LITERATURE REVIEWa. General Information About Lightweight Concrete Concrete, which haslower unit weight than 2000 kg/m3, are called lightweight concreteand it has less thermal conductivity than the normal concrete. They havedifferent properties than normal concrete. Therefore, when the insulation orlightness is desired in construction, lightweight concrete becomes the ultimatesolution. Lightweight concrete is separated into the three different categorieswith respect to their basic physical characteristic. First one is structurallightweight concrete, which has unit weight between 1120 and 1900 kg/m3.It must also have at least 17 MPa compressive strength.
That kind oflightweight concrete can be used in load carrying structural elements such ascolumns, beams or retaining walls. Second type of lightweight concrete iscalled “moderate strength concrete”. Its unit weight is between 2000 and 800kg/m3 and compressive strength is usually between 3.4 and 17 MPa.Moderate strength concrete can be used for building walls, roofs and floors orproduction of the masonry block. The last lightweight concrete type accordingto its physical properties is low-density lightweight concrete. This type ofconcrete has unit weight smaller than 800 kg/m3 and compressivestrength below from 3.4 MPa.
This low density concretes can be used for the”non-structural fills” or for some insulation purposes since it has much lowercompressive strength. (Bogas& Cunha, 2017)Figure: Westpac TrustStadium in New Zealand made by lightweight concrete In order to decreaseunit weight of the concrete, pores in the concrete must be increased. There aremainly three methods to increase pores in the concrete; using porous aggregate,using only coarse aggregate and creating a void in the paste. Using porousaggregate in the concrete instead of the normal weight concrete is the mosteffective method to decrease unit weight of the concrete because 60-70 percentof concrete’s volume is covered by aggregates. The concretes produced with thismethod is called lightweight aggregate concrete. The other method is makingconcrete with only normal weight coarse aggregate and cement paste.
Not using fine aggregate causes to have voidin the concrete and decreases the weight of concrete up to three tenths. Thisconcrete type could be used when the permeability is relevant. The final methodcreating porous in the paste which can be done with using prepared foam orgenerating gas in the cement paste. Concretes made by with this method calledcellular concrete. (Bogas& Cunha, 2017)b. Foam ConcreteFoam concrete is a type oflightweight and cellular concrete. It is produced with generating a void in acement paste with admixtures.
Foam concrete has become very popular in recentyears however it has a quite long history. The first foam concrete that madewith Portland cement is discovered by Axel Ericsson in early times of 1920s.Cement, water, sand and foam agent are the main components of the foamconcrete.(Thakrele,2014) While mixing the concrete, firstlyfoam agent and water are mixed together in the foam generator to produce foam thenthe freshly produced foam and cement paste are blended together. Sand or othernecessary admixtures can be added to the mixture. In the mixture, foam agent isthe significantly important because it is the source of air bubbles that causesto have lower density on the concrete.
Foam agents are generally protein orsynthetic based. Protein based foam agents causes a lot of small bubbleshowever synthetic based foam agents causes few but bigger bubbles because ofthat, protein foam agents causes better compressive strength on the concretecompared to the synthetic ones.(Amran,Farzadnia, & Ali, 2015) Unit weight of foam concrete variesbetween 240 and 1900 kg/m3 and its compressive strength values havealso wide range which is between 0.
48 and 43 MPa. Also studied showed thatmodulus of elasticity of the foam concrete is changes from 1.0 to 8.0 kN/mm2.
(Ramamurthy,Kunhanandan Nambiar, & Indu Siva Ranjani, 2009). According to Sircontec that producercompany of lightweight concrete in USA, price of foam concrete per m3is between 62.7 and 91.0 Turkish liras. Unit prices of cement and foam agent isupdated with the current values in Turkey. (Table 1) Table 1: Foam concrete mix proportionand price for 1 m3 Dry Density (kg/m3) Cement (kg/m3) Water for Cement (kg/m3) Foam (l/m3) Water for Foam (kg/m3) Foam Agent (kg/m3) Price (TL/m3) 300 250 140 780 45 1.77 62.
7 350 275 155 757 44 1.72 66.7 400 300 165 739 43 1.
68 70.8 450 340 185 706 41 1.6 77.
2 500 380 205 673 39 1.53 83.7 550 420 225 640 37 1.54 91 c. Pumice ConcretePumice is a volcanic lightweightaggregate which has voids in its structure.
That voids sourced from combiningof outflow gases and magma. The reason of having lightweight is that porousstructure. Pumice is the first used lightweight aggregate in the history andnowadays it is widely used to have lightweight concrete in the world. (Parhizkar,Najimi, & Pourkhorshidi, 2012) (AnwarHossain, 2004) Pumice aggregate’s most important constituents are of SiO2 andAl2O3. In order to produce the aggregates crushing andblasting process are not applied unlike normal aggregates, only gradation andwashing operations are applied. The process to creating concrete with pumiceaggregate is not different than the concrete with normal weight aggregate.
Accordingto study that is done by L. Gündüz, lightweight concrete with pumice aggregatehas air dry unit weight between about 1000 – 1300 kg/m3 andcompressive strength values are varies between 1.97 and 11.48 MPa. Modulus ofelasticity of the lightweight concrete with pumice aggregate is changes from1.
6 and 10 GPa. Moreover, in the same study, price of pumice aggregate concreteper 1 m3 is varies from about 20 to 50 Turkish Liras for the concretethat air dry unit weights between 1052 and 1272 kg/m3. (Table 2) (Gündüz& U?ur, 2005) The unit prices of pumice aggregateand cement are updated according to current values in Turkey.
Table 2: Mix proportion and cost ofpumice aggregate concrete Air Dry Density (kg/m3) Cement (kg/m3) Water (kg/m3) Aggregate (kg/m3) Price (TL/m3) 1272 180 158 1080 48.6 1245 137 161 1096 41.1 1216 110 163 1096 36.24 1156 72 165 1072 29.04 1104 52 167 1040 24.96 1052 40 170 1000 22.2 988 32 172 945 19.935 d.
Expanded Perlite Concrete Perlite is a kind of volcanic glassthat is formed from obsidian. It is quite dense material and contains about 3%water in it and density of perlite is about 1050 kg/m3. However, whenperlite heated up to about 1000 °C, the water in it vaporizes suddenly whichcauses expanding on perlite.
It became almost twenty times bigger than itsoriginal size. As a result of this process, expanded perlite’s loose weightdensity is about 35-45 kg/m3. Therefore, it became verydistinguishing material for construction industry. It is used in masonry andplastering process for insulation, fire resisting and reducing the noisetransfer purposes. It is also used for the creating lightweight aggregateconcrete. The mixing process is same as the normal concrete except airentraining admixture because the expanded perlite has very low density, mixingwith water is very difficult.
Hence, admixtures are used for this purpose.According to experimental study, expanded perlite light weight concrete have airdry density between 560 and 1710 kg/m3. The compressive strengthvalues vary between 3.4 and 30.0 MPa at 28-day.
(Jedidi,Benjeddou, & Soussi, 2015) Unit price of lightweight concretemade by expanded perlite is between 93.1 and 98.6 Turkish Liras with currentunit price of the materials in Turkey. (Table 3) (Jedidiet al., 2015) Table 3: Mix proportion of EPAconcrete and unit cost Air Dry Density (kg/m3) Cement (kg/m3) Water (kg/m3) Sand (kg/m3) EPA (l/m3) Price (TL/m3) 1867 300 210 1207 150 98.624 1245 300 210 994 300 97.
808 1216 300 210 781 450 96.992 1156 300 210 568 600 96.176 1104 300 210 284 750 93.088 ReferencesAmran, Y.
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cemconres.2003.08.004Bogas, J.
A., & Cunha, D. (2017).Non-structural lightweight concrete with volcanic scoria aggregates forlightweight fill in building’s floors. Construction and Building Materials,135, 151–163.
https://doi.org/10.1016/j.conbuildmat.2016.12.213Gündüz, L., & U?ur, I.
(2005).The effects of different fine and coarse pumice aggregate/cement ratios on thestructural concrete properties without using any admixtures. Cement andConcrete Research, 35(9), 1859–1864.
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