# Quark Powder Valorisation in White Self-Compacting Concrete: Mortar Level Study
## 1 Introduction
GGBS can also be used in composite cement manufacture, CEM type III in the European norm EN 197-1. Currently, cement factories and concrete production industries already consume more than 90% of the available GGBS. SF is an amorphous, ultrafine powder (spherical particles) produced by silicon and ferrosilicon alloy. SF is a pozzolanic SCM used, namely, in ultra or high-performance concrete. The use of SF in concrete has several benefits well established in the scientific literature; however, it is expensive and has limited availability (1-2.5 Mt per year [9]). LF is widely used in European Construction Industry and is moderately available (300 Mt per year [9]), providing both technical, environmental and economic benefits to cement-based materials [7]. LF was used as a partial Portland clinker replacement in the 1970s, motivated by the oil crisis [12]. The LF partial cement replacement reduces the CO\({}_{2}\) emissions almost proportionally to the replacement rate because LF is not calcinated (only grounded to specific particle sizes). LF is not pozzolanic; its effect is mainly physical [13]. As such, when the water content is kept constant, the increase in the LF cement replacement ratio reduces the strength. However, previous research revealed LF might react in a hydrated cement matrix, forming secondary hydration products, calcium carbo-silicate and carbo-aluminate hydrates, and influencing the formation of CSH [14; 15; 16]. LF can also accelerate the clinker hydration reaction and provide more nucleation sites for the growth of calcium silicate hydrates [17; 18; 19; 20; 21; 22], densifying the structure of the cementitious matrix [20; 21; 22; 23; 24]. A more detailed review of the LF incorporation effect on cement-based materials is provided elsewhere [25; 26]. In Europe, though EN 197-1, composite cement type II, LF allows up to a 35% clinker PC replacement ratio. However, nowadays, fillers are often partial cement replacements during the mixing process when producing ready-mixed concrete, dry-mix mortar and concrete, among other building products. This practice was introduced in the market in the 1990s due to the advances in self-compacting concrete technology (20-40% of binder [27]). A comprehensive review of the effects of LF on various properties of SCC, in particular, is provided by [28]. The chemical and physical requirements for the limestone fillers (to be added at the mixing stage) are similar in most countries, namely, a minimum CaCO\({}_{3}\) content of 70 or 75%, and maximum contents of clay and total organic carbon. For instance, EN 197-1 requires a minimum of 75% of CaCO\({}_{3}\) in composite cement. However, from the literature survey, some waste materials or by-products are suggested to be used as filler in cement-based materials, namely, quartz powder [29; 30], dolomite [31; 32], granite powder [33; 34; 35; 36; 37] and marble powder [38; 39]. Quartz, after feldspar, is the second most abundant mineral in the earth's crust, and the chemical composition is expressed as SiO\({}_{2}\)[40]. Quartz is a unique material due to its high purity level of SiO\({}_{2}\) and its extraordinary mechanical, electrical, thermal, chemical and optical properties. Quartz adds value to various products, ranging from ceramic, glass, construction, rubber, and other high-tech industries, such as watchmaking, optics, photovoltaics, electronics, fibre optics, cosmetics and pharmaceuticals, and food. On the Mohs scale, which quantifies the hardness of minerals from 1 to 10, quartz has a degree of 7 hardness, only surpassed by topaz, Corindon (sapphires and rubies) and diamond. Quartz also stands out for its antioxidant characteristics and can present itself in a crystalline or milky appearance. Depending on particle size distribution (PSD) and specific surface, fine quartz powder may have a pozzolanic activity or only a filler effect when used in cement-based materials. However, no consensus exists on which PSD may differentiate such behaviours [41; 42].