Low CO2 emission cement from alkali-activated gravel wash mud and quartzite dust

Geology Department, Trier University, Campus II (Geozentrum), Behringstraße 21, 54296 Trier, Germany

^* kukemilks@uni-trier.de

Abstract

High CO2 emissions and rising energy costs result in an increasing demand for innovative, environmentally friendly and energy-efficient construction materials. Gravel wash mud (GWM) is a widely available industrial by-product from gravel mining which may be used as an aluminosilicate source in the production of cementitious materials. In this study, GWM from Eifel in the SW Germany was used for the synthesis of alkali-activated cement. A high NaOH leachable Si and Al content and fine grain-size makes this material particularly applicable for synthesis of alkali-activated cements and geopolymers. Silicate dust from quartzite mining in Saarland is other industrial by-product used to improve the physical properties of the cement. Both materials were thermally and mechanically processed prior to chemical activation. A single-compound activator of NaOH solution was used, leading to no addition of soluble silicates. The main advantages of the new cement are zero CO₂ emissions from raw materials during calcination, comparatively low energy demand due to short grinding time, low temperature of calcination and low demand of alkali activator/no need for soluble silicates and valorisation of GWM and quartzite dust from aggregate mining. Experiments show that calcined kaolinite clay acts as a very effective binder in the cement formulation with quartzite dust. Consequently, a very small quantity of metakaolinite in the cement mixture is necessary, which allows for a reduced quantity of alkali-activator and related production costs of the cement. Consequently, the alkali-activated cement can provide an environmentally-friendly and cost-effective material for special applications with a high heat resistance or resistance to aggressive environments.