Superplasticized concrete is one that demonstrates increased fluidity without change in water content. It is prepared by vigorously stirring a superplasticizer with ready-mixed concrete to improve the workability. To fully exploit the benefits of superplasticized concrete-which include increased slump, recovery of slump loss, and reduced slump loss with time-the superplasticizer should be added just before the concrete is poured. This procedure, however, has some disadvantages when applied to the conventional liquid-type superplasticizer. For example, the dosage cannot be adequately controlled and special equipment, such as a track-mounted admixture tank and dispenser, is required. LEOPACK, a powdery superplasticizer packaged in an alkali-soluble paper, was developed as a solution to these challenges.
Normally, a superplasticizer is added at the latest convenient moment between when the agitator track arrives at the construction point and the concrete is discharged. Since LEOPACK is composed of the powdery superplasticizer and its paper pack-both of which are designed to dissolve in the alkaline contents of the agitator track when stirred at high speeds for 2 min-the whole pack can be easily and quickly cast through the hopper of the agitator. There is no need to open the pack and no additional equipment is required. Moreover, since the proper amount of powder has been packaged, no further measurement is needed. The slump of the concrete can be managed by the number of added packs, making the superplasticizer useable by even an inexperienced engineer. Moreover, the packaging is very compact and not much storage room is required. By having it ready on the construction site, concrete slump that results from transportation hiccups, hot weather, and setting time can be quickly recovered. LEOPACK is indeed the ideal response superplasticizer for overcoming onsite problems.
The main ingredient of LEOPACK is a polycarboxylic acid ester whose molecular structure has been modified to achieve the powdery form. It is manufactured by spray drying and is moisture-free, which enables it to increase the fluidity of concrete without changing the water content. The fluidity is maintained for a long period by means of the contained surfactants, which restrain slumping with time (see Fig2). LEOPACK can therefore be added to concrete to recover slump loss.
Since a superplasticizer is added to concrete that has already been optimally mixed, there has been concern about its affinity to other base admixtures. LEOPACK was therefore designed to be inert to a variety of air-entraining (AE) water-reducing agents (see Fig3), which increase quantitatively in the market with time. Hence, it can be used without concern about the base admixtures of the concrete.
|Examination item||Standard taype||Retard taype|
|LEOPACK G-100||Standard value||LEOPACK G-200||Standard value|
|Bleeding(cm3/cm2):Difference with nothing||0.06||≤0.1||0.02||≤0.2|
:Difference with nothig
|Initial||+45||-60 ∼ +90||+95||+60 ∼ +210|
|Final||+55||-60∼ +90||+90||-60∼ +90|
|Compressive strength ration (%)
:Compare to initial
|Drying shrinkage(%):Compare to initial||98||≤120||95||≤120|
|Freeze-thaw resistance(%):Compare to initial||87||≥60||77||≥60|
|Loss with time(15minutes)
:Difference with initial
|Air(%)||0.0||+1.0∼ -1.0||+0.2||+1.0∼ -1.0|
|Chloride ion content in concrete(kg/m3)||0.00||≤0.02||0.00||≤0.02|
|Alkali content in concrete(kg/m3)||0.02||≤0.30||0.03||≤0.30|
Examination report by Japan testing center for construction materials:No.05A0516(G-100),No.05A0517(G-200)
The slump of the concrete in the agitator should be checked to determine the amount of LEOPACK required. The standard number of required packs can be calculated using the following formula:
Number of required packs = 0.00010 × C × S × V × Ft/0.235
where C is the concrete content (kg/cm3), S is the increase in slump (cm), V is the volume of the concrete in the agitator (m3), and Ft is the temperature calibration factor (which is 1.2 for a concrete temperature of 10°C and 1.0 for 20°C).Moreover, a choice should be made between the standard type (G-100) and the retard type (G-200). When the temperature is 15°C or less, G-100 is recommended, whereas for temperatures above 15°C, G-200 is recommended.
The required number of LEOPACK packs should be cast into the drum of the agitator through the hopper. To facilitate blending with the concrete, the unopened packs should be cast into the inner part of the drum and the mixture stirred at a high speed for 2 min, by which time LEOPACK should be completely dissolved. It should be confirmed whether the targeted fluidity of the concrete has been achieved before it is poured as usual.
|Bulk specific gravity||0.5-0.6|
|Chloride ion content||≤0.05%|
As noted earlier, LEOPACK G Series comprises the standard type(G-100) and retard type (G-200). The powdery superplasticizer is made up of 40-80 μm particles and comes in an alkali-soluble paper pack. The weight of each pack is 235 g and 30 packs are contained in a cardboard box, which has a total weight of about 7 kg.
Once in direct contact with water, the LEOPACK powder is transformed into a lump, which is difficult to dissolve. It should therefore be stored in a plastic bag and not exposed to rain or any other kind of water.
Disclaimer: The information herein is subject to change without notice. The information presented herein is true and accurate to the best of our knowledge, but without any guarantee unless explicitly given. Since the condition of use is beyond our control, we disclaim any liability, including for patent infringement, incurred in connection with use of these products, data or suggestions. Buyers must determine for himself, by preliminary tests, or the suitability of these products for his purposes. Careful precautions are required in handling all chemical products. Please refer to our MSDS.