A BRIEF COMPARISON OF PCE SUPERPLASTICIZER & SNF WATER REDUCING AGENT
SNF water reducing agent
SNF(Naphthalene based) water reducing agent is commonly referred to β-Naphthalene Sulphonate Formaldehyde Condensate (short name: SNF, PNS, NSF, etc…). It is the largest and most widely used water reducing agent in China currently(≥ 70%). It is characterized by high water reducing rate (15% - 25%), no air entrainment, little influence on setting time, relatively good adaptability with cement, composite use with other additives and relatively low price. SNF is widely used to prepare high fluidity, high strength and high performance concrete. The slump loss of concrete with simple addition of SNF is faster. In addition, the adaptability of SNF to some cement needs to be improved.
PCE superplasticizer
PCE superplasticizer plays an important role in high-performance concrete. With the development of concrete technology, more and more attention is paid to the durability of concrete. As the durability increases, the water-binder ratio of concrete often needs to be reduced, but the fluidity of concrete still needs to meet the requirements of pumping construction. In addition to the high water-reducing effect, the water-reducing agent also needs to be able to control the slump loss of concrete, and the ordinary high-range water reducing agent often fails to meet the requirements.
As a new generation of high-performance superplasticizer, the PCE has a comb-shaped molecular structure, it is featured as good adaptability with cement, low dosage, high water reducing rate, good slump resistance of the prepared concrete, good workability etc. Moreover, it overcome the shortcomings of SNF with formaldehyde in the production, especially suitable for the production of high performance concrete, has been widely researched and developed rapidly in recent years. While from the perspective of the variety and market share of PCE on the market currently, the application and promotion of PCE is still in its early stages, and it has promising application prospects.
In the experimental comparison of PCE superplasticizer and SNF water reducing agent, the performance characteristics of them are studied as below:
(1) The water-reducing rate of PCE is significantly higher than that of SNF water-reducing agent. When the same water-reducing rate is achieved, the dosage of PCE is much lower than that of SNF water-reducing agent.
(2) The slump retention of PCE is significantly better than that of SNF water-reducing agent. The high fluidity concrete prepared with PCE can still reach the pumping requirement after 1h;
(3) With the increase of dosage, the water reducing rate limit of the PCE is much higher than that of the SNF, and the SNF water-reducing agent has basically reached its limit when dosage is about 2.0%, which shows that the PCE is more suitable for preparing low water-cement ratio high-strength concrete.
The results show that, compared with the SNF water-reducing agent, the PCE superplasticizer has the characteristics of better cement adaptability, lower dosage, higher water-reducing rate, less slump loss of concrete through time, and it is more suitable for preparing low water-cement ratio concrete.
Concrete Mix Attributes,and Slumps
A concrete mix is like a chef’s good recipe. Concrete is composed of aggregates, Portland cement, water, and any other cementitious material or chemical admixture. Some concrete mixes will have entrapped air by using admixture or air-entraining cement. Concrete mixes could also have chemical components used to accelerate, retard or improve manageability, reducing in certain instances water quantities, increasing its strength or altering concrete properties. Selecting the best concrete mix is a task that has to consider costs and placement requirements while providing a great aesthetic and integral product.
Concrete Mix Key Attributes
A great concrete mix should consider:
1.Workability: The concrete mix workability is the property that determines the mix capacity to be placed and consolidate properly, allowing to finish a product without segregation.
2.Consistency: This property determines the mobility and slump of the concrete mix. This characteristic is measured in terms of slump, the higher slump values, the more manageable, and greater mobility will be obtained.
3.Strength: This is one of the most important characteristics of a concrete mix, and the most known property of concrete, it is measured using it compression resistance, after the concrete has reached 28 days after being poured.
4.Water-Cement Ratio: The W/C ratio on a concrete mix, is defined as the relationship and ratio between the weight of cement, the weight of water being added to the mix, plus added pozzolan. This characteristic has a direct and linear relationship with the mix strength.
5.Durability: A good concrete mix will provide you with concrete that could withstand severe weather conditions and changes without any decay sign. The more durable the concrete is, the more resistant to weather variations such as freezing, wetting, drying, and heating.
6.Density: Concrete mixes could also be specified for certain applications such as counterweights, radiation protection, insulation or endurance and resistance.
7.Heat Release: A concrete mix should also consider heat being released under a chemical reaction that will fade at a reasonable rate without producing cracks or shrinkage.
Concrete Mix: Recommended Slumps
When preparing a concrete mix, you must consider the type of slump being expected. Follow these recommended slumps:
Reinforced foundation walls and footings:
1.Maximum Slump 75mm
2.Minimum Slump 25mm
Plain footings, caissons, and substructure walls:
1.Maximum Slump 75mm
2.Minimum Slump 25mm
Beams and reinforced walls:
1.Maximum Slump 100mm
2.Minimum Slump 25mm
Building columns:
1.Maximum Slump 100mm
2.Minimum Slump 25mm
Pavements and slabs:
1.Maximum Slump 75mm
2.Minimum Slump 25 mm
Mass Concrete Mix:
1.Maximum Slump 75mm
2.Minimum Slump 25mm
Post time: Sep-19-2020