Test research on the effect of waste ceramic polishing powder on the compressive strength and chloride penetration resistance of seawater concrete

Abstract

Waste ceramic polishing powder (CPP) is a by-product created during the grinding and polishing process of the ceramic industry, which adversely affects the environment. In this research, it was used as auxiliary material to partially replace cement during the casting of the test specimens. The effect of cement substitution by 0%, 5%, 10%, 20%, 30%, 40% and 50% of the CPP with seawater and freshwater mixing on the compressive strength and resistance to chloride penetration of the concrete is compared. Moreover, the microstructure development and hydration products of both pastes are determined by different methods. Experimental results show that the compressive strength and resistance to chloride penetration of concrete samples, with the CPP and seawater mixing, is superior to that of the freshwater specimen, with the CPP mixing at the same curing time and the same CPP content. The compressive strength of both types of concrete tends to decrease with increasing content of CPP replacing cement. The compressive strength of concrete meets design requirements when the rate of cement replacement is up to 30% of CPP content when mixed with seawater, but the compressive strength of concrete meets design requirements when the rate of substitution cement reaches a maximum of 10 wt% CPP content mixed with freshwater. In contrast, the resistance to chloride penetration of both types of concrete mixed with CPP is better than that of the specimen without CPP and with the increase of cement replacement rate with CPP, the chloride resistance of concrete shows a rising trend. Under the same CPP substitution and the same curing time, the resistance of chloride penetration of concrete with freshwater mixing is lower than that of concrete mixed with seawater. In addition, the main hydration products in freshwater and seawater pastes with that CPP mixing were CH, ettringite and CSH. In particular, the component of the CPP promoted the formation of Friedel’s salt in concrete mixed with seawater. Seawater increased CH content at an early age (7 days) and decreased later (28 days). At a later age, most of the chlorides in seawater with that CPP component were immobilized by hydrocalumite, which microstructure became denser and compacted structure of concrete.