Showing posts with label Concrete Experiments. Show all posts
Showing posts with label Concrete Experiments. Show all posts

Saturday, January 10, 2015

ACI Code Concrete Overlays for Pavement Rehabilitation Download PDF

Hydraulic cement concrete overlays are used as a rehabilitation technique for both existing concrete and asphalt pavements. Concrete overlays offer the potential for extended service life, increased structural capacity, reduced maintenance requirements, and lower life-cycle costs when compared with hot-mix asphalt overlay alternatives.


Concrete overlays have been used to rehabilitate existing concrete pavements since 1913 and to rehabilitate existing asphalt pavements since 1918 (Hutchinson 1982). Beginning around the mid-1960s, many highway agencies began to search for alternative means of rehabilitating existing pavements, and the use of concrete overlays increased significantly (McGhee 1994).

In the 1990s, there was an even higher increase in the use of concrete overlays, spurred by improvements in concrete paving technology. For example, the use of zero-clearance pavers, fast-track paving concepts, and high-early-strength concrete mixtures greatly increased the reliability of concrete overlays to serve as a  reliable rehabilitation alternative.

ACI Code
Concrete Overlays for Pavement Rehabilitation
ACI Committee 352
ACI 352.13R-06


Contents
Chapter 1 – Introduction
Chapter 2 – Concrete Overlay types and construction materials
Chapter 3 – Selection of Concrete Overlay Alternatives
Chapter 4 – Bonded Concrete Overlays
Chapter 5 – Unbonded Concrete Overlays
Chapter 6 – Conventional Whitetopping Overlays
Chapter 7 – Ultra –Thin and Thin whitetopping Overlays

Chapter 8 – References

Download ACI Code for free


Sunday, September 14, 2014

Determine the water absorption of coarse aggregate

The limit of water absorption by coarse aggregates is determined so as to calculate the appropriate amount of water to be added to the concrete mix, thus modifying the water cement ratio. A bone dry aggregate would necessitate, while for wet aggregate water contents should be reduced.
"Determine the water absorption by coarse aggregate "

Designation of Experiment

BS-812, Part 2: 1975

Apparatus

Balance, Oven, Dry and Soft absorbent cloth, shallow Trays
Determine the Water absorption of coarse aggregate

Materials Required

Sample of watered aggregates and water.

Procedure

Take a sample of coarse aggregates, wash to remove finer particles and dust and then immerse in water for 24+1/2 hours.
After this period, aggregate are taken out and dried with a dry absorbent cloth.
Weigh the aggregates and let this weight be A.
Place the aggregate in the oven at a temperature 100-110 for 24+1/2 Hours.
Remove the sample of aggregates from oven and cool in air, weight them and let this weight be B.

Observations and Calculations

Percentage water absorption =( (A-B)/B ) x 100
Wehere
A = Mass of saturated surface dry sample
B = Mass of Oven dried sample
A = 2225 gms
B = 2170 gms
Percentage Water Absorption = (55/2225) x 100 =2.47 %
Result
Percentage water absorption of coarse aggregate of given sample is 2.472 %.