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The cellular structure of a LWA makes it inherently insulating, and this factor is responsible for the high thermal insulation of the LWAC. Also, this type of LWC has generally a lower thermal expansion than Normal Weight Concrete (NWC), therefore, it is more stable at elevated temperature than many dense aggregate concrete. This property, combined with the better thermal insulation, produce the inherent fire. Lightweight aggregate (LWA). There are also papers dealing with the effect of high temperatures on chemical and mechanical properties of LWC [1-4], however, there are few papers dealing with the effect of high temperatures on chemical and mechanical properties of Foamed Concrete (FC) [9]. So, this investigation is suggested to study the properties of foamed concrete, and try to improve their properties by using local and low cost materials. In this work, compressive and density are to be measured. The analytical study involves thermal conductivity analysis of the LWAFC.
The heat exposure may be found in some industrial installations where concrete is used in places exposed to sustained elevated temperatures ranging from (100-1000) ?C as in foundation for blast furnaces and coke batteries, furnaces wall and dampers, industrial chimneys, flues, kilns and nuclear- reactors [3].
Since concrete is a composition of different materials, the behaviour of concrete under elevated temperatures depends on its constituents. The aggregate type and structure of cement paste has a great effect on thermal conductivity of concrete. The highly porous microstructure of lightweight aggregate (LWA) gives it low density and better insulation and that makes the concrete made with LWA exhibit lower thermal conductivity than that of normal weight concrete (NWC). Therefore, Lightweight Aggregate Foamed Concrete (LWAFC) provides more effective fire protection than other types of concrete as it is less liable to spalling and has a higher thermal insulation [2].
Therefore, many studies have been carried out to investigate the properties of Lightweight Concrete (LWC) exposed to elevated temperatures by using various

Experimental investigation
The effect of various test parameters on the properties of LWAC and LWAFC. All mixes were exposed to different temperature levels and the period of exposure at the maximum temperature was two hours.
The investigation was based on using locally manufactured cement Type I (OPC) produced by Al Kubaisa Cement Factory, whose chemical and physical properties are shown in Table-1 and Porcelanite crushed
stone obtained from the north of Al-Rutba Town in Al- Anbar Governorate - Iraq. Table-2 lists some important physical and chemical properties for coarse and fine Porcelanite aggregate. Foaming agent type EUCO was used in this study to produce LWAFC with 2% foaming agent by weight of water [9]. Table-3 indicates the technical description of the foaming agent.
The coarse aggregate used was 10 mm in all mixes. The fine aggregate used Porcelanite as partial and total replacement with local natural sand whose fineness modulus 2.61. Its gradation lies in zone 3 and the grading test results conform to Iraqi Specification No.45/1984 as shown in Figures 1 and 2 which show grading of fine and coarse aggregate used in this investigation. Potable water of Al-Risafa, Baghdad, was used throughout this investigation for mixing and curing.

Test parameters
The test parameters investigated were:
- Porcelanite as fine aggregate replacement, partial and total replacement;
- Level of exposure temperatures, at an age of 60 days, the specimens were heated in an electric furnace, four maximum temperature levels were selected (200, 300, 400 and 700?C) the period of exposure at the maximum temperature was two hours.

MIXTURE PROPORTIONS AND DETAILS
Investigation was carried out in three different series and mix proportioning was calculated according to ACI 211-98 [10]. An extensive series of tests were conducted to develop suitable LWAC, and LWAFC reinforced with fiber, are classified into classified into two series:
- Series I - MSP, MSPP, MPP: mixtures details are presented in Table-4
- Series II - MSPF, MSPPF, MPPF: mixtures details













Concrete Mixing, Test Specimens, Curing, Condition, and Testing Details
The mixing sequence was as follows: coarse aggregate and fine aggregate, added in the mixer and mixing continued for 1minute, then the required quantity of dry cement was added, and mixing continued for 3 minutes at which a good homogenous mix was produced.
Two thirds of the required quantity water were then added to the dry materials, and the remaining water and the required quantity of foaming agent were added to the machine to make foam which was then added to the mix [9].


Influence of high elevated temperatures on LWAC and LWAFC

Loss of weight
All series exhibited smaller loss in weight with respect to exposure temperature are plotted in Figures 3 and 4. The decrease in weight was not more than 2% at 200 ºC and 7% at 300 ºC, for all mixes. This is due to the removal of the capillary and adsorbed water from the cement paste. On the other hand, it has become obvious that there is an increase in the loss of weight at a temperature above 300 ?C, and reduction of the weight is ranging from a minimum of about 17 % to a maximum of about 41 % at 700 ?C. This is due to the further dehydration of the cement paste as a result of the decomposition of calcium hydroxide.
It has also been noticed that in Series I, sanded- LWAC specimens (MSP, and MSPP) showed a larger reduction in their weight compared to MPP specimens containing fine Porcelanite aggregate as a total replacement of natural sand. The results show that the MPP mixes are more thermal stable than the other mixes and the thermal stability of the concrete depends largely on the thermal stability of the aggregate.



COMPRESSIVE STRENGTH
The residual compressive strength of Series I, and II decreases with the increase of temperature degree Figures 5 and 6. The range of properties of Series I and II concrete presented in Table-5. Residual compressive strength at 200 ?C for Series I is approximately (70, 83, and 86) % of MSP, MPPS, and MPP respectively. Residual compressive strength at 300 ?C for Series I is approximately (62, 69, 80) % of MSP, MPPS, and MPP respectively. At 400 ?C the residual strength is (38, 44, and
50) % for MSP, MPPS, and MPP respectively. At 600 ?C the residual strength is approximately (23, 34, and 41) % for MSP, MPPS, and MPP respectively. Residual compressive strength at 700 ?C for Series I is approximately (11, 20, and 23) % for MSP, MPPS, and MPP respectively. Residual strength of MPP is higher compared to MSP when subjected at different temperatures. The rate of loss of strength is significantly at 700 ?C compared to the others, especially for MSP. The residual strength at 600 ?C is equivalent to half the residual strength at 300 ?C. At high temperature, the dehydration of cement paste results in its gradual disintegration. Because the paste tends to shrink and aggregate expands at high temperatures of above 600 ?C, the bond between the aggregate and the paste is weakened resulting a great reduction in strength as confirmed in test results [15, 16]. The deterioration of strength at elevated temperatures for such concretes can be attributed to the coursing of the pore structure and the increase in pore diameter [15, 16, and 17].
The test results indicated that each temperature range for Series II is plotted in Figure-6. Residual compressive strength at 200 ?C for Series II is approximately (80, 87, and 91) % of MSPF, MPPSF, and MPPF respectively. Residual compressive strength at 300?C for Series II is approximately (69, 75, 85) % of MSPF, MPPSF, and MPPF respectively. At 400 ?C the residual strength is (61, 63, and 69) % of MSPF, MPPSF, and MPPF respectively. At 600 ?C the residual strength is approximately (47,49, and 50) % of MSPF, MPPSF, and MPPF respectively. Residual compressive strength at 700
?C for Series II is approximately (40, 44, and 47) % of MSPF, MPPSF, and MPPF respectively.
Generally, the strength loss in Series II is lower compared to Series I when the temperature is varied from 200 to 700 ?C. For instance, at 700?C, the residual strength (40, 44, and 47) % of MSPF, MPPSF, and MPPF
respectively which are considered higher compared to Series I. This is an indication of better performance of LWAFC in retaining the strength at elevated temperature


as compared with LWAC. This can be attributed to the less dense pore structure of Series II (compared to Series
I) due to the presence of comparatively porous cement paste and lightweight aggregate (Porcelanite).
At 700 ?C, Series I, and Series II specimens experience considerable cracks as well as spalling. The color of specimens also changes to pink. The specimens undergo surface features when exposed to 600 ?C also showed color changes as well as some edge cracks but not as severe as those exposed to 700 ?C as shown in Figure-7. Series II should exhibit more resistance to high elevated temperatures than Series I due to lesser tendency to spall and loss of lesser proportion of its original strength with the rise in temperature



CONCLUSIONS
The following conclusions can be drawn from this study:
? The addition of foaming agent by 2% was beneficial in improving the workability of LWAC. The slump values of LWAFC between 242 to 284 mm showed satisfactory workability with no segregation or excessive bleeding specially for MPPF mixture.

? The compressive strength and density decrease with the increase of the Porcelanite replacement with sand. The proportional loss in strength between normal concrete LWAFC containing 50% (MSPPF) and 100% fine Porcelanite aggregate (MPPF) showed a little loss in mechanical properties compared with the sanded-LWAFC (MSPF).

? The behavior of Series I mixture under compressive strength was more sensitive to elevated temperatures than that of Series II.

? The residual compressive strength of series II specimens was more than series I especially when exposed to high temperatures, the residual strength is (69, 50, and 47) % of MPPF at 400 ?C, 600 ?C, and 700?C respectively.

? MSP specimens have a minimum residual strength comparison with the others, especially at high elevated temperatures, equal to (38, 23, and 11) % at 400 ?C, 600 ?C, and 700 ?C respectively.

Submitted: October 04, 2018

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Submitted: October 04, 2018

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The cellular structure of a LWA makes it inherently insulating, and this factor is responsible for the high thermal insulation of the LWAC. Also, this type of LWC has generally a lower thermal expansion than Normal Weight Concrete (NWC), therefore, it  is more stable at elevated temperature than many dense aggregate concrete. This property, combined with the better thermal insulation, produce the inherent fire. Lightweight aggregate (LWA). There are also papers dealing with the effect of high temperatures on chemical and mechanical properties of LWC [1-4], however, there are few papers dealing with the effect of high temperatures on chemical and mechanical properties of Foamed Concrete (FC) [9]. So, this investigation is suggested to study the properties of foamed concrete, and try to improve their properties by using local and low cost materials. In this work, compressive and density are to be measured. The analytical study involves thermal conductivity analysis of the LWAFC.

The heat exposure may be found  in some industrial installations where concrete is used in places exposed to sustained elevated temperatures ranging from (100-1000) °C as in foundation for blast furnaces and coke batteries, furnaces wall and dampers, industrial chimneys, flues, kilns and nuclear- reactors [3].

Since concrete is a composition of different materials, the behaviour of concrete under elevated temperatures depends on its constituents. The aggregate type and structure of cement paste has a great effect on thermal conductivity of concrete. The highly porous microstructure of lightweight aggregate (LWA) gives it low density and better insulation and that makes the concrete made with LWA exhibit lower thermal conductivity than that of normal weight concrete (NWC). Therefore, Lightweight Aggregate Foamed Concrete (LWAFC) provides more effective fire protection than other types of concrete as it is less liable to spalling and has a higher thermal insulation [2].

Therefore, many studies have been carried out to investigate the properties of Lightweight Concrete (LWC) exposedtoelevatedtemperaturesby   usingvarious

 

Experimental investigation

The effect of various test parameters on the properties of LWAC and LWAFC. All mixes were exposed to different temperature levels and the period of exposure at the maximum temperature was two hours.

The investigation was based on using locally manufactured cement Type I (OPC) produced by Al Kubaisa Cement Factory, whose chemical and physical properties are shown in Table-1 and Porcelanite crushed

 

stone obtained from the north of Al-Rutba Town in Al- Anbar Governorate - Iraq. Table-2 lists some important physical and chemical properties for coarse and fine Porcelanite aggregate. Foaming agent type EUCO was used in this study to produce LWAFC with 2% foaming agent by weight of water [9]. Table-3 indicates the technical description of the foaming agent.

The coarse aggregate used was 10 mm in all mixes. The fine aggregate used Porcelanite as partial and total replacement with local natural sand whose fineness modulus 2.61. Its gradation lies in zone 3 and the grading test results conform to Iraqi Specification No.45/1984 as shown in Figures 1 and 2 which show grading of fine and coarse aggregate used in this investigation. Potable water of Al-Risafa, Baghdad, was used throughout this investigation for mixing and curing.

 

Test parameters

The test parameters investigated were:

  • Porcelanite as fine aggregate replacement, partial and total replacement;
  • Level of exposure temperatures, at an age of 60 days, the specimens were heated in an electric furnace, four maximum temperature levels were selected (200, 300, 400 and 700?C) the period of exposure at the maximum temperature was two hours.

 

MIXTURE PROPORTIONS AND DETAILS

Investigation was carried out in three different series and mix proportioning was calculated according to ACI 211-98 [10]. An extensive series of tests were conducted to develop suitable LWAC, and LWAFC reinforced with fiber, are classified into classified into two series:

  • Series I - MSP, MSPP, MPP: mixtures details are presented in Table-4
  • Series II - MSPF, MSPPF, MPPF: mixtures details

 

 

 

 

 

 

 

 

 

 

 

 

 

Concrete Mixing, Test Specimens, Curing, Condition, and Testing Details

The mixing sequence was as follows: coarse aggregate and fine aggregate, added in the mixer and mixing continued for 1minute, then the required quantity of dry cement was added, and mixing continued for 3 minutes at which a good homogenous mix was produced.

Two thirds of the required quantity water were then added to the dry materials, and the remaining water and the required quantity of foaming agent were added to the machine to make foam which was then added to the mix [9].

 

 

Influence of high elevated temperatures on LWAC and LWAFC

 

Loss of weight

All series exhibited smaller loss in weight with respect to exposure temperature are plotted in Figures 3 and 4. The decrease in weight was not more than 2% at 200 ºC and 7% at 300 ºC, for all mixes. This is due to the removal of the capillary and adsorbed water from the cement paste. On the other hand, it has become obvious that there is an increase in the loss of weight at a temperature above 300 ?C, and reduction of the weight is ranging from a minimum of about 17 % to a maximum of about 41 % at 700 ?C. This is due to the further dehydration of the cement paste as a result of the decomposition of calcium hydroxide.

It has also been noticed that in Series I, sanded- LWAC specimens (MSP, and MSPP) showed a larger reduction in their weight compared to MPP specimens containing fine Porcelanite aggregate as a total replacement of natural sand. The results show that the MPP mixes are more thermal stable than the other mixes and the thermal stability of the concrete depends largely on the thermal stability of the aggregate.

 

 

 

COMPRESSIVE STRENGTH

The residual compressive strength of Series I, and II decreases with the increase of temperature degree Figures 5 and 6. The range of properties of Series I and II concrete presented in Table-5. Residual compressive strength at 200 ?C for Series I is approximately (70, 83, and  86)  %  of  MSP,  MPPS,  and  MPP  respectively. Residual compressive strength at 300 ?C for Series I is approximately (62, 69, 80) % of MSP, MPPS, and MPP respectively. At 400 ?C the residual strength is (38, 44, and

50) % for MSP, MPPS, and MPP respectively. At 600 ?C the residual strength is approximately (23, 34, and 41) % for MSP, MPPS, and MPP respectively. Residual compressive strength at 700 ?C for Series I is approximately (11, 20, and 23) % for MSP, MPPS, and MPP respectively. Residual strength of MPP is higher compared to MSP when subjected at different temperatures. The rate of loss of strength is significantly at 700 ?C compared to the others, especially for MSP. The residual strength at 600 ?C is equivalent to half the residual strength at 300 ?C. At high temperature, the dehydration of cement paste results in its gradual disintegration. Because the paste tends to shrink and aggregate expands at high temperatures of above 600 ?C, the bond between the aggregate and the paste is weakened resulting a great reduction in strength as confirmed in test results [15, 16]. The deterioration of strength at elevated temperatures for such concretes can be attributed to the coursing of the pore structure and the increase in pore diameter [15, 16, and 17].

The test results indicated that each temperature range for Series II is plotted in Figure-6. Residual compressive strength at 200 ?C for Series II is approximately (80, 87, and 91) % of MSPF, MPPSF, and MPPF respectively. Residual compressive strength at 300?C for Series II is approximately (69, 75, 85) % of MSPF, MPPSF, and MPPF respectively. At 400 ?C the residual strength is (61, 63, and 69) % of MSPF, MPPSF, and MPPF respectively. At 600 ?C the residual strength is approximately (47,49, and 50) % of MSPF, MPPSF, and MPPF respectively. Residual compressive strength at 700

?C for Series II is approximately (40, 44, and 47) % of MSPF, MPPSF, and MPPF respectively.

Generally, the strength loss in Series II is lower compared to Series I when the temperature is varied from 200 to 700 ?C. For instance, at 700?C, the residual strength (40,  44,  and  47)  %  of  MSPF,  MPPSF,  and  MPPF

respectively which are considered higher compared to Series I. This is an indication of better performance of LWAFC in retaining the strength at elevated temperature

 

 

as compared with LWAC. This can be attributed to the less dense pore structure of Series II (compared to Series

I) due to the presence of comparatively porous cement paste and lightweight aggregate (Porcelanite).

At 700 ?C, Series I, and Series II specimens experience considerable cracks as well as spalling. The color of specimens also changes to pink. The specimens undergo surface features when exposed to 600 ?C also showed color changes as well as some edge cracks but not as severe as those exposed to 700 ?C as shown in Figure-7. Series II should exhibit more resistance to high elevated temperatures than Series I due to lesser tendency to spall and loss of lesser proportion of its original strength with the rise in temperature

 

 

 

CONCLUSIONS

The following conclusions can be drawn from this study:

  • The addition of foaming agent by 2% was beneficial in improving the workability of LWAC. The slump values of LWAFC between 242 to 284 mm showed satisfactory workability with no segregation or excessive bleeding specially for MPPF mixture.

 

  • The compressive strength and density decrease with the increase of the Porcelanite replacement with sand. The proportional loss in strength between normal concrete LWAFC containing 50% (MSPPF) and 100% fine Porcelanite aggregate (MPPF) showed a little loss in mechanical properties compared with the sanded-LWAFC (MSPF).

 

  • The behavior of Series I mixture under compressive strength was more sensitive to elevated temperatures than that of Series II.

 

  • The residual compressive strength of series II specimens was  more than series I especially when exposed to high temperatures, the residual strength is (69, 50, and 47) % of MPPF at 400 ?C, 600 ?C, and 700?C respectively.

 

  • MSP specimens have a minimum residual strength comparison with the others, especially at high elevated temperatures, equal to (38, 23, and 11) % at 400 ?C, 600 ?C, and 700 ?C respectively.

 


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