Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Modulus of rupture


Effect of Compaction Methods on the Properties of Roller Compacted Concrete

Hisham Khalid Ahmed; Azal Thair Abdulrazzak

Engineering and Technology Journal, 2014, Volume 32, Issue 10, Pages 2454-2464

Roller compacted concrete (RCC) is a technology characterized mainly use of roller for compaction. This construction method permits considerable reduction in costs and construction time of dams and roads. The main aim of this work is to investigate the influence of compaction methods on the properties of RCC. the experimental program included preparing cylindrical specimens with (diameter of 150 mm by height of 300 mm) for measuring the compressive strength, splitting tensile strength and absorption. And it also includes prism specimens with (100*100*400) mm for measuring the modulus of rupture. These specimens were compacted by using different compaction methods, dynamicly (modified proctor hammer compaction (CBR test), vibrator table, and vibrator table with CBR test) and statically (compacting pressure (compacting pressure 10 MPa, 15 MPa and 20 MPa).
Results show that the compaction methods have a noticeable effect on the properties of RCC. The results also indicated that using vibrator table with CBR show an increase in the compressive strength, splitting tensile strength and modulus of rupture by 23%, 14% and 13%, respectively as compared with compacted by vibrator table only. The results also show that using compacting pressure 20 MPa show an increase in the compressive strength, splitting tensile strength and modulus of rupture by 31%, 27%, and 39%, respectively as compared with that made by compacting pressure 10 MPa.

Using Citric Acid As An Admixture and It's Influence on Some Properties of Concrete

Wasan I. Khalil

Engineering and Technology Journal, 2009, Volume 27, Issue 1, Pages 32-41

The objective of this investigation is to find the effectiveness of the citric acid as
retarding admixture. The experimental results indicate that the optimum dosage of citric
acid is 0.02% by weight of cement. This dosage causes a delay in initial and final setting
time of 1:42 and 3:18 hour: minute, respectively; and a reduction in water-cement ratio
of 13% relative to reference concrete mix. So, citric acid can be classified according to
ASTM-C494 as water-reducing and retarding chemical admixture type D.
The investigation also extends to evaluate the effect of using citric acid on
properties of concrete such as, compressive strength, splitting tensile strength, modulus
of rupture and dynamic modulus of elasticity at normal conditions and after exposure to
salt solutions. Generally the results indicate that using citric acid in concrete enhance it's
properties at normal conditions, the percentage increase in compressive strength,
splitting tensile strength, modulus of rupture and dynamic modulus of elasticity at age
180 days was about 56%, 13%, 24% and 8% respectively relative to reference concrete.
Also it was observed that concrete containing citric acid has good performance after 180
days exposure to salt solution in comparison with reference concrete.