Studying Nano Clay Production and Its Effect on Some Characteristics of SCC

Abstract

The work aimed to prepare Nano clay (NC) from local Iraqi natural Kaolin clay, which was calcined at 700°C for 2 hours, then grinded for 40 hours using ultrafine grinding (Ball milling). Several techniques were used to characterize NC comprising particle size analyzers (PSA), specific surface areas (SSA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and Energy-Dispersive X-Ray Spectroscopy (EDX). The study was conducted by using three different ratios of NC (2%, 4%, and 6%) as partial cement replacements along with the use of quicklime (QLP) with (50,75 and 100) kg, which was prepared in the laboratory by burning Limestone at a temperature of 700 ℃ for two hours and combined QLP proportions with 4% NC. This depend on the results of fresh Nano clay tests for the self-compacting concrete mixes. Studying the effect of NC on the characteristics of SCC was performed based on three parameters. Firstly, the workability properties included the slump flow, V-funnel flow time, L-box, sieve segregation resistance, and fresh density. Secondly, the hardened properties were investigated at ages 7, 28, 56, 90 and 120 days, which include mechanical properties (compressive, splitting tensile and flexural strengths as well as modulus of elasticity), and the physical properties (Ultra Pulse Velocity (UPV), the harden density, the volume of permeable pores (Voids) and water absorption). Finally, the durability characteristics were examined, which include the effect of high-temperature treatment at (200, 400, 600, 800) °C at ages 56, 90 and 120 days, as well as resistance to sulfate attack through successive cycles of drying and wetting of 5%, 10% and 20% MgSO4 for a period of 30, 60 and 90 days and comparing the results with those of specimens stored at the same ages in ordinary curing water at ages 56, 90, and 120 days. The results revealed that the fresh properties decreased with increasing the content of NC. The hardened and durability properties gradually increased with increasing the content of NC and QLP in SCC mixtures. Furthermore, the addition of NC alone has II more significant effect on SCC specimens produced than reference SCC (SCC0) and QLP addition. The best value was obtained at SCC 6%NC. The results showed that the compressive strength of the SCC with 6% NC were higher than SCC0 by 28.5%, 23.6%, 19.5%, 19% and 18.4% at 7, 28, 56, 90 and 120 days curing ages, respectively. The splitting tensile strength values of SCC 6%NC was higher than reference SCC by about 16.8%, 17.1%, 16% and 12.4% at 28, 56, 90 and 120 days curing ages, respectively. The flexural strength of 6%NC was higher than SCC0 by about 22.6, 25.4, 27.4, 26.5% at 28, 56, 90 and 120 days, respectively. Furthermore, the modulus of elasticity of 6%NC was higher than SCC0 by about 26.1at 90 days curing ages. The SCC6% NC mixture achieved the gain maximum in compressive strength from the control mixture (SCC0) under the influence of 200 °C by 6.23%, 6.49%, 6.34%, while it achieved the loss minimum in compressive strength from the control mixture (SCC0) under the influence of 800 ℃ by 64.39%, 61.02%, and 55.8% at ages 56, 90, and 120 days, respectively. The SCC6% NC mix achieved the minimum loss in compressive strengths than its control mix (SCC0) through immersion in 5%, 10%, and 20% MgSO4 solutions for 30, 60, and 90 days. The strength loss ratio for 6% of NC mixed in SCCs at 30 days of sulfate immersion was lower than that of control mix (SCC0) by 39.43%, 31.43% and 27.1% at 5%, 10% and 20% MgSO4 respectively. At 60 days of sulfate immersion, the strength loss ratio was lower than SCC0 by 34.6%, 30% and 29.5% at 5%, 10% and 20% MgSO4 respectively. Finally, the strength loss ratio at 90 days of sulfate immersion was lower than SCC0 by 56.7%, 44.5% and 40.4 % at 5%, 10% and 20% MgSO4 respectively. Also, the combined addition of NC and QLP has noticeable values for the hardened and durability properties. Furthermore, it was found that using 4% NC with 100 kg QLP could provide satisfactory improvement to workability, hardened and durability properties.