Study of influence of alkaline component type on pH value and properties of alkali activated concretes containing basalt rock

Oleksandr Kovalchuk,Victoriya Zozulynets,S Semerikov,P Nechypurenko,A Striuk,H Danylchuk,S Chukharev,S Sakhno,T Vakaliuk,A Iatsyshyn,O Bondarenko,V Osadchyi,S Klimov

doi:10.1051/e3sconf/202128007001

Abstract

The paper discusses the questions of alkalinity changes in alkali activated cement-based materials at different stages of hardening. It was shown that use of alkali activated cement with dry alkaline component (“all-in-one system”) in the presence of basalt rock leads to the immediate decrease of pH value and strength drop of the material. On the other hand, using alkaline component in the form of alkaline solution provides almost normal hardening of systems. Taking into account obtained results a methodology of changes in concrete mix design was proposed. In general, for different cement systems under study pH value varies from 8.5 to 12 reflecting on the materials structure formation processes and strength gain. Shrinkage of the systems was within the ranges 0.3…0.6 mm/m at 28 days age and 0.3…0.5 mm/m for different systems. Absence of expansion witnesses about compensation of ASR results and normal structure developments processes in the material comparing to OPC.

Highlights

Nowadays a question of widening of raw materials base became very sharp [1,2], including materials for cement and concrete production [3,4,5]
During mix design of alkali activated cements alkaline solutions of sodium silicates and carbonates are using as an alkaline component
To determine limit points of alkali activated cements were studied of the cements using soluble glass (SS) with density 1250 kg/m3 with silicate modulus 2.6

Summary

Introduction

Nowadays a question of widening of raw materials base became very sharp [1,2], including materials for cement and concrete production [3,4,5]. In the body of concrete appears reactions «alkalis – active silica » (ASR) [27,28,29], leading to the formation in the hardened concrete pores new formations, exceeding volume of the pore [30,31,32] These formations further leads to the internal stresses in the concrete and may lead the increased leaching of the hardened stone and development of destructive processes [33,34,35]. At the same time, provided investigations studies mostly use of alkali activated cements by two component technology (alkaline component is in the liquid form) Such systems are effective enough, but application of this technology is complicated and far from the ideal [46, 47]. The aim of the study to investigate changes in pH value for different cement systems and to study optimal alkaline component content in the cement system

Raw materials and methods

Results and discussion

AAC type I

Conclusion