article · Journal of Building Engineering
This research assesses the viability of recycling wastewater from ready-mixed concrete plants to produce one-part alkali-activated ground blast furnace slag and fly ash composites under ambient conditions. The binders combined blast furnace slag with up to fifty percent fly ash replacement, activated using sodium metasilicate powder. Testing focused on fresh, mechanical, microstructural, and long-term durability properties when tap water was partially or completely replaced with plant wash water. The results demonstrated that industrial wastewater either improved performance or caused no significant negative impacts compared to tap water. High compressive strengths exceeding eighty megapascals were achieved when fifty percent wastewater was combined with a higher activator dosage. Furthermore, wastewater improved the workability of fresh mixtures, refined the pore structure, decreased drying shrinkage and sorptivity, and increased resistance against freeze-thaw cycles, high temperatures, sulfate expansion, and alkali-silica reactions.
Concrete manufacturing generates vast quantities of wastewater from facility and truck washouts, contributing to water consumption and potential environmental contamination. Demonstrating that concrete wash water can directly replace clean tap water in low-carbon, cement-free composites offers a practical route to lower freshwater use in manufacturing while safely recycling industrial effluent into strong, resilient construction products.
This applied research directly targets ready-mixed concrete producers and precast composite manufacturers seeking to eliminate water disposal costs and lower virgin water intake. Because the tests were conducted under ambient curing conditions with one-part activators, the formulation appears near-market for integration into existing batching plants, provided real-world effluent variation and regulatory compliance are managed.
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Water scarcity is the world's most pressing issue, as concrete batching facilities and concrete mixer trucks produce massive amounts of wash water every day. Recycling waste water from ready-mix concrete factories' concrete washing water is critical for conserving hundreds of millions of tons of water and preventing water and soil contamination. This study examined the impact of waste washing water on the microstructural, durability, fresh, and mechanical characteristics of one-part alkali-activated ground blast furnace slag (GBFS)/fly as (FA) composites (AAC) containing partial and complete replacement of tap water under ambient conditions. GBFS was used as the main binder in the production of AAC. FA was also used as a binder at 0%, 25%, and 50% instead of GBFS. Sodium metasilicate (MS) was used as a one-part activator at two dosages 7.5% and 15% of the total binder. The fresh properties (setting time and flowability), physical properties, compressive and flexural strength (3, 7, 28, 90, and 180 days) and durability (high-temperature resistance, freeze, and thaw resistance, drying shrinkage, sorptivity, HCl and MgSO 4 resistances, NaCl effect and alkali-silica reaction) and microstructure analysis were investigated. The findings showed that the use of wastewater (WW) instead of tap water (TW) contributed positively or had no serious negative effect on the mechanical and durability properties of AAC. Compressive strength of 72.37 MPa and 81.67 MPa was gained with the inclusion of 50%WW at 7.5 and 15 %MS content respectively. The findings showed that WW improved the workability of fresh ACC containing FA, reduced dry shrinkage and sorptivity of ACC with 15%MS content, and refined the pores of hardened ACC. The results also supported that WW contributed to the decrease in expansion due to ASR and sulfate expansion. Using WW improved the high temperature and F-T resistance of ACC mixtures containing 15%MS content. • Slag/FA based AAC production from wastewater were produced. • Fresh, Mechanical, durability and microstructural properties of AAC were studied. • Transport properties of AAC were evaluated. • High temperatures, HCl, MgSO 4 , NaCl, ASR and F-T durability of AAC were studied.
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DOI: 10.1016/j.jobe.2023.107167
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