Abstract
This paper investigates durability of no fine concrete containing demolished concrete as coarse aggregate after crushing to different sizes. Different no fine concrete mixes were considered using Portland cement type I with two types of coarse aggregates, crushed demolished concrete and crushed natural gravel were used with two ratios by weight (1:5 and 1:7) C/Agg. Graded aggregate and single size were used with a maximum size of 20 mm. W /C ratio was kept as 0.4 for all mixes and super-plasticizer was required to keep the same flow and compaction factor value for all mixes. Cube specimens with 150mm were cured and divided to two parts, the first part was exposed to 60 cycles of freezing- thawing; the second part of the sample was immersed in Nitric Acids solution with pH of 3.5 for (7, 28, 90 and 180 days) and then tested for compressive strength. The results indicated that it is possible to produce homogenous and workable mixes by using demolished crushed concrete as coarse aggregate. The compressive strength after cycles of freezing- thawing and immersing in Nitric acid (HNO3) at (7, 28, 90 and 180) days was decreased for samples made with crushed demolished concrete. Also it is found that the performance of concrete mixes containing graded coarse aggregate and 1:5 cement/aggregate ratios was better than other mixes.
Highlights
No fine concrete is a method of producing lightweight concrete by removing the sand from conventional concrete
The results indicate that the compressive strength for no fine concrete specimens that subject to freezing- thawing decrease with increase percentage of coarse aggregate/cement ratio
Based on the results of this research, the following conclusions may be drawn: 1- The workability of no fine concrete produced by demolished concrete as coarse aggregate is less than the workability of no fine produced by natural crushed aggregate
Summary
No fine concrete is a method of producing lightweight concrete by removing the sand from conventional concrete. This concrete is consisting of only cement, coarse aggregate and water [1]. Because of some of the advantages it possesses over the conventional concrete, no fines concrete is becoming popular. To reduce the problem of cumulative waste, dumping should be used in an environmentally safe method either as economical and beneficial purposes or as raw materials for other products. The use of demolished concrete for the purpose of manufacture of lightweight concrete can represent the double benefits of using this waste, cleaning the environment, and by the production of good concrete which can be used [2]. Durability of concrete may be defined as the ability of concrete to resist weathering action, chemical attack and abrasion while maintaining its desired engineering properties
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