Further Development Toward Implementation of Likely Supplementary Cementitious Materials (SCMs)

Samples from various material groups including biomass ashes, biochars, natural pozzolans, and construction and demolition waste (C&DW) were evaluated as supplementary cementitious materials (SCMs) for concrete. C&DW included rock dust (baghouse fines) from asphalt plants, rock dust from aggregate quarries, recycled concrete aggregate fines, crushed concrete aggregate fines, and concrete wash pond sludge. Characterization covered chemical and physical properties. Cementitious reactivity (pozzolanic or latent hydraulic) was measured based on ASTM C1897. Materials identified as pozzolanic reactive with equivalent total alkalis >5% or equivalent available alkalis >1.5% were further assessed for alkali-silica reactivity (ASR) by ASTM C1567 using a standard mortar with highly reactive sand and 20% cement replacement by each SCM. For SCMs that mitigated ASR expansion but did not meet Caltrans’s 0.1% limit, testing was repeated at replacement levels >20% when possible. A multicriteria approach was used to choose the materials to advance to the concrete-phase evaluation. Criteria were 7-day and 28-day strength activity index (SAI) >80% or 90-day SAI >80%, calorimetry heat release >90 J/g SCM, calcium hydroxide consumption >50 g/100 g SCM, water requirement 0.40 mL air-entraining admixture demand, and ASR performance