A study of the influence of hardening accelerator substances toward concrete mix workability and compressive strength of concrete.

Currently, admixture substances - which are used as concrete hardening accelerator are available on several factories. With faster hardening process, the construction period can be shorten therefore the building cost become competitively. This research aims is to compare the influence of several hardening accelerators toward the concrete mix workability and normal compressive strength. Five types of concrete were made in this research (one type of normal concrete and 4 types of concrete with admixtures), which were tested after 3, 7, 14 and 28 days. Concrete mix was designed with water/cement ratio (w.c.r.) of 0.50, slump value of 50 mm, and coarse aggregate maximum granule size of 40 mm. Admixtures used were Sikamet NN, Bestmittel, BV Special and Superplastet with minimum dosage based on the brochure of every admixtures. The test results showed that the addition of Sikamet NN, Bestmittel, BV Special and Superplastet increased the slump value of concrete mix and compressive strength of concrete. The compressive strength gain of concrete was also different between one to another although the 28 days concrete gave relatively same degree of compressive strength - except for Sikamet-NN. The Sikamet-NN liquidity was too high and no increasing of compressive strength gain, therefore, Sikamet-NN acted more as superplasticizer, where as the other three admixtures acted both as plasticizer and hardening accelerato