. It is such as extremely fine spherical particles. Before 1990 it turned out viewed as factory waste. But also in 1987, silica fume concrete was useful for Deepak Fertilisers. It was learned that it has beneficiary effect about concrete, including increase in strength and durability. Now nearly all major projects are applying High Performance Silica Fume concrete. Some of the important projects where silica fume can be used are Tehri Dam, Bandra Worli Seashore Link, Nuclear Power Station, Kaiga, Karwar, Mumbai to Poona express way. Replacing cement by 12. 5 per cent silica fume contains the maximum advantage in increasing the strength. As a result regarding increase in its demand, right now silica fume is expensive. However when analysed against the price tag on an alternative concrete of similar performance it's found to be economical in addition. This conclusion has been drawn on the cost analysis of Mumbai-Poona convey way.

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Recycling Crusher Dust Crusher

Recycling Crusher Dust Crusher

         Recycling where possible Crusher Dust Crusher dust could be the by-product of crushing of rock to get coarse aggregates/jelly for concrete. The disposal in this dust is a serious the environmental problem. If it is possible to use this crusher dust in manufacturing of concrete and mortar through partial or full replacement connected with natural sand, then this will not only save the money necessary for construction but while doing so it will solve the problem of disposal on the crushed dust. The researchers have reported that replacement of natural sand along with crusher dust results into reduction in workability and this can be compensated by using chemical admixtures.

The particular test results reveal:
1. Replacement of natural sand by crusher dust just isn't detrimental upto 50%.
2. Concrete with 100% crusher dust can be used with greater precaution. In such concrete durability requirement just isn't met in stipulated 28 days. However, incorporating fly ash can boost the durability characteristics.
3. Combination of crusher dust and fly ash is beneficial in cost and durability facets.

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GOOD CONCRETE PRACTICES – TIPS

GOOD CONCRETE PRACTICES – TIPS 

Concrete is a mixture of cement , sand , aggregates , water and admixtures  For making good concrete certain practices needs to be followed .
Those practices can be summarised as follows:

1. Quality of incoming materials : 

Check the following : 
a. Cement Test certificate  : Parameters of cement like compressive strength , setting time , fineness etc
b. Sand : Silt content & Sieve analysis
c. Coarse aggregates : Sieve Analysis
d. Chemical Admixtures : Solid content ; Base of the admixture – whther naphthalene, melaimine or PC based

2. Availability of Mixers 
It is advisable to do mixing using concrete mixers.  Hand mixing will produce non uniformity in quality of concrete

3. Transportation of concrete 
It is advisable to use concrete as quickly as possible . A delay in using concrete can lead to quality issues .
Therefore plan for transportation of concrete in the quickest possible time using wheelbarrows, transit mixers etc

4. Use cover blocks for concrete structures for durability

5. Check the slump of concrete using a slump cone

6. Avoid using excess water in the concrete mix. Excess Water could lead to lower compressive strength and increase in cracks

7. Use vibrators for better compaction of concrete : Use needle vibrators for better compaction and to remove air voids

8. Make available the finishing equipments for better finish
9. Curing should be done for a minimum of 10 days for enabling the concrete to achieve high compressive strength and durability

10. Formwork / shutters should not be removed very quickly : Vertical formwork to columns can be removed within 16-24 hours; Props to slabs spanning  upto 4.5 m should be removed within 7 days , beyond 4.5 m props to be removed within 14 days ; Props to beams and arches for span upto 6 m can be removed within 14 days , props spanning over 6 m can be removed within 21 day

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