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<p>This paper explores the dynamic nature of concrete strength and moisture loss during delayed curing for concrete grades M25 and M40. Ordinary Portland Cement (OPC) was partially substituted with three binders (30, 25, and 40 percent), namely Ordinary Portland Cement (OPC), Fly Ash, and Ground Granulated Blast Furnace Slag, to investigate the effects on moisture retention and strength development. Simulated delayed-curing conditions were applied to concrete samples to determine the effects of binder composition on compressive strength, moisture retention, and long-term strength. Ordinary Portland Cement (OPC), OPC with 25 per cent Fly Ash (FA25), and OPC with 40 per cent Ground Granulated Blast Furnace Slag (GGBS40) were used as the concrete specimens of grade M25 and M40, respectively. To mimic real-world field conditions, samples were cast in 150&#xa0;mm-diameter, 300&#xa0;mm-high cylinders and placed under a delayed-curing regime. Specimens were demoulded after 24&#xa0;h of initial curing in sealed moulds, followed by storage in a closed environment after 72&#xa0;h to prevent moisture loss during the delay period. Thereafter, all specimens were immersed in water for the remainder of the 28-day curing process. Normal consistency and initial and final setting time were determined according to IS:4031 (Part 4 and 5), and indicated that FA25 and GGBS40 binders required more water and had longer setting times than OPC, which is in agreement with the lower hydration rate and slower setting rate of these materials. The gravimetric method was used to measure moisture loss, with the core samples dried in the oven at different ages. A compressive strength test was also performed at 7, 14, and 28&#xa0;days, as required by IS standards. Data on compressive strength and moisture loss were used to determine the influence of binder type and curing delay on long-term performance, and predictive models were constructed to gain insight into strength-moisture interactions. Findings indicate that the early strength gains of the OPC-based mixes were higher, but moisture loss was greater (e.g., 4.5 percent in M25 and 3.8 percent in M40). In contrast, the Fly Ash and GGBS mixes showed slower gains in early strengths but better moisture retention (e.g., 2.1 percent in M25 and 1.8 percent in M40), and thus superior long-lasting strength gains. M25 and M40 recorded a total increase in strength of 30.3 and 34.7&#xa0;MPa in 72&#xa0;h, respectively. Fly Ash and GGBS blends had higher retention strength (i.e., 85 and 88 percent retention at 28&#xa0;days), indicating better long-term performance. The moisture-diffusion analysis showed that these mixes lose moisture more slowly, thereby improving durability. Further, a model for predicting compressive strength as a function of curing time and moisture loss was also developed, providing a good understanding of concrete behaviour in delayed-curing situations. The paper has shown the importance of binder composition in improving the strength and durability of the concrete in delayed curing conditions.</p>

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Strength and Moisture Behaviour of M25 and M40 Concrete with Supplementary Cementitious Materials: Experimental Study and Predictive Modelling under Delayed Curing

  • 期刊论文

  • 发表日期：

    2026年2月9日

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  • Anita C. Suryawanshi,
  • Sameer S. Shastri

摘要

This paper explores the dynamic nature of concrete strength and moisture loss during delayed curing for concrete grades M25 and M40. Ordinary Portland Cement (OPC) was partially substituted with three binders (30, 25, and 40 percent), namely Ordinary Portland Cement (OPC), Fly Ash, and Ground Granulated Blast Furnace Slag, to investigate the effects on moisture retention and strength development. Simulated delayed-curing conditions were applied to concrete samples to determine the effects of binder composition on compressive strength, moisture retention, and long-term strength. Ordinary Portland Cement (OPC), OPC with 25 per cent Fly Ash (FA25), and OPC with 40 per cent Ground Granulated Blast Furnace Slag (GGBS40) were used as the concrete specimens of grade M25 and M40, respectively. To mimic real-world field conditions, samples were cast in 150 mm-diameter, 300 mm-high cylinders and placed under a delayed-curing regime. Specimens were demoulded after 24 h of initial curing in sealed moulds, followed by storage in a closed environment after 72 h to prevent moisture loss during the delay period. Thereafter, all specimens were immersed in water for the remainder of the 28-day curing process. Normal consistency and initial and final setting time were determined according to IS:4031 (Part 4 and 5), and indicated that FA25 and GGBS40 binders required more water and had longer setting times than OPC, which is in agreement with the lower hydration rate and slower setting rate of these materials. The gravimetric method was used to measure moisture loss, with the core samples dried in the oven at different ages. A compressive strength test was also performed at 7, 14, and 28 days, as required by IS standards. Data on compressive strength and moisture loss were used to determine the influence of binder type and curing delay on long-term performance, and predictive models were constructed to gain insight into strength-moisture interactions. Findings indicate that the early strength gains of the OPC-based mixes were higher, but moisture loss was greater (e.g., 4.5 percent in M25 and 3.8 percent in M40). In contrast, the Fly Ash and GGBS mixes showed slower gains in early strengths but better moisture retention (e.g., 2.1 percent in M25 and 1.8 percent in M40), and thus superior long-lasting strength gains. M25 and M40 recorded a total increase in strength of 30.3 and 34.7 MPa in 72 h, respectively. Fly Ash and GGBS blends had higher retention strength (i.e., 85 and 88 percent retention at 28 days), indicating better long-term performance. The moisture-diffusion analysis showed that these mixes lose moisture more slowly, thereby improving durability. Further, a model for predicting compressive strength as a function of curing time and moisture loss was also developed, providing a good understanding of concrete behaviour in delayed-curing situations. The paper has shown the importance of binder composition in improving the strength and durability of the concrete in delayed curing conditions.