Use of Boron Compounds as Grinding Aids with Alcohol Amines and Their Effect on Portland Cement Setting Points

Murat Çallı,Erol Pehlivan

doi:10.1155/2018/3187984

Abstract

Milling aids have been predominantly developed to increase the performance or grinding capacity of cement products, and alcohol amines have been used as grinding aids in cement grinding processes for many years. Moreover, the setting point of cement produced with grinding aids is most often changed. In this study, the effects of alkanolamines and boron compounds in different mixing amounts as grinding aids on the set point of cement were researched. Triethanolamine (TEA) and triisopropanolamine (TIPA) were used as alkanolamines and boric acid (BA) and anhydrous borax (AHB) as the boron compounds. It is evident that BA with TEA had a small effect on the cement setting point where the former decreased the retarding effect of the latter, but BA had no effect with TIPA. AHB decreased the retarding effect of TEA but had no effect with TIPA on setting times. When the boron compounds were added to TEA, they accelerated the initial setting points of cement by 15 to 20 minutes and the final setting points by 25 to 30 minutes according to the amount of TEA used.

Highlights

A hydration reaction instantly starts when water is mixed with cement to form a paste that first begins to lose its plasticity and stiffens and hardens [1]. e main phases, C3A, C3S, C2S, and C4AF, react quickly with water to produce a jell-like mixture that starts solidifying. e action of changing from a fluid state to a solid state is called setting which is the transformation process from the initial state to the final state
In experiments carried out with 100% TEA and TIPA, the water demand of ground cement was increased to 26.2 ± 0.1%. is increase in water demand is likely due to the rise in Blaine fineness. e water demand for samples using 25% or 33% boron compounds in the grinding aid mixture increased to 25.6 ± 0.3% compared with reference cement. e reason is again the increase in Blaine fineness of samples ground with grinding aids containing boron compounds
When boric acid (BA) is used as a grinding aid in a boron compound and TEA mixture, this would typically be expected to retard the setting points of the cement, but according to the results of this study, it decreased the retardation effect of TEA. e reason for this was due to the chemical reaction between TEA and BA so that only a small amount of TEA acted as a retarder in the hydration reactions in the cement samples

Summary

Introduction

A hydration reaction instantly starts when water is mixed with cement to form a paste that first begins to lose its plasticity and stiffens and hardens [1]. e main phases, C3A, C3S, C2S, and C4AF, react quickly with water to produce a jell-like mixture that starts solidifying. e action of changing from a fluid state to a solid state is called setting which is the transformation process from the initial state (a scattered concentrated suspension) to the final state (a connected and strengthened system of particles). A hydration reaction instantly starts when water is mixed with cement to form a paste that first begins to lose its plasticity and stiffens and hardens [1]. E action of changing from a fluid state to a solid state is called setting which is the transformation process from the initial state (a scattered concentrated suspension) to the final state (a connected and strengthened system of particles) This transformation of cement and concrete is obtained by chemical reactions between cement particles and water (i.e., cement hydration) [2]. Hardening of the cement paste (the beginning of strength gain in other words) occurs after the formation of CSH, which starts some hours after mixing. (2) Accelerating the participation of compound ions in aluminate reactions, which form aluminate ion phases mostly when there is insufficient sulfate to react with C3A. e monosulphate conversion of ettringite will not occur if free ions are available [5].

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Conclusion