Early Age Compressive Strength Research Articles

Investigation of strength and water permeability of sustainable high-performance concrete containing high-volume ground bottom ash blended with fly ash and nano-silica

This investigation focussed on minimizing the Portland cement usage in developing sustainable high-performance concrete (HPC) as low-carbon concrete. High-volume ground bottom ash (GBA) was utilized as cement substitution in combination with fly ash (FA) and nano-silica (NS) for producing HPC with compressive strength of 100 MPa, and various concrete mixes were examined to assess its workability, mechanical performance, water permeability, and carbon emissions. The microstructure of the materials and pastes were also analyzed with X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and Mercury Intrusion Porosimetry (MIP). GBA was used to replace Ordinary Portland Cement (OPC) at very high levels of cement replacement, ranging from 60 to 80 % by weight of binder. As ternary binders, 10 % fly ash and 2 % nano-silica (NS) by weight of binder were also used to replace GBA. The early-age compressive strength of HPC containing high-volume GBA increased by using 2 % of NS. Incorporating 10 % of FA into HPC reduced the superplasticizer requirement, enhanced workability, and exhibited slightly lower early strength. The compressive strength of HPC containing 58 % GBA, 10 % FA, and 2 % NS could be developed at 90 days was more than 110 MPa. Moreover, the investigation indicated that employing GBA in the mix represents environmental sustainability for the development of high-performance concrete.

EVALUATION OF EARLY-AGE COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE MASONRY UNITS

This paper presents the results of the experimental study on the early-age (1-day) compressive strength of geopolymer concrete masonry units (GCMU). The binder was a combination of ground granulated blast furnace slag (or simply slag) and fly ash with ratios of 3:1 and 1:1. It was activated using an alkaline solution consisting of sodium silicate and sodium hydroxide at a mass ratio of 1.5. Additional water was added to selected mixes to enhance the castability and compactability. The effect of the mix design parameters on the early-age compressive strength of GCMU was investigated. Results showed that an increase in the binder-to-aggregate ratio increased the compressive strength by up to 57%. Similarly, increasing the alkaline solution-to-binder and slag-to-fly ash ratios led to 4 and 3.5 times higher compressive strengths, respectively. Meanwhile, additional water had a negative impact on the compressive strength of GCMU, decreasing it by up to 74%. Still, it was possible to obtain a 1-day compressive strength of 36 MPa for a GCMU having a binder-to-aggregate ratio of 1:5, slag-to-fly ash ratio of 3:1, and solution-to-binder ratio of 0.4. Such results provide evidence of the ability to utilize geopolymer concrete in the field of masonry construction.

Fly ash-GGBS blended geopolymer mortar for early engineering characteristic at ambient temperature

Geopolymer concept is by using industrial waste materials which is rich in silica and alumina, then activating them with alkaline solution. An appropriate binder combination that achieves high early age strength at ambient temperature using FA is still subject required. Thus, this study has been designed in two stages which involving the paste and mortar studies. The alkaline activator as a blend of sodium hydroxide and sodium silicate solution with SS/SH ratio of 2.5, NaOH molarity of 12 M and L/B ratio of 0.43 are used for geopolymer composite. Compressive strength, water absorption and shrinkage are tested on geopolymer mortar with various level of blended combination. High volume content (60–80 %) gave a promising early age compressive strength at ambient temperature. Metakaolin gave a further strength improvement on geopolymer mortar. Overall, the finding suggested that the geopolymer with high FA content is suitable for cement-based material repair product.

Evaluation of Early-Age Compressive Strength in Winter Prefabrication: A Comparative Study

In the field of prefabrication, the timely demolding of concrete elements is crucial to prevent structural failures during panel lifting. This study investigates the early-age compressive strength of different concrete mixtures by simulating various prefabrication plant scenarios. Special attention is given to winter conditions, where concrete hydration tends to be slower, potentially compromising the minimum compressive strength requirement of 10 MPa. The first scenario (reference), set at an ambient temperature of 20 °C with raw materials at room temperature, establishes the baseline for comparison. Two alternative dispositions are explored: Scenario 2, with an external temperature of 8 °C and the water for mixing at 35 °C, and Scenario 3, with the same external temperature but utilizing a heating hood to maintain the concrete at 35 °C. The experimental results shed light on the effectiveness of different strategies in achieving the desired early-age compressive strength under winter conditions. The use of warm mixing water and heating hoods are evaluated as potential measures to counteract the hydration slowdown. The findings contribute valuable insights for optimizing prefabrication processes in cold weather, ensuring the structural integrity of precast concrete elements.

Automated estimation of early-age concrete compressive strength using EMI signature-driven deep learning technique

Concrete is a vital construction material for civil infrastructure, whose early-age compressive strength estimation plays a critical role in determining the proper time for formwork removal and the readiness of the structures for service. Electromechanical impedance (EMI) technique has been proven to be a non-destructive and effective method for monitoring concrete early strength gain. Nonetheless, such a technique heavily relies on effective frequency band selection and statistical parameter-based analysis, which may prevent the technique from a real-time operation. This study proposes an EMI signature-driven deep learning (DL) technique to enable the automated estimation of early-age concrete compressive strength. A novel DL framework called multi-scale learning residual denoising network (MLRD-Net) was developed to autonomously learn sensitive features from raw EMI signatures and ultimately estimate the compressive strength. The EMI signatures were collected during the strength development process of concrete specimens produced from two different mix designs based on strength. Two independent databases were constructed from recorded EMI signatures to test the effectiveness of the MLRD-Net. The results demonstrated the excellent performance of the proposed model with coefficients of determination exceeding 0.99 for both databases. In addition, the MLRD-Net showed superior performances over other methods in terms of prediction accuracy, noise resistance and fitness capacities, indicating its great potential for real-time and accurate estimation of the strength gain of early-age concrete.

Study on Early Age Concrete’s Compressive Strengths in Unmanaged Curing Condition Using IoT-Based Maturity Monitoring

Although accurately estimating the early age compressive strength of concrete is essential for the timely removal of formwork and the advancement of construction processes, it is challenging to estimate it in cool, cold, hot, or unmanaged conditions. Various nondestructive testing methods, including recent IoT-based techniques, have been proposed to determine the compressive strength of concrete. This study evaluates the maturity method using the wireless thermocouple sensor in assessing the early age compressive strength of concrete slabs, particularly those not subjected to watering and protection in a cool environment below 20 °C. For this purpose, wire and wireless thermocouple sensors were installed in reinforced concrete (RC) slabs, whereas wire thermocouple sensors were installed in concrete cylinders. In addition, the compressive strengths of standard-cured cylinders, field-cured cylinders, and core samples extracted from the RC slab were measured. On day 7, the maturity index (M) values for the field-cured cylinders were 7% lower than those of the standard-cured cylinders, and the M values for the RC slabs with wire and wireless sensors were 6% lower. The compressive strengths of the field-cured cylinders and core samples extracted from the RC slabs were 19% and 14% lower than those of the standard-cured cylinders, respectively. Thus, while the difference in M values was 6–7%, the difference in compressive strength was significantly higher, at 14–19%. In a cool environment without watering or protection, the difference in strength can be even greater. Consequently, a commercial IoT-based thermocouple sensor can replace conventional wire sensors and adopt to estimate early age compressive strength of concrete in unmanaged curing condition.

Optimizing geopolymer mortar for shotcrete applications by focusing on flowability and early-age mechanical characteristics

To facilitate the use of geopolymer materials in shotcrete applications, this study presents the development of a geopolymer mortar and explores its flowability and early-stage mechanical properties. Firstly, 15 groups of geopolymer mortar specimens with 3 liquid-binder ratios (0.70, 0.75 and 0.80) and 5 binder-aggregate ratios (0.225, 0.250, 0.275, 0.300 and 0.325) were developed. Secondly, the P-wave velocity, slump, early-age compressive strength and compressive strength were obtained by ultrasonic pulse velocity test, slump test and uniaxial compressive test. Thirdly, discussion on the effect of liquid-binder ratio and binder-aggregate ratio on P-wave velocity, flowability, compressive strength and early-age compressive strength of geopolymer mortar were carried out. Finally, an optimal mix proportions rang of geopolymer mortar materials that meet the requirements of wet shotcrete technology were proposed. The results show that P-wave velocity, slump, early-age compressive strength and compressive strength increase as the increasing of liquid-binder ratio. The slump, compressive strength and P-wave increase as the increasing of binder-aggregate ratio. Moreover, the optimal binder-aggregate ratios were proposed as 0.244 - 0.321, 0.228 - 0.298, and 0.209 - 0.241 for geopolymer mortar with a liquid-binder ratio of 0.70, 0.75 and 0.80, respectively. Geopolymer mortar in these mix proportions achieves compressive strengths ranging from 28.4 MPa to 41.1 MPa after curing for 1 day and 44.2 MPa to 55.4 MPa after curing for 28 days. The mix proportion of geopolymer mortar proposed in this paper can simultaneously meet the standard requirements for mechanical properties and flowability, demonstrating potential for wet shotcrete applications.

Evaluation of fresh state, rheological properties, and compressive strength performance of cementitious system with grinding aids

AbstractGrinding aids (GA) affect the fresh and hardened state properties of cement systems in addition to the economic and ecological advantages they provide. Nevertheless, there is not enough information in the literature regarding the effect of GA utilization on the rheological properties of cementitious systems. In this study, the effect of different types of GA utilization on the grinding efficiency, setting time, and physical properties of cement and rheological properties of cement paste was investigated. Besides, adsorption of the water‐reducing admixture (polycarboxylate ether [PCE]) to the cement containing GA was investigated by total organic carbon analysis. According to the results, regardless of the type of GA, while the grinding efficiency was positively affected by GA utilization in cement, the adsorption degree of PCE, some fresh and rheological properties of the mixtures were negatively affected. With the use of GA, an increase was observed in the early age compressive strength of mortar mixtures. Consequently, the properties of cementitious systems containing GA should be taken into consideration to assess GA performance in addition to the grinding efficiency.

Application of electrical resistivity for estimating compressive strength of FRC at early-ages

ABSTRACT The addition of fibers improves the ductility and compressive strength of concrete. Utilizing fiber in concrete, on the other hand, alter the electrical conductivity of concrete and that is especially important when concrete is being used in applications that electrical resistivity of concrete has been taken into account in the design process. Electrical resistivity of concrete can be measured using nondestructive testing techniques. Electrical resistivity has been proven to be in relationship with compressive strength of cementitious materials. The link between surface electrical resistivity (ER) and compressive strength (CS) of FRC at early ages has been investigated in the current study. Twenty-one distinct FRC mixtures have been cast using various fiber types, w/c ratios and fiber volume fractions. Test results have shown a strong relationship between electrical resistivity and mechanical properties of fiber reinforced concrete. A novel empirical equation has been proposed to estimate the compressive strength of early-age fiber reinforced concrete. The adequacy of this equation was determined by comparing actual and projected compressive strength values for FRC using a coefficient of variation. The early-age compressive strength of FRC was found to be reliable when the proposed equations were utilized.

Enhancing Railway Track Stabilization with Epoxy Resin and Crumb Rubber Powder-Modified Cement Asphalt Mortar.

This research investigates the quantitative impact of incorporating epoxy resin and crumb rubber powder (CRP) into cement asphalt mortar (CAM) for railway track stabilization. The study reveals significant improvements in various key parameters compared to conventional CAM. The modified CAM exhibits a 12.7% reduction in flow time, indicative of enhanced flowability, and a substantial 62.4% decrease in the mixing stability gap, demonstrating superior mixing stability. Additionally, the modified CAM displays remarkable early-age compressive strength, with increases of up to 15.3% compared to traditional CAM formulations. Importantly, the modified CAM showcases robust resistance to challenging environmental conditions, with only a 6.7% strength reduction after exposure to sulfuric acid, highlighting its acid resistance, and exceptional freeze-thaw resistance, with a mere 1.5% strength reduction after undergoing six cycles. In a mock-up test simulating real-world conditions, the modified CAM effectively prevents ballast layer settlement, underscoring its potential to enhance the durability of railway track infrastructure. These quantitative findings not only endorse the practical feasibility of epoxy resin and CRP-enhanced CAM but also suggest its potential to contribute significantly to railway track longevity, reduce maintenance expenditures, and ensure operational reliability.

Improvement of early strength of structural lighweight concrete using large volumes of Ground-Granulated Blast Furnace Slag

This paper presents the experimetal results on the influence of chemical additive, i.e. Ca(NO¬3)2, on the compressive strength of structural lighweight concrete (LWC) containing high volume ground-granulated blast-furnace slag (GGBFS). Structural LWC using 27% (by vol. of concrete mixture) fly ash hollow microspheres, also known as cenosphere (FAC) is used up to 27% by volume of concrete mixture with a density in the range from 1.600 to 1.900 kg/m3, compressive strength over 40 MPa. Achieving high early age compressive strength is difficult and challenging for lightweight concrete with high volume GGBFS. Therefore, the present study focused on the influence of Ca(NO3)2 on the strength development (under curing condition of 27 ± 2oC and relative humidity of 60 ± 5%) of structural LWC containing 50, 65 to 80% GGBFS (replacing cement content by weight). The experimental results show that the addition of Ca(NO3)2 enhanced the early-age compressive strength of structural LWC up to 11,6% and 9,0% at the age of 3, 7 days, respectively.

Influence of biochar and recycled gypsum on the strength and microstructure of conventional and sustainable cementitious composites

The need for sustainable waste management practices to mitigate climate change emphasized discovering alternatives for environmentally unfriendly materials with high carbon footprints such as ordinary Portland cement (OPC). This study examined the effect of biochar and its presoaking on the compressive strength, porosity, and microstructure of sustainable mortars containing fly ash, recycled gypsum drywall, and OPC by manufacturing and testing 270 cubic specimens, 30 mix designs, at 7, 28, and 90 days. The main roles of biochar in the matrix were to provide water and an additional surface for internal hydration, boost nucleation, and increase interlock in the cement paste. The water retention potential of biochar particles, however, could contribute to an artificial increase in the early-age compressive strength of cementitious composites (CCs) containing biochar. This strength was lessened over time as the retained water was utilized by cementitious reactions. The low strength of the biochar particles and its effect on the porosity of CCs were the primary sources of strength reduction of specimens containing biochar. The influence of biochar presoaking relied on the initial reactivity of binders. Lower initial reactivity lessened the initial water demand, increasing free water in the mixture, retained by non-soaked biochar. The highly reactive binders, however, needed extra water, which was supplied by presoaked biochar. The data also indicated the good compatibility and bond between biochar particles and the cement paste. The effect of adding biochar on the properties of CCs strongly depended on the particle size distributions of the composite constituents and biochar particles.

Synthesis of calcium silicate hydrate nanoparticles and their effect on cement hydration and compressive strength

This study aims to synthesize calcium silicate hydrate (CSH) nanoparticles at room temperature using a liquid-phase reaction method, to incorporate the synthesized material into a cement composite, and to study its hydration characteristics. The optimal amount of polycarboxylate-based dispersant, in terms of nanocrystal size and CSH particle aggregation state, was obtained using scanning electron microscopy. The concentration of the generated harmful ions during the synthesis was reduced via a cleaning procedure. The experiments confirmed that the CSH nanoparticles acted as nucleation sites. Moreover, the initial hydration calorific value and early-age compressive strength increased with the amount of CSH nanoparticles.

Effect of microcrystalline cellulose on rheology, hydration kinetics and early-age properties of Portland cement-based and alkali-activated slag-fly ash blend

The research examines the influence of microcrystalline cellulose (MCC) on the evolution of rheological behaviour, micro-structural build-up, hydration kinetics and early-age strength (up to seven days) of OPC and AAM matrices subject to dry and sealed curing. Rheological measurements show that the addition of MCC improves recoverability of viscosity and thixotropy of OPC-based matrices. While viscosities of MCC-OPC matrices increase with relatively low change in yield stress, MCC- AAM shows drastic increase in yield stress, up to 2.2 folds within 15 min, due to an increase in MCC content from 0.25% to 1%. This is attributed to gelation and swelling of MCC in NaOH. Hydration kinetics of MCC-OPC in the first 24 h is severely retarded with increase in MCC dosage (about 5.3 h for 1% MCC), while that of AAM is less sensitive to MCC dosage, attributed to rupture of hydrogen bonds in MCC after exposure to NaOH. The findings also show that addition of MCC reduces the heat evolution of AAM after seven days of hydration, due to its suppressing effect on fly ash dissolution. Early-age compressive strength of MCC-OPC reduces with increase in MCC content, registering a maximum reduction of 21% at 1% MCC dosage. Compressive strength of MCC-based AAM is less sensitive to curing conditions and the dosage of MCC than OPC-based matrices. The findings suggest that MCC can be a potential admixture for modifying rheology and hardening of OPC and AAM matrices, while providing an avenue for upcycling cotton textile and biomass wastes.

The Effect of RHA and GBFS on the Mechanical and Physical Properties of Cementitious Composites with High Early Age Compressive and Flexural Strength: Bayesian Algorithm for the Design

The Effect of RHA and GBFS on the Mechanical and Physical Properties of Cementitious Composites with High Early Age Compressive and Flexural Strength: Bayesian Algorithm for the Design

Increasing arsenic immobilization capacity of a binder prepared by arsenic-containing biohydrometallurgy waste: Effects of ferric/ferrous salts addition

The aim of this study was to improve the immobilization capacity of a binder prepared from As-containing biohydrometallurgy waste (BAW) on arsenic (As) by modifying it with ferric/ferrous salts. The study investigated the chemical fractions of As and its leaching characteristics. Results indicated that the addition of ferric/ferrous salts significantly reduced the mid acido-soluble fraction of As, resulting in decreased As leaching. Among the four ferric/ferrous salts studied, ferrous sulfate (FeS2) performed the best, with only 0.5 wt% of FeS2 achieving satisfactory results. The influence of ferric/ferrous salts on the strength development and reaction products were also investigated. Although the incorporation of ferric/ferrous salts reduced As leaching, it also decreased the early age compressive strength of BAW. Ferric salts had a more significant impact on the strength evolution. In addition, the mechanism of Fe species on As stability using density function theory calculation was explored. Results suggested that As species could be adsorbed on the surface of Fe species through strong covalent bonds. Overall, the study demonstrated that modifying BAW using ferric/ferrous salts could effectively reduce As leaching. However, the decrease in strength especially at the early ages must be taken into consideration when using this method.

Effect of sodium sulfate activation on the early age behaviour and microstructure development of hybrid cementitious systems containing Portland cement, and blast furnace slag

Alkali activation may help to increase the early strength and reduce the setting time of mixtures with high contents of supplementary cementitious materials (SCMs). In this research, the effect of sodium sulfate activator on reaction kinetics, compressive strength and pore structure of hybrid systems produced with 70 wt% ground granulated blast furnace slag (GGBFS) and 30 wt% Portland cement (PC) was determined. The setting time was shortened by adding sodium sulfate, but increasing the dose above 3 wt% did not influence it drastically. In-situ XRD measurements revealed an increasing ettringite formation within the first 2 days of hydration. A greater reaction of the GGBFS resulted in a pore refinement of the mortars studied and consequently raised the early age compressive strength. The assessment of a convenient dosage of activator was based on both technological and environmental parameters. The contribution of PC and GGBFS to compressive strength was “decoupled”.

Synthesis of sustainable one-part geopolymers for well cementing applications

This work describes the synthesis of a novel one-part granite-based geopolymer mix design for well cementing applications by screening and improving the early-age performance of the geopolymers. The dissolution rate of granite and potassium silicate (K2SiO3) is slightly enhanced when they are blended, compared to the situation when granite was mixed with alkali solution. It was revealed that the chemical composition of granite requires modification. Ground granulated blast-furnace slag (GGBFS) was incorporated up to 90% of total weight (wt.%) within the solid precursor to find out the optimum design, based on its effect on fluid-state and solid-state properties. Pumpability and strength development of the slurries were studied to establish the applicability of the mix designs. To further characterize the final products, the mineralogy and morphology of the specimens were examined. The use of GGBFS, to modify the chemical composition of the granite, reduces the pumping time significantly. Moreover, the use of GGBFS increases the density and initial consistency value of the slurry proportionally to the increase in GGBFS content. Additionally, a threshold effect was observed in the mechanical strength development. The higher the GGBFS content (up to 50 wt%), the higher the early-age compressive strength. The highest measured compressive strength for the neat rock-based geopolymer recipe was around 6 MPa within 1-day to 7-day for a mix of 47 wt% GGBFS to the solid precursor, while its optimized mix was around 12 MPa within the same period.

Experimental Study on Partial Replacement of Cement with Nano Silica

Cement is a building material made by grinding calcined limestone and clay to a fine powder, which can be mixed with water and poured to set as a solid mass. However it is expected that the use of Nano-silica in concrete improve the strength properties of concrete. Nano silica is used in concrete to enhance its properties such as compressive strength and tensile strength. When added to concrete, nano silica particles react with the calcium hydroxide to form additional calcium silicate hydrate, which helps to improve the concrete's strength. This can result in concrete with improved resistance to cracking and corrosion, and with a longer service life.An experimental objective has been carried out by replacing the cement with Nano silica by 0%, 0.5%,1.0%, 1.5%, 2.0%, 2.5% for M30 grade of concrete. The test conducted on it shows a considerable increase in early-age compressive strength and a Split Tensile strength of concrete on 7th day, 14th day and 28th day of curing. The final outcome of the project will have an overall beneficial effect on the utility of Nano-silica concrete in the field of civil engineering construction work.

Effect of diatomite on the reaction kinetics, early-age chemical shrinkage and microstructure of alkali-activated slag cements

Understanding and revealing the relationship between the early-age chemical shrinkage, reaction characteristic and microstructure of alkali-activated slag (AAS) pastes are of importance for the application of this cementitious material. This study investigates the effect of diatomite on the early-age compressive strength and the first 72-h chemical shrinkage of AAS pastes. A novel approach is proposed based on isothermal conduction calorimetry and 1H low-field nuclear magnetic resonance analyses to identify the internal correlation between chemical shrinkage and reaction situation. Results show that the early-age chemical shrinkage is dominated by the reaction process and reaction degree of AAS pastes. The incorporation of diatomite makes a great contribution to the control of chemical shrinkage even though it slightly sacrifices the development of compressive strength. This suggests the controls in the reaction process and chemical shrinkage of AAS pastes can be achieved by incorporating diatomite. The proposed approach can be used to assess chemical shrinkage of AAS, which contributes more to deeper understanding in the early-age volume change of alkali-activated cements.