الجزء الثاثني من البحث مقدم من قبل الطالب احمد جلال خليل جدوع

I CHAPTER FOUR

Results and Discussion

4 . Results and Discussion

Tables { 4.1 to 4.8}show mix properties and the result of the testing specimens. Figures { 4.1 to 4.4 } indicate the relationship between the parameters measured in this project.

Discussion :-

4.1 Compressive strength

In general Light Weight Concrete {LWC} are not as strong as normal weight concrete, and thus the concrete strength will depend on a number of consideration. strength will depend on the type and quality of aggregate used, the size of fraction used, the amount of aggregate used, the type and quality of the binder used, and type of admixture.

Compressive strength were measured up to 56 days as shown in table 4.3 , 4.4 and in figs {4.1 and 4.2} the result indicate that there are a difference in the compressive strength, were the percentage of the industrial sand is changed from 0.5 to 2 .

The results show also increasing of compressive strength with age. for mix 1, the percentage of compressive strength from 7 days to 56 days is about 24% and about 21.5 % for mix 2 and so on . this increasing not much big, because the absence of silica fume help the concrete to get strength at early ages.

From the results also .thot the compressive strength affected by the type of the curing. Soaking in 23°C water gave higher results. But still the compressive strength for self using good when compare the specification.

The compressive strength between { 20.87 -15.22 }Mpa will be considered as structural concrete, and compressive strength between { 11 - 18} Mpa as moderate and below that will be insulation.

From table { 4 - 8 }, when compared with concrete block { density 2400 kg/m3} cellular concrete mixes {densities 1200 -1600 kq/m" } give higher compressive strength.

4.2 Absorption

Results for the different concrete mixes are shown in table ( 4.5 ) and Fig ( 4.3) .

The absorption of the mixes are between 11.9% to 14% . Comparing with concrete block. It is clear that the absorption are in agreement with the specification, although the mixes have densities more less than concrete block.

Table ( 4.8) show the specification of concrete block and thermo stone according to Iraqi specification ( No. 1077/1987 ) ( 1441/2000) respeetively. From the table .and , when compared with thermo stone the mixes result are very good.

4.3- 28 days - air dry density :-

The 28 - Air dry density of all mixes are percentage in table ( 4 - 6) . Results of the different concrete mixes show that using of the industrial sand and getting the air bubbles inside the concrete reduce the density. Mix 1 gave 1600 kg/m3 when the proportion of the industrial sand to ordinary sand 1:0,5, but when this proportion increased the density was reduced to 1200 kg/ m3 .

Act manual, indicate the relation between compressive strength and densities. concrete with less than 350 kg/m3 will have a strength between 1-3 Mpa. Densities between (900-1850) will give strength more than 20 Mpa. The result in this project are with accommodation of the Act manual.

4.4 Thermal Conductivity

The importance reason for production of cellular concrete is thermal insulation. Table ( 4. 7 ) show the results.

According to Act [ 15 J , thermal conductivity factor ( k) calculated from the equation :-

K :- thermal conductivity factor w/m.kcal

:- dry density kg/m3

Comparing with ordinary concrete ( k = 1.45 w/m.k cal) I the results show good properties of thermal insulation.

4.5 Self Curing

The essential way to achieve the designed properties of concrete is proper curing. This mean avoiding water evaporation at the surface of the concrete member and supplying water from the exterior. If enough water was available to cement paste for hydration to proceed I the concrete will achieve excellent properties. The concrete with w/c lower than 0.40 in combination with the high cement content and to addition of silica fume I the concrete will show a high rate of hydration and the well known relatively high compressive strength of early age. So creating a water supply in the concrete which is independent of the of the environment is a good idea. The water bubbles used in this research contain amount of water I in which will supply the concrete the desired amount of water for hvdration . The compressive strenqth not much affected.

Results: -

Table 4.1 : Mix proportion for natural sand to industrial sand by volume

, CHAPTER FIJIE

Conclusions

5. Conclusions

Baste on the results of this project the following conclusions are drawn:

1- Cellular concrete be product using cement .sand .industrial sand, silica fume and superplistaziar .

2- At 28 days the compressive strength for mixes when cured in (23°c) water are between (8.8 -19. 7)Mpa and ( 8.28 -15.67 ) Mpa for self curing according to mix proportion. When the cells increased compressive strength decreased.

3- At 56 - days the compressive strength for ( 23 ° C) water curing are

( 10.87 -20.87 ) Mpa .

4- Absorption for the mixes are between ( 11.9 % -14 % l . comparing with thermiston ( 45 % ) , these results are very good.

5- 28-days dry density are from ( 1200 -1600 ) kq/m? .

6- All the mixes can be considered as structural concrete.

7- Adding silica fume and superplasticizer increase the compressive strength of concrete.

8- Cost of this type of concrete same as concrete but cheaper the therrniston .

References

References

3. AM Neville. II Properties of concrete II 2003 .

5. S. R. Boyd I T. A. Holm I and T. W. Bremner II performance of structural light weight concrete made with a potentially reactive natural sand "I sixth CANMET lAC! International con terence on durability of concrete. June 2003 6. S. Weber and H. W. Reinhardt II Modeling the internal curing of high - strength concrete using light weight aggregates ". 7. Concrete admixtures hand book properties I science and technology V. S . RAMACHANDRAN -1984. 8. G. C. Hoff II Internal curing of concrete using light weight aggregate "I sixth CANMET lAC! International conference on durability of concrete. June 2005 9. R. N. Swamy II lightweight aggregate concrete" : The Flagship of sustainable construction ""I sixth CANMET lAC! International conference on durability of concrete. June 2003 10. Nadia S. I Daad M. II using polystyrene in production of cellular lightweight masonry concrete having high moisture protection [ZJ vol. 14 I NO.4 I 2003 مجلة علوم الرافدين 11. II Typical characteristics of silica fume" From Internet I 2007 .المواصفة القياسية العراقية رقم ( 5 ) لسنة 1984 السمنت البورتلاندي 12- 13. ASTM C39 II Standard test method for compressive strength of lightweight concrete cube. Annual book of ASTM I standards I vol. 04. 02 I 1989. 14. ASTM 642 "Standard method for specific gravity I Absorption and voids in hardend concrete" Annual book of ASTM I standards I vol. 04 . 02 I 1989. 15. AC! Manual of concrete practice 1985 part 1 . Materials and general properties of concrete ( P.213 R.79 ) .

1. II High - strength structural lightweight concrete [ZJ From Internet I 2003 . 2. ACI Manual of concrete practice. Part 1 . Guide for use of admixtures in i ~ concrete. American institute. U.S.A. 1985 .

4. Nadia S. I Daad M. II Foamed concrete masonry blocks using local raw materials II Raffider Jurnal I Mosul University vol. 10 I No.2 .2002.