Effect of Different Chemical Admixtures on Fresh and Hardened Properties of M30 and M40 Grade Concrete

Abstract

Researchers in the field of concrete technology with the application of different admixtures are always in search of suitable admixtures to improve the workability as well as the strength of any concrete grade. An attempt was made in the present research to use chemical admixtures (superplasticizers) like sulphonated naphthalene based Apple Chemie AC-MENT-ALPHA-X5, polycarboxylic ether based Fosroc Auramix 350, sulphonated naphthalene based Fosroc Conplast SP 430, modified polycarboxylate based Du-bond DUPLAST PC P 2 and modified lignosulphate based Sika PLASTIMENT BV 40 for concrete grades M30 and M40. A literature survey revealed that all identified chemical admixtures are used for 20–25% reduced water content. A study was done to compare M30 and M40 grade concrete in both fresh and hardened states, taking water reduction into account. Experimental results showed that all admixtures demonstrate good paste-up consistency of up to 1%. As the percentage of admixtures increases, there is an increase in surface pores due to more significant air entrainment. Compressive strength results of 1% admixture content for Apple Chemie, Fosroc, and Du-bond were observed to be close to their characteristic compressive strengths for both grades, but Sika and Fosroc Auramix 350 have good compressive strength with less than 1%. As the grade of concrete improves, Conplast's effect reduces, but the Du-bond and Fosroc Auramix 350 perform excellently for split tensile strength. As the grade rises, all admixtures show increasing flexural strength levels. However, Auramix 350, with a 1.5% content for M30 grade, consistently outperforms Sika, which has a 1% content. It helped to employ up to 1% of all admixtures, but Sika reveals a cost increase of 2.5 to 7.3% for 1% and 1.5% admixture additions. The study found that Fosroc Auramix 350 could be used for both grades and still have good workability and strength.