Suggested Citation:
Nassiri, Somayeh, Ali Zarei, Souvik Roy, Md Mostofa Haider (2026)

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

. Institute of Transportation Studies, University of California, Davis, Technical Memorandum UCD-ITS-RR-24-108

Abstract:

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 <115% of control, grinding/milling <5 minutes, foam index test: >0.40 mL air-entraining admixture demand, and ASR performance <50% of control with highly reactive aggregate. Based on these criteria, recommended SCMs for further evaluation include 15 biomass ash samples, a few biochar samples, 28 natural pozzolans, rock dust from asphalt plants, and minimally ground wash pond sludge from the C&DW group. Beyond next-phase concrete testing, additional actions were identified: expand rock dust sampling from more asphalt plants and estimate available supply in California, establish rock dust availability from aggregate quarries in California and neighboring states, and collect more wash pond sludge from concrete plants with supply estimates. Finally, to update Caltrans specifications, it was recommended to require ASTM C1897 testing for SCM acceptance (acceptance levels as above) and to revise ASTM C618 SAI from 75% at 7 days and28 days to 80% at 7 days and 28 days or 80% at 90 days and replace prescriptive compositional requirements for SCMs such as equivalent total and available alkalis with performance criteria such as ASR expansion evaluation.