The Influence of Super Plasticizer on Concrete, Made With Portland Cement

ABSTRACT

The rate of strength development of concrete depends  mainly  on  cement  types, water cement  ratio, and  sometimes  the  use  of  admixtures  in this  case  super plasticizer. Super plasticizers  are indispensable  in  modern  concrete, it provides  high  workable  concrete  at  low  water  to  cement  ratios  and  resulting  in  the  production  of  high  strength, durable  and  sustainable  concrete.

However, the  issues of cement –Sp’s  incompatibility   ,when  wrong  combination  is  used, have  been  identified  by  researches. This  research  Therefore   is  aimed  at  accessing  the  influence  of  super plasticizer  on  concrete,  made  with  Portland  cement.

Concrete  is  a  composite  material  water  with  cement, aggregates   water comprises  in  quality  the  largest  of  all  man-made  materials although  aggregates  make  up  three  fourth of  the  volume  of  concrete  the constituent   of  concrete  is  cement  paste.  Super plasticizer

in  concrete  confer  some  beneficial  effects  such  as  acceleration, retardation,  air  entrainment  water  reduction,  plasticity  etc.  and  these  effects  are  due  to  their  action  on  cement. The provides satisfactory performance under aggregate environments Strength of modified.

Concrete is compare with the normal concrete i.e. without super plasticizer. The  results  after the research  experiments  carried  out  shows  the  significant  enforcement  in the strength  and workability  of modified   concrete. Workability of concrete  Mix design of concrete using admixture super plasticizer.

Chapter 1

Introduction

1:1     Background of study

Concrete is a composite material made out of water, aggregates on ensconce in a hard matrix of materials that fills the space between the aggregate particles and plus them together. The mixing water induces hydration process in concrete production. (Which is responsible for strength development) and assist in workability. The hard matrix of material that glues the aggregate particles (sand and Gaul etc.) is Ordinary Portland Cement (OPC). In order to perform its intended functions, concrete is made with different types of cement and in this case, contains admixture (super plasticizer).

Portland cement is the name given to a cement obtained by initially mixing together calcareous and argillaceous, or other silica, alumina and iron oxide-bearing materials, baring them at a clinkering temperature and grinding the resulting clinker. Ordinary Portland composes of Belite (c2s) celite (c3A), Felite (c4AF) and gypsum  which are responsible for early  cement strength, strength  development  at 28 days, setting  time  and  heat of  hydration and cement  coloration  respectively. The gypsum added during grinding of clinker adjusts seating time and improves cement soundness.

Qualities of cement may differ based on the production origin.

In the early 1960’s, a super plasticizer was invented in Japan. By the inclusion of the super plasticizer ;high strength concrete  could be realized by reducing  w/c  to  fewer  than 30%  .The high strength concrete  was however.  Applied only to the factory products because it had a large loss in slump. Super plasticizer has led to the cost – in place high – strength concretes with good workability. More strength and higher durability.

Super plasticizer is a type of water reducers, however the difference between super plasticizers and water reducer is that sp will significantly reduce the water required for concrete mixing.

There are few advantages obtained when sp is used

1. Produce high workability concrete with constant cement content and strength with objectives for easy placing and compaction, produce concrete with normal workability but lower water requirement; production of concrete with combination of high workability and low water content.

This study have been done on impact of sp on fresh and hardened concrete. It was generally observed that with a very low water/ cement ratio sps significantly influence concrete mixture fluidity. The reduction of water cement ratio. Improves the durability of concrete. Depending on the concentration of the sp on the fresh concrete which will determine their effect on workability and strength of the concrete being the paired. Thus, the effectiveness of a given dosage rarely depends on the water/ cement ratio. And although increment in dosage will enhance the comprehensive strength but when the dosage goes beyond the specified limit, the comprehensive strength will only get reduced.

1.2   Statement of Research Problem                                                                          

In the world, about 90-95 percent of the construction materials market for both structural and non-structural applications is made of concrete compared with other materials used for similar functions. Concrete, generally, is a product made from cement, water and aggregates and an additional material known as admixture, is sometimes added to modify certain properties of concrete. Cement is the chemically active constituent but its reactivity is only brought into effect upon mixing with water. The aggregate plays no important roles in chemical reaction but its usefulness arises because it is an economical filler material or hard composite material with good resistance to volume changes which take place within the concrete after mixing,  besides improving durability of concrete.

In hardened state, concrete is a rock like material with a high compressive strength. In its plastic state, concrete may be molded into any form of shapes, it may be used to advantages architecturally or solely for decorative purposes. Concrete has low tensile strength, and hence, this is the reason why it is used with steel bar to resist any tensile forces in the reinforced concrete. However, concrete is usually used in building for foundations, columns, beams and slabs, in shell structures, bridges, sewerage treatment plants, roads, cooling towers, railway sleepers and so on. In precast concrete industry, concrete is widely used as concrete blocks, cladding panels, pipes, piles and lamp posts (1).

Nowadays, more than 70% of in-situ concrete in the world is produced by the ready mixed concrete industry. The ready mixed concrete producers are using a super plasticizer (SP) admixture which is readily available from various manufacturers. Super plasticizer (SP) is used to increase the workability without changing the water/ cement ratio. Or, it  Journal of Agricultural Science and Engineering Vol. 1, No. 2, 2015, pp. 70-74, 71 can be used to increase the ultimate strength of concrete by reducing water content while maintaining adequate workability. Super plasticizer is a type of water reducers; however, the difference between super plasticizer and water reducer is that super plasticizer will significantly reduce the water required for concrete mixing (2).  Generally, there are four main categories of super plasticizer: sulfonated melamine- formaldehyde condensates, sulfonated naphthalene- formaldehyde condenses, modified lignosulfonates and others such as sulfonic- acid esters and carbohydrate esters. Effects of super plasticizer are obvious, i.e. to produce concrete with a very high workability or concrete with a very high strength. Mechanism of super plasticizer is through giving the cement particles highly negative charge so that they repel each other due to the same electrostatic charge. By deflocculating the cement particles, more water is provided for concrete mixing (2). For general usage, dosage of super plasticizer is between 1- 3 l/m3.  However, the dosage can be increased to as high as 5- 20 l/m3. Since concentration of super plasticizer is different, any comparison of performance should be made on the basis of the amount of solids, and not on the total mass. Effectiveness of a given dosage of super plasticizer depends on the water/cement ratio. Effectiveness increases when w/c decreases. Compatibility with actual cement is one of the most important parameters that needed to be considered, and it is not recommended that the cement and super plasticizer conform the standard separately (2).

There are few advantages obtained when super plasticizer is used: produce high workability concrete with constant cement content and strength, with objective for easy placing and compaction; produce concrete with normal workability, but lower water requirement; production of concrete with combination of high workability and low water content; and designing a normal strength and workability concrete with less cement content (3). Usage of super plasticizer becomes famous nowadays since it possesses advantages for both fresh and hardened concrete. The utilization of super plasticizer will have positive effects on properties of concrete, both in the fresh and hardened states (4). In the fresh state, utilization of super plasticizer will normally reduce tendency to bleeding due to the reduction in water/ cement ratio or water content of concrete. However, if water/ cement ratio is maintained, there is tendency that super plasticizer will prolong the time of set of concrete as more water is available to lubricate the mix. In the case of hardened concrete the use of super plasticizer will increase compressive strength by enhancing the effectiveness of compaction to produce denser concrete. Risk of drying shrinkage will be reduced by retaining the concrete in liquid state for longer period of time. In addition, rate of carbonation become slower when water/ cement ratio is decreased with the presence of super plasticizer (4). Different types of super plasticizer will normally have different effects on properties and performance of concrete. (5) Carried out an investigation to study the effect of two types of super plasticizers- acrylic polymer (AP) and sulfonated naphthalene (SN) on concrete containing high volume of fly ash. From the investigation, they concluded that AP- based super plasticizer performs significantly better than the SN- based super plasticizer, where it provides higher slump level, lower slump loss and higher water reduction. In addition, concrete containing AP- based super plasticizer gives higher compressive strength and durability performance (in terms of CO2 and chloride penetration). Hence, addition of AP- based super plasticizer not only improves the slump loss problem of the concrete, but also it does not cause any reduction in the early strength development of hardened concrete. However, the influence of a super plasticizer by the name of (Mighty 2000) in addition,  they confirmed that slump of fresh concrete can be optionally controlled in all mix- designs if reactive polymer is added. Since workability of low water/cement ratio concrete is difficult to control, addition of reactive polymer can usefully maintain the initial slump of ready mixed concrete (6). In addition, they claimed that super plasticizer can really produce a good quality concrete by increasing the density of concrete, through significant reduction in water requirement and slump loss.

The reason for this research with the usage of super plasticizer is that it is able to impart considerable physical and economic benefits with respect to concrete. However, usage of admixture is not remedy for poor quality of concrete due to the use of incorrect mix proportion, poor workmanship in concrete mixing and the problems caused by low quality raw materials selection.

1:3 Objectives of study

1. To investigate the effect of sp on the fresh and hardened properties of concrete.
2. To determine the effect of sp on cement saving
3. To evaluate the durability properties of concrete reduced.
4. To learn the developments in materials production method and mechanical properties and their uses.
5. To study the function of super plasticizer
6. To achieve a concrete mix of strength greater than 35MPA

1:4 Significant of study

With the increase in the demand for larger structures that can with stand heavier load, the strength of the concrete has to be increased in order to meet the demands. Increased strength requirements of the concrete will require concrete of lesser water cement ratio (how workable mixes) Thus, methods of increased workability without reducing the strength and quality have to be explored in order to meet the demand. This research will focus specifically on the mixture super plasticizer. If the research is successfully completed, the results of this work would therefore assist in ensuring that building and construction sector is moved towards a better performance internals of sustainability and workability of concrete mix.

1:5 Scopes of study                                                                   

          This project is to study.

• Target commission steepen conclude at 7, 14, 21 days using grade m35 concrete grade, 42.5 Portland cement.
• Slump required at 100mm
• Specific gravity for grand stone and fine aggregate rammed bulk density for grand stone and fine aggregate, the size of aggregate falls in grand range of 14.6mm to 5.25mm, and that of fine aggregate ranging from 3.55mm to 0.06mm

Admixture to be used complete sp 430 as super Plasticizer

1:6 Limitations

Compressive strength is the most important property of concrete at hardened stage. Thus this research is focused on compressive strength of concretes made with the selected materials for accessing the cement-sp compatibility.

Pages:  67

Category: Project

Format:  Word & PDF

Chapters: 1-5

Material contains Table of Content, Abstract and References