Self Compacted Concrete
SCC was developed to ensure adequate compaction through self- consolidation and facilitate placement of concrete in structures with congested einforcement and in restricted areas. SCC can be described as a high performance material which flows under its own weight without requiring vibrators to achieve consolidation by complete filling of the formworks even when access is hindered by narrow gaps between reinforcement bars . The high flowability of SCC makes it possible to fill the formwork without vibration .
The constituent materials used for the production of SCC are the same as those for conventionally vibrated normal concrete except that SCC contains a lesser amount of aggregates and larger amount of powder (cement and filler particles smaller than 0. 25 mm) and special plasticizer to enhance flowability. Fly ash, glass filler, limestone powder, silica fume, etc. are used as the filler materials. High flowability and high segregation resistance of SCC are obtained by using: (i) a larger quantity of fine particles, i. e. limited aggregate content (coarse aggregate: 50% of the concrete volume and sand: 40%.
Shrinkage and creep of the SCC mixtures have not been found to be greater than those of traditional vibrated concrete [9, 19, and 20]. Studies on durability characteristics of SCC, namely, water absorption, initial surface absorption, water permeability, and chloride permeability, have shown that SCC has either performed better or same as the normal concrete [9, 10, 21] Minerals Dhahran-31261, saudi Arabia Fax: 966-3-8602879 E-mail: [email protected] edu. Paper Received 25 June 2007; Revised 21 January 2008; Accepted 22 March 2008 October 2008 The Arabian Journal for Science and Engineering, Volume 33, Number 2B 437 In view of the fact that SCC has not yet made any inroad into Saudi Arabia’s construction industry, this study was undertaken with the aim to shed some informative data on SCC made from locally available aggregates. Most of the coarse aggregates available in the eastern region of Saudi Arabia are crushed tertiary age weaker dolomitic limestone.
As the aggregates are porous, highly absorptive, relatively soft, and excessively dusty, they can be classified as “marginal”. The aeolian dune sands in the coastal areas form the main source of fine aggregate. These sands are essentially fine grained and have narrow grading with excessive dust. Nearly all the material passes No. 30 sieve and an appreciable portion, 10 to 20%, passes # 100 sieve. Both coarse and fine aggregates from local sources can be characterized as marginal, as their properties do not meet the standards of sound quality.
This study explores the use of local marginal aggregates in producing SCC that has reasonable strength and no short-term durability implications. The findings of this study may ncourage further research and possible adoption of SCC in local construction. 2. EXPERIMENTAL PROGRAM 2. 1 . composition of Trial Mixes and Their properties For selecting a suitable mix using local marginal aggregates, trial mixes were considered by varying the mix parameters, such as quantity of filler and superplasticizer and fine aggregate/coarse aggregate ratio, while keeping the water/powder ratio constant.
The specific gravity of Type I cement used was taken as 3. 15 as per the product information available from the manufacturer. The coarse aggregates used in this tudy were crushed limestone processed from the local quarries in Abu Hadriah, Saudi Arabia. The maximum aggregate size was 20 mm and the grading of coarse aggregates used corresponds to ASTM C 33 (size number 7) . The average values of specific gravity and absorption of the coarse aggregate, determined in accordance with ASTM C 127 , were 2. 5 and 1. 5%, respectively. Local dune sand was used as fine aggregate.
The specific gravity and absorption of the fine aggregate were typically 2. 6 and 0. 57%, respectively. A highly pulverized fly ash commercially known as [email protected]  was used as a filler. The specific gravity [email protected]  used in this study was 2. 15. Superplasticizer by the trade name of Structuro 220 was used. The specific gravity of the superplasticizer as given by the supplier is 1. 08 and the pH is 6. 5 with chloride content of less than 0. 1%. A high performance commercially available cohesion agent Structuro 420, specially designed to ensure a stabilizer.