Influence of Chemical Admixtures on Fresh and Hardened Properties of Prolonged Mixed Concrete

Tarek Uddin Mohammed,Mohammad Abdul Awal,Farhan Shahriar,Abdul Munim,Shibly Mostafiz Apurbo,Tanvir Ahmed,Tahir Absar Mallick

doi:10.1155/2017/9187627

Abstract

Effects of different chemical admixtures on fresh and hardened properties of prolonged mixed concrete and their cost-effectiveness were investigated. Influence of sand to aggregate volume ratio, cement content, and use of chilled mixing water on the properties of prolonged mixed concrete was studied as well. Different concrete mixtures were prepared using five different types of chemical admixture (one water reducer based on lignosulfonate and four superplasticizers based on sulfonated naphthalene polymer, polycarboxylic ether, second-generation polycarboxylic ether polymer, and organic polymer), varying s/a ratio (0.40 and 0.45) and cement content (340 kg/m3 and 380 kg/m3) and using chilled mixing water. Slump tests were performed at 15-minute intervals to assess the fresh performance of each prolonged mixed concrete mixture. 100 mm by 200 mm cylindrical concrete specimens were prepared and tested for compressive strength, Young’s modulus, splitting tensile strength, and ultrasonic pulse velocity. Results indicate that concretes with sulfonated naphthalene polymer-based superplasticizer and second-generation polycarboxylic ether-based superplasticizer show best performances in both fresh and hardened states. Concrete with lignosulfonate-based water reducer exhibits poor performance in comparison with the concretes with superplasticizers. The cost per unit compressive strength of concrete with sulfonated naphthalene polymer-based superplasticizer is lower compared with the concretes with other types of chemical admixture.

Highlights

In recent years, the demand for ready-mix concrete (RMC) has increased rapidly in Dhaka city. e primary reasons behind this are convenience of using RMC in high-rise structures, shortage of space at construction site, saving of time related to the preparation of concrete on-site, and better quality of RMC compared to the conventional concrete
According to the JSCE 2007 guidelines for concrete [18], for normal weight ready-mix concrete, the minimum slump requirement at the place of unloading is 8 cm. erefore, in this study, the workability of each concrete mix was judged based on the time up to which the slump value was greater than 8 cm. e more the time, the better the workability
Second-generation polycarboxylic ether-based superplasticizer can be categorized as the second best chemical admixture in improving workability of fresh concrete

Summary

Introduction

The demand for ready-mix concrete (RMC) has increased rapidly in Dhaka city. e primary reasons behind this are convenience of using RMC in high-rise structures, shortage of space at construction site, saving of time related to the preparation of concrete on-site, and better quality of RMC compared to the conventional concrete. E primary reasons behind this are convenience of using RMC in high-rise structures, shortage of space at construction site, saving of time related to the preparation of concrete on-site, and better quality of RMC compared to the conventional concrete. Because of heavy tra c congestions throughout Dhaka, especially during weekdays, the time required to haul RMC from plant to construction site is very high. Erefore, keeping concrete workable for such a long time without compromising the required strength has become one of the most challenging tasks in the RMC industry. A good number of researches were carried out to understand the e ects of di erent types of chemical admixture on properties of concrete. Sugamata et al [7] investigated the e ect of chemical structure of polycarboxylic ether-based admixture on fresh performance of concrete and found that

Methods

Results

Conclusion