Thermo-physical, Electrical and Mechanical Characterizations of Normal and Special Concretes: A Holistic-Empirical Investigation for Pre-qualification and Quality-Control of Concrete

Abstract

Nine(9) Concrete specimens (Concrete test-materials) [comprising of 3 ‘Portland Cement Normal Concrete specimens’, 3 ‘Portland Slag Special Concrete specimens’ and 3 ‘Silica-fume Slag Special Concrete specimens’] were designed-for in accordance with ACI 211.1-91, cast in accordance with ASTM C 127 and cured for three(3) Curing-ages of 28 days, 56 days and 90 days. Each was subjected to eleven (11) Quality (Strength, Durability & Workability)-evaluation experimental-tests in accordance with the relevant ASTM, BSI and other scientifically-established standard procedures, so as to empirically determine their Thermo-physical, Electrical & Mechanical characterizations (behavioural-changes) and the various determining (influencing) factors (variables). Summarily, it was experimentally discovered that, Supplementary Cementitious Material (SCM) content and Maturity (Curing-age) significantly influenced (affected) five (5) conducted Thermo-physical characterization-tests of ‘Specific Heat Capacity (Cθ)’, ‘Thermal diffusivity (δThermal)’, ‘Thermal Conductivity (KThermal)’, ‘Dry bulk density (ρbulk dry)’ and ‘Water sorptivity (S)’ of Concrete. Also, it was observed that the five (5) conducted Electrical characterization-tests i.e. ‘RCPT Total Electric Charge passed (∑QP)’, ‘Chloride-ion Penetrability’, ‘Initial 5 minutes RCPT Electricity Resistivity (ρE(RCPT)’, ‘Chloride-ion Penetration-depth (Cl–pd)’ and ‘Non-steady state migration coefficient (DnssMC)’ of Concrete largely depended on the Water/Cement (w/c) ratio, Maturity (Curing-age) and SCM content. Furthermore, it was noticed that Mechanical characterization-test i.e. “Average Compressive-strength’ and ‘Slump’ of Concrete is primarily a function of w/c ratio, SCM content, Maturity (Curing-age) and several other factors. Consequently, it has been experimentally revealed that amongst other things, the four (4) critical determinants of Concrete quality are the Concrete’s Water/Cement (w/c) ratio, Maturity (Curing-age), Supplementary Cementitious Material (SCM) content and Bulk density.