EFFECT OF TYPES OF SUPERPLASTICIZER ON PROPERTIES OF PASTE AND MORTAR MADE WITH A BINDER OF BOTTOM ASH AND CALCIUM CARBIDE RESIDUE

Abstract

This research investigated the effect of melamine sulphonate (MS) and
polycarboxylate (PC) superplasticizers on properties of paste and mortar
using ground bottom ash (GBA) mixed with ground calcium carbide residue
(GCR) as a binder. The optimum proportion between GBA:GCR was
determined and it was found that the optimum proportion was 70:30 by
weight to obtain the highest compressive strength. The effects of MS and PC
superplasticizers on normal consistency and setting times of GBA-GCR pastes
and compressive strengths of GBA-GCR mortars were investigated. The
results showed that at the same dosage, PC superplasticizer could decrease
more effectively the water demand at normal consistency than MS
superplasticizer. The setting times of GBA-GCR pastes were between 235 to
390 min. However, the setting time of paste was shorter with the increased of
PC superplasticizer dosage between 0.2 to 1.0% by weight of binder. With
0.2% by weight of binder, MS superplasticizer could reduce the setting time
of paste but the setting time tended to increase with the increased of MS
superplasticizer dosage from 0.5% to 1.0% by weight of binder. The highest
compressive strength of GBA-GCR mortar at 90 days was 206 ksc. In
addition, the mortar containing PC superplasticizer had higher compressive
strength than that of mortar containing MS superplasticizer, especially at a
low water to binder ratio (w/b ratio of 0.45) of mortar. As the results, GBA
and GCR can be used as a new binder and the workability of the binder could be
improved by using superplasticizer. Moreover, use of PC superplasticizer
could decrease setting times of paste and gave better compressive strength of
mortar than that with MS superplasticizer. Moreover, there was little or no
significant difference for the cost of using both superplasticizers when the
w/b ratio and flow of both mortars were kept the same.