Lightweight Concrete

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Lightweight concrete can be defined as a type of concrete which includes an expanding agent in that it increases the volume of the mixture while giving additional qualities such as nailbility and lessened the dead weight. It is lighter than the conventional concrete. The use of lightweight concrete has been widely spread across countries such as USA, United Kingdom and Sweden. The main specialties of lightweight concrete are its low density and thermal conductivity. Its advantages are that there is a reduction of dead load, faster building rates in construction and lower haulage and handling costs. Lightweight concrete maintains its large voids and not forming laitance layers or cement films when placed on the wall. This research was based on the performance of aerated lightweight concrete. However, sufficient water cement ratio is vital to produce adequate cohesion between cement and water. Insufficient water can cause lack of cohesion between particles, thus loss in strength of concrete. Likewise too much water can cause cement to run off aggreagate to form laitance layers, subsequently weakens in strength. Therefore, this fundamental research report is prepared to show activities and progress of the lightweight concrete. Focused were on the performance of aerated lightweight concrete such as compressive strength tests, water absorption and density and supplementary tests and comparisons made with other types of lightweight concrete.

TYPES OF LIGHTWEIGHT CONCRETE

Lightweight concrete can be prepared either by injecting air in its composition or it can be achieved by omitting the finer sizes of the aggregate or even replacing them by a hollow, cellular or porous aggregate. Particularly, lightweight concrete can be categorized into three groups:
i) No-fines concrete
ii) Lightweight aggregate concrete
iii) Aerated/Foamed concrete

1) NO-FINES CONCRETE

No-fines concrete can be defined as a lightweight concrete composed of cement and fine aggregate. Uniformly distributed voids are formed throughout its mass. The main characteristics of this type of lightweight concrete is it maintains its large voids and not forming laitance layers or cement film when placed on the wall. Figure 2 shows one example of No-fines concrete.

FIGURE 2: No-fines Concrete [2]
No-fines concrete usually used for both load bearing and non-load bearing for external walls and partitions. The strength of no-fines concrete increases as the cement content is increased. However, it is sensitive to the water composition. Insufficient water can cause lack of cohesion between the particles and therefore, subsequent loss in strength of the concrete. Likewise too much water can cause cement film to run off the aggregate to form laitance layers, leaving the bulk of the concrete deficient in cement and thus weakens the strength.
2) LIGHTWEIGHT AGGREGATE CONCRETE

Porous lightweight aggregate of low specific gravity is used in this lightweight
concrete instead of ordinary concrete. The lightweight aggregate can be natural aggregate
such as pumice, scoria and all of those of volcanic origin and the artificial aggregate such
as expanded blast-furnace slag, vermiculite and clinker aggregate. The main characteristic of this lightweight aggregate is its high porosity which results in a low specific gravity [17]. The lightweight aggregate concrete can be divided into two types according to its application. One is partially compacted lightweight aggregate concrete and the other is the structural lightweight aggregate concrete. The partially compacted lightweight aggregate concrete is mainly used for two purposes that is for precast concrete blocks or panels and cast in-situ roofs and walls. The main requirement for this type of concrete is that it should have adequate strength and a low density to obtain the best thermal insulation and a low drying shrinkage to avoid cracking [2]. Structurally lightweight aggregate concrete is fully compacted similar to that of the normal reinforced concrete of dense aggregate. It can be used with steel reinforcement as to have a good bond between the steel and the concrete. The concrete should provide adequate protection against the corrosion of the steel. The shape and the texture of the aggregate particles and the coarse nature of the fine aggregate tend to produce harsh concrete mixes. Only the denser varieties of lightweight aggregate are suitable for use in structural concrete [2]. Figure 3 shows the feature of lightweight aggregate concrete.

 3) AERATED CONCRETE

Aerated concrete does not contain coarse aggregate, and can be regarded as an aerated mortar. Typically, aerated concrete is made by introducing air or other gas into a cement slurry and fine sand. In commercial practice, the sand is replaced by pulverizedfuel ash or other siliceous material, and lime maybe used instead of cement [2]. There are two methods to prepare the aerated concrete. The first method is to inject the gas into the mixing during its plastic condition by means of a chemical reaction. The second method, air is introduced either by mixing-in stable foam or by whipping-in air, using an air-entraining agent. The first method is usually used in precast concrete factories where the precast units are subsequently autoclaved in order to produce concrete with a reasonable high strength and low drying shrinkage. The second method is mainly used for in-situ concrete, suitable for insulation roof screeds or pipe lagging. Figure 4 shows the aerated concrete.

FIGURE 4: Aerated Concrete [3]
The differences between the types of lightweight concrete are very much related to its aggregate grading used in the mixes. Table 1 shows the types and grading of aggregate suitable for the different types of lightweight concrete.

 

TOPIC- LIGHTWEIGHT CONCRETE AND APPLICATION                         IN CONSTRUCTION INDUSTRY

 

  1. INTRODUCTION

Concrete is one of the most popular construction materials used since hundred years ago. Because of its flexibility in usage it becomes more important and is preferred compared to timber or steel. The combination of cement, coarse aggregate, fine aggregate and water makes up a concrete. It is an acceptable fact now that not only the strength of concrete which plays a main role, in deciding the quality of concrete but what matters most is the durability at services stage. This technological advancement forms a challenge to mankind to look into various ways and means to improve concrete.

Aggregate is one of the important ingredients in term of strength and bonding in concrete. In general, aggregate in concrete can be defined as those having apparent specific gravity of 2.4 or above. Aggregate can be divided further according to their particle shape such as rounded irregular, angular and flaky and according to their surface texture, i.e. glassy, smooth, granular rough, crystalline and honey, combed and porous. By virtue of the aggregate’s density, the concrete produce is quite heavy and has a density of about 2400kg/m³.

Reducing concrete density will lead to economical construction because it reduces the cost of transportation, handling and constructability. One of the ideas to make concrete lighter is by the introduction of lightweight aggregate and air entraining agent. Using lightweight aggregate and air entraining agent in the concrete results reduction of dead load, faster construction time and lower haulage and handling cost.

It is this true that the application of LWC (Lightweight concrete) is limited to certain purposes compared to normal concrete, but the introduction of LWC gives more alternative to construction industry, which currently focuses on natural resources. Some of the lightweight aggregate are manufactured from waste material such as Lytag, whereby it was produced from pulverized fuel ash (PFA). Study shows that in Malaysia the use of LWC is gaining popularity whereby in the 1994, more than 100,000m² of LWC panel have been produced and it can be said that the demand for the coming year will increase [MCB Concrete Product Sdn. Bhd, 1994].

Some of the major project where LWC panels had been used and proved beneficial areas follows:-

  1. Taman Rasah Jaya Single-storey link houses, Seremban. In this project, M-PANELS (LWC panel) is used as a wall element. The standard M-PANELS is 100mm wide with length available from 150mm, in 100mm increments.
  2. Terrace houses of Taman Puteri, Kulai, Johor.
  3. Housing project Desa May, Pulau Pinang.
  4. Venice Hill’s Condomonium, Cheras, Selangor.

The LWC panels produced for the above mentioned projects are able to withstand the industrial environment. This is evident of the capability of LWC in the construction industry. It is of paramount importance that research on LWC be extended and intensified to incorporate other durability test that normally done on normal concrete. By so doing the effectiveness of LWC can be compared to normal concrete.
1.1       ISSUE OF THE TOPIC / PROBLEMS STATEMENT

LWC (Lightweight Concrete) has been adopted all around the world for the last 2 decades. But, in Malaysia the use of LWC is not very common; this may be due to large amount of gravel aggregate still available in the market. Malaysia imports lightweight aggregates from France and Germany, and in 1983, lightweight wall panel factory was set up at Nilai, Negeri Sembilan.

Based on the statement, we know that the construction industry in Malaysia have a problem about the LWC application. May be it is not popular relating expensive cost, less knowledge and experience, not having enough the skill worker, the machinery and appliance to constructed the LWC is not enough, or other reasons.

 

1.2     OBJECTIVE OF THE STUDY

            1. To understand the Lightweight concrete and level of application in                         construction industry mainly Malaysia.
2. To compare the strength and density of LWC with normal concrete.
3. To know that the different types of LWC and application in              construction industry.

 

1.3   SCOPE AND LIMITATION OF THE STUDY

The main purpose of this research is to know what is the lightweight concrete and used level in construction industry at Malaysia. Any factor will be included in this research as a recommendation. This research methodology selected for this research is interview and get information from developer or local authorities, get information from oversea such as UK and other countries about the lightweight concrete and also from reference books so that related the lightweight concrete and application in construction industry at Malaysia.

Our study also using 3 sites to research about the lightweight concrete in Malaysia and choice the site at around Selangor state, it is because the Selangor state is develop state in Malaysia and attempt to develop the lightweight concrete in our country. It also suitable with Rancangan Malaysia ke-9 when the Malaysia government wants at each government          project must use the lightweight concrete although small amount. 

 

    1. METHODOLOGY OF THE STUDY

 

This stage involves the procedure of collecting data in order to achieve the objectives of this research. This stage can be divided into two categories: -

            1.4.1    Primary data:

            This is a process of obtaining main data for the research. The data                           and information are obtained by conducting interviews and getting                                 information with the developer and local authorities on the                                            lightweight concrete in Malaysia. The data will be collected through                        the appointment, ask questionnaire and comparison to find if they                           could be classified in order to give the best result of the research.

            1.4.2    Secondary data:

            These data will be obtained through reading and analyzing the                                information resources that related to the research topic.   

CONCLUSIONS
The initial findings have shown that the lightweight concrete has a desirable strength to be an alternative construction material for the industrialized building system. The strength of aerated lightweight concrete are low for lower density mixture. This resulted in the increment of voids throughout the sample caused by the foam. Thus the decrease in the compressive strength of the concrete. The foamed lightweight concrete is not suitable to be used as non-load bearing wall as the compressive strength is 27% less than recommended. Nevertheless the compressive strength is accepted to be produced as non-load bearing structure

 

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