Effect of Superplasticizers to Enhance the Properties of Concrete

SALAHALDEIN ALSADEY1, ABDELNASER OMRAN2

1Faculty of Engineering, Bani Waleed University, Bani Walid City, LIBYA

2Faculty of Engineering Sciences, Bright Star University, El-Breqa City, LIBYA

Abstract: This study aimed to study the effects of asuperplasticizing admixture, namely, Sikament-

NN superplasticizer, on concrete properties, such as workability and compressive strength.

workability and compressive strength. The experiment program included tests on workability,

slump test, and flow table. For hardened concrete’s compressive strength test, we compared the

properties of superplasticizer-based concrete with those of concrete without superplasticizer. The

superplasticizer led to a significant water reduction but maintained workability.

Keywords: Superplasticizer, compressive strength, slump, workability, admixture.

Received: June 7, 2021. Revised: January 12, 2022. Accepted: February 10, 2022. Published: March 23, 2022.

admixtures, but it is an engineered material

with several new constituents. Admixtures are

defined as materials other than cement, water,

and aggregates that are used as an ingredient

of concrete and added to the batch

immediately before or during mixing.

Admixtures are classified into two types:

mineral and chemical admixtures. Water-

reducing admixtures are chemical admixtures

that provide a wide advantage for concrete in

to cementitious materials (w/cm) used in the

mixture. By reducing the amount of water, the

cement paste will have high density, which

of concrete while retaining the flowing

properties of a concrete mixture. The use of a

superplasticizer will have positive effects on

the properties of concrete both in the fresh

and hardened states. In the fresh state, use of a

superplasticizer can reduce bleeding due to

the reduction in water–cement ratio or water

content of concrete. If the water–cement ratio

is maintained, then a superplasticizer can

extend the setting time of concrete as more

when the water–cement ratio is decreased

with the presence of a superplasticizer [1].

The slump of fresh concrete can be optimally

controlled in all mix designs if reactive

concrete by increasing the density of concrete

through a significant reduction in water

requirement and slump loss [2]. Water-

reducing admixtures (superplasticizers) are

generally used in concrete to increase strength

with low water–cement ratios [3, 4].

However, the admixture dosage should be

determined in the laboratory prior to its

application as its excess might result in a

slight improvement or adverse effects on the

workmanship in concrete mixing, and

problems caused by low-quality raw

materials. Superplasticizers are used to

increase workability without changing the

water–cement ratio or increase the ultimate

strength of concrete by reducing the water

content while maintaining adequate

workability. This work was carried out to

study the effect of superplasticizer dosage on

the properties of concrete with reducing

admixture and investigative the effects of

different dosages of Sikament-NN-based

superplasticizing admixture on workability

and strength of concrete.

2.1 Materials Used and Properties

The materials used in this study were cement,

fine, coarse aggregates, and water. A

experiment.

2.1.1 Ordinary Portland cement

Ordinary Portland cement (50 kg) was used

for the entire investigation. The cement used

in this study was a product from A Zlitan

Cement Industries, Libya, where it is widely

used in general construction such as in

buildings, bridges, and other precast concrete

products. Ordinary Portland cement Type-I

2.1.2 Fine and Coarse Aggregates

are used in concrete, namely,fine and coarse

aggregates. Many parameters need to be

considered in the selection of aggregates, such

as types of aggregate, size and shape of

particles, and strength of aggregates. All

aggregates must be free from dust as dust may

affect the bond between the aggregate and

cement particles. Locally available sea sand

was passed through a sieve of 6mm and used

as fine aggregate in this study. By contrast,

Water is important to ensure continuous

hydration. Tap water was used for mixing and

curing of concrete. Water must be free from

reactive elements such as reactive ions and

impurities to guarantee the quality of

concrete.

The superplasticizer used in this study was

To analyze performance, three design mixes

of concrete with different water–cement ratios

of 0.50, 0.55, and 0.60 and three

superplasticizer dosages of 0.8%, 1%, and

1.2% of cement content required for mix of

normal concrete were prepared. These mixes

abbreviated in Tables 4 and 5 for further

discussion and interpretation with respect to

normal concrete.

3. Results and Discussions

with and without superplasticizer.

3.1 Effect of Superplasticizer with Reduced

The results for slump and flow of

superplasticizer concrete are shown in Table

4. The data show the relation between dosages

of superplasticizer and slump and flow. The

values of slump and flow for different

superplasticizer dosages were then plotted as

not yield the true expected and desired slump.

The superplasticizer significantly increased

the workability of concrete due to

deflocculation and adsorption of highly

negative charges on cement particles. Before

adding the superplasticizer, the concrete was

less cohesive and presented a small diameter

(less than 500mm). According to BS 1881:

Part 105: 1984, concrete can only be

considered uniform and cohesive when it

Table 4. Workability Obtained for various ratios during the experiment

Water–Cement Ratio on Compressive

values of compressive strength for different

superplasticizer dosages were plotted as a

graph in Figure 3. The graph of compressive

strength versus water–cement ratio of

concrete revealed that the compressive

strength of the chemical admixture increased

with reducing water–cement ratio compared

with that of the control mix. In terms of the

influenceof the admixturedosage, the

superplasticizer presented different effects on

process was accelerated by the additional

water from deflocculation of cement particles.

Hence, increase in dosage could increase the

reduced the compressive strength. This

phenomenon occurred because overdosage of

superplasticizer could cause bleeding and

segregation, thereby affecting the

cohessiveness and uniformity of concrete.

Therefore, compressive strength

decreasedwhenthe used dosage exceeded the

optimum dosage. The optimum dosage of

superplasticizer was based on the highest

ultimate strength at 28 days. The graph

dosages with small intervals should be

investigated for a curve with the best fit.

Table 5.Compressive strength and Density

Determination of Slump, 1983, BSI, London,

1881.

[10] British Standard Institution, BS 1881: