Utilizing Non-Compliant Aggregates in Concrete: Addressing Chemical and Performance Challenges

The depletion of compliant aggregate resources presents a growing challenge for the concrete industry, particularly in achieving sustainable concrete production. This dissertation proposes and validates scalable strategies for incorporating non-compliant aggregates into concrete while ensuring long-term durability. Non-compliant aggregates were categorized by gradation non-conformance, deleterious chemical contamination (chlorides and sulfates), and alkali-silica reactivity (ASR), each presenting distinct durability and performance challenges.For aggregates with gradation non-compliance, optimized mix designs, coupled with admixtures, improved workability, strength, and durability, often matching or exceeding conventional concrete performance metrics. Silane surface treatment significantly increased resistivity, addressing the increased permeability commonly associated with poorly graded aggregates. While ASTM C33 helps control mixture quality, strict adherence may exclude viable aggregate sources. This study recommends performance-based specifications.For ASR-susceptible aggregates, Silane surface treatments significantly reduced ASR expansion when applied under low internal humidity. Silane aggregate pretreatment offered modest short-term benefit but failed long-term. These findings support surface treatments as a key component of performance-based ASR mitigation. Further performance gains with silane require precise application timing, enhanced thermal and alkali resistance, and complementary methods.For sulfate-contaminated aggregates, silane aggregate treatment significantly limited internal–external sulfate attack. However, it led to a 30–60% loss in strength and was ineffective against DEF. Surface-applied silane, when used after drying (IRH < 60%), effectively suppressed both DEF and sulfate attack for one year, showing promise under field conditions with intermittent saturation.For chloride-contaminated aggregates, aggregate pretreatment provided limited, inconsistent corrosion protection and failed under combined chloride–sulfate exposure. Surface treatments reduced short-term corrosion potential but degraded under prolonged immersion and high internal sulfate content. Surface sealing remains a promising corrosion mitigation strategy but requires improved thermal and chemical stability for long-term effectiveness.Collectively, these findings show that non-compliant aggregates, often dismissed due to liability and performance concerns, can be effectively utilized through optimized mix designs, targeted treatments, and performance validation. By mitigating ASR, corrosion, and sulfate attack, this work advances durability performance and promotes more sustainable, cost-effective construction with reduced reliance on scarce compliant materials.