Effect of Using Shell Molding Sand and Sodium Silicate Sand as Substitute Sources for Cement Raw Materials

摘要

The goal of this study focused on determining the optimal substituting percentage for producing cement fromnrecycled waste foundry sand (including shell molding sand and sodium silicate sand). Raw materials that werenused in preparing the pre-determined recipes were heated to 1,400u0002C for 6 h during the clinkerization process.nResultant clinkers were mixed with limestone to prepare the four types of cement (referred to as FEC-I, FEC-II,nFEC-III, and FEC-IV). Proposed results were compared with those of ASTM type I ordinary Portland cementn(OPC). Results demonstrate that the major components of OPC, including C3S, C2S, C3A, and C4AF, werenpresent in all clinkers. Compressive strength of the FEC pastes cured for 28 days was higher than that of the OPCnpaste. However, the compressive strengths with curing time between 28 and 90 days increased negligibly. X-rayndiffraction analyses of the hydrates of the OPC and the FEC pastes revealed that they comprised Ca(OH)2 and CS-nH gels. Signals in the 29Si magic-angle spinninguclear magnetic resonance (29Si MAS/NMR) spectra of thenFEC pastes demonstrated increases in intensity from Q1 and Q2 peaks in the hydrated pastes. The degree ofnhydration and the average length of the linear polysilicate anions in OPC pastes and the FEC pastes increasednwith time up to 90 days. This study demonstrated the feasibility and safety of utilizing waste shell molding sandn(7.6 wt.%) and sodium silicate sand (10.8 wt.%) in the cement manufacturing process.