Effect of water-cement ratio on fracture evolution and acoustic emission characteristics of grouted reinforcement bodies under increasing-amplitude fatigue loading

The disposal of coal mine solid waste has always been a challenge in the coal mining production process, and the research and development of low-cost and high-performance filling materials is a prerequisite for achieving large-scale disposal of coal mine solid waste. The effects of water-cement ratio, foaming agent dilution ratio, foam agent content, foam stabilizer content, and gypsum content on the mechanical properties, transportation characteristics, and microstructure of cement foam filling materials were studied by laboratory test methods. The optimal ratio of cement foam filling material for comprehensive performance was determined. On this basis, the mechanism of influence of fly ash content, gangue content, and gangue particle size on the mechanics, transportation characteristics, and microstructure of foam filling materials was further studied. The experimental results show that at fly ash contents below 30%, gangue content is less than 30%. The particle size of gangue is less than 0.6 mm, and the expansion ratio of coal mine solid waste foam filling material is about three times, which has good mechanical properties and transportation performance. The on-site test results show that the control effect of the surrounding rock in the goaf is good, achieving safe and efficient mining of the working face.

This study presents a progressive strength prediction model for cement paste based on the hypothesis that compressive strength is governed by the microstructural compactness of hydration products. A three-stage modeling framework was developed: (1) a semi-empirical model for pure cement paste incorporating water-to-cement ratio and paste density; (2) a density-corrected effective water-cement ratio w/ceff that accounts for the physical effects of mineral additives including fly ash, slag, and limestone powder; and (3) a hydration-informed strength model incorporating curing age and temperature through an equivalent hydration degree αte. Experimental validation using over 60 cement paste mixes demonstrated high predictive accuracy, with coefficients of determination up to 0.97. The proposed model unifies the influence of binder composition, packing density, and curing conditions into a physically interpretable and practically applicable formulation. It enables early-age strength prediction of blended cementitious systems using only routine mix and density parameters, supporting performance-based mix design and optimization. The methodology provides a robust foundation for extending compactness-based modeling to more complex cementitious materials and structural applications.

Effects of water-cement ratio and particle diameter on the mechanical properties of cement paste particles

Concrete construction is widely used by the community, for example, building construction, bridge construction, port construction, girder construction, and others that require determining the quality of concrete. The use of concrete for protected and unprotected areas differs. In general, the community uses concrete construction for road hardening and for building their homes. In general, when mixing concrete, the water used during mixing tends to be free, without important rules, making it easy to work. This will affect the quality or grade of concrete. The research on the effect of water-cement ratio (W/C) on the compressive strength of concrete from Krasak river aggregates, as the main material that is currently widely available in the Krasak River, Pabelan River, and Kali Putih River. In these places, sand with various sizes and split or crushed stone from various stone crusher companies are available. This research follows the Indonesian National Standard (SNI) on the Selection of Concrete Mixtures for Normal Concrete, Heavy Concrete, and Mass Concrete. The concrete mixing is done with a volume ratio of 1pc:2ps:2split with six variations of W/C, namely 0.37, 0.46, 0.55, 0.61, 0.64, and 0.73. The sand and split materials are tested according to SNI, namely the testing of fine aggregate and coarse aggregate materials. Mix design is performed based on the data of fine and coarse aggregates. The test objects are made by mixing materials such as cement, sand, gravel, and water. The mixing is carried out by testing the fresh concrete or slump and making cylindrical test objects and soaking them for 28 days. Then, the compressive strength of the concrete is tested. The compressive strength test results show that the W/C ratios of 0.37, 0.46, 0.55, 0.61, 0.64, and 0.73 with slump values of 0, 3, 5, 8, 14, and 18 cm produce compressive strengths of 9.90, 13.75, 14.62, 20.18, 13.50, and 6.97 kg/cm2, respectively. From the test results, it can be seen that the best W/C ratio is 0.61 with a compressive strength of 20.18 kg/cm2.

The principles of the circular economy and the effective utilization of construction and demolition waste are becoming increasingly important, as evidenced by a growing body of research in this field. However, studies focusing on the waterproofing properties and setting times of recycled concrete derived from various construction and demolition waste sources remain scarce. This research investigates the characteristics of recycled aggregates from different origins and explores how these characteristics influence the properties of concrete. The study examines the effects of pre-soaking aggregates to saturation, the incorporation of water absorption-reducing additives, and the ratio of recycled aggregates to natural aggregates on the properties of both fresh and hardened concrete. Laboratory tests were conducted on crushed recycled concrete aggregates (RCA), confirming that concrete produced with recycled aggregates can meet standard requirements for compressive strength and water resistance exposure classes despite the recycled aggregates themselves not meeting the required standards. The results were used to calculate an effective water-cement ratio and establish a correlation between this ratio and compressive strength. The findings indicated that the compressive strength of mixtures approached, and in most instances exceeded, that of the reference concrete utilizing natural aggregates. Specifically, the reference concrete (REF-1) achieved a compressive strength value of 51.4 MPa after 28 days, whereas the 30% recycled mixture (REC-10), made from pure concrete demolition waste, produced a compressive strength of 62.7 MPa. The maximum water penetration depth of the REC-10 mixture was measured at 11 mm, in comparison to 15 mm for the reference mixture (REF-1). Additionally, the initial setting time of the mixtures incorporating special additives reached the 80 min threshold. The practical aspects of this research examined potential industrial applications that do not necessitate special aggregate treatments, thus maintaining the water-cement ratio within acceptable limits. This study evaluates the feasibility of utilizing recycled concrete aggregates (RCA) from construction waste to produce concrete that satisfies the standard requirements for compressive strength and water resistance. It assesses the impact of RCA on performance, provides industrial insights, and suggests potential regulatory revisions.

Roller compacted concrete (RCC) is a durable, economical, low-maintenance material for low speed heavy duty paving applications. However, it is difficult to prepare laboratory specimens to represent field performance, because RCC is very dry and requires considerable compactive effort to achieve field densities. The gyratory compactor, commonly used to prepare hot mix asphalt specimens, may be used in preparing specimens for laboratory testing. Materials and mix designs from two industrial paving projects were used to prepare specimens for comparison. Results indicated that the gyratory compactor produced specimens with mechanical properties consistent with those achieved in the field. Specimens had high strength and consistent density, with low variability. Laboratory specimens achieved density and strength comparable with cores extracted from field test strips. The effects of water-cement ratio and degree of compaction on the freeze-thaw resistance of gyratory compacted RCC were also investigated.

Abstract. This paper reports the result of investigations on the effect of water cement ratio and delay in casting on the workability and compressive strength characteristics of laterized concrete. Three mix ratios 1:1:2, 1:1.5:3, 1:2:4 and varying fine aggregate fraction replacements of sand with laterite amounting to 0%, 25%, 50%, 75% and 100% were investigated. Test result showed that the workability increases with increasing water cement ratio and decreases with increasing period of delay of casting. The compressive strength decreases with increasing water cement ratio. Delaying the casting for up to 40 minutes for 1:1:2 mix, 30 minutes for 1:1.5:3 mix and between 15 to 25 minutes for 1:2:4 mix resulted in beneficial effects amounting averagely to 20% gain in compressive strength with no appreciable loss in workability. The use of superplasticizers to improve workability and mechanical compaction to improve strength in laterized concreting processes is recommended.

Numerical simulations study of concrete mix proportion based on fluidity

The use of biochar as a concrete constituent has been proposed to reduce the massive carbon footprint of concrete. Due to the low density and complex porosity of biochar, microstructural analysis of Portland cement-biochar composites is challenging. This causes challenges to the improvement of the micro-scale understanding of biochar composite behavior. This work advances the microstructural understanding of Portland cement composites with 0, 5, and 25 volume percent (vol%) of cement replaced with wood biochar by applying common characterization techniques of mercury intrusion porosimetry (MIP), gas sorption, scanning electron microscopy, and isothermal heat flow calorimetry (HFC) in conjunction with 1H nuclear magnetic resonance (NMR) and micro-X-ray computed tomography (XCT) analysis techniques. The combination of these techniques allows a multi-scale investigation of the effect of biochar on the microstructure of cement paste. NMR and XCT techniques allow the observation and quantification of the pore space. HFC and MIP confirmed that biochar absorbs moisture and reduces the effective water-cement ratio. Gas sorption, MIP, and NMR shows that 5 vol% replacement does not significantly affect the gel and capillary pore structures. Results from XCT (supported by MIP and NMR) show that biochar can reduce the formation of larger pores. Importantly, XCT results suggest that biochar can act as a flaw in the microstructure which could explain reductions in the mechanical properties. Overall, the mechanical properties already analyzed in the literature are consistent with the microstructural changes observed, and these results highlight the need to carefully tailor the volume fraction of biochar to control its effect on the paste microstructure.

Effect of water-cement ratio on the bond strength of cold joint foam concrete and crack evolution characteristics

It is a common problem that the soft soil solidified strength by mixing is low. In order to search for the sensitive factors that affect the solidified strength, a certain marine soft soil is taken as an object, four influencing factors, such as solidified material and its dosage, mixing uniformity, water-cement ratio and curing environment, were selected for experimental study, the results show that: (1) the effect of the curing material and its content on the curing strength is obvious: the curing agent of HR soft clay is 183-212% of the cement curing strength, and the curing strength of the same kind of curing material with 20% is 25-44% higher than that of 15%. 2 mixing uniformity has a significant effect on the curing strength: the curing strength of slurry and soft soil after mixing for 1 minute is very different, and the average strength is only 10% of the full mixing strength. The average strength of the three-minute-agitation was 49-50% of the full-agitation strength, while the average strength of the six-minute-agitation strength was 92-93% of the full-agitation strength. 3 the effect of water-cement ratio on the curing strength is obvious: the curing strength decreases by 24-47% when the water-cement ratio is 1.0 vs 0.6, and by 75-80% when the water-cement ratio is 3.0 vs 0.6. 4 curing environment has obvious influence on curing strength: compared with standard curing condition, curing strength of low temperature curing condition is reduced by 52-57%. This study has important guiding significance for soft soil foundation treatment and solidified soil based on soft soil.

Concrete, the backbone of modern infrastructure, exhibits varying mechanical behaviour that depends on its components, with aggregates playing a crucial role in its strength and durability. This study aimed to investigate the influence of elevated temperatures on the compressive strength of concrete made with different types of aggregate. A comprehensive evaluation of concrete mixes was conducted using quartz, crushed clay bricks, crushed andesite, expanded clay and expanded glass coarse aggregates. For each coarse aggregate type, concrete mixtures were made with the same amount of Portland cement, water-cement ratio, natural sand, and superplasticizer. The effective water-cement ratio and cement content were kept constant in each concrete mixture. The grading and maximum particle size were the same in all concrete mixtures. The results revealed that the type of aggregate has a significant impact on the compressive strength and thermal resistance of concrete, with andesite-containing concrete exhibiting the highest residual strength after heating up to 800 °C and clay brick-concrete displaying the highest strength under elevated temperatures up to 1000 °C. The study also found that the age of concrete affects its strength at elevated temperatures, as concrete in the early stages of hydration is more susceptible to thermal cracking than concrete that has had more time to cure. Generally, the compressive strength of normal-weight aggregates depends on the strength of the parent rock. But in the case of fire (elevated temperature), the cement paste matrix loses its strength, and the aggregates effects become more significant.

Effect of the incorporation ratio of recycled concrete aggregate on the properties of self-compacting mortar

Research on the Effects of Water-Cement Ratio and Fiber Content to the Tensile and Flexural Mechanical Properties of Eccs

Post-evaluation of frost resistance of cement concrete entities based on pore spacing factors of hardened concrete

A mix design method for self-compacting recycled aggregate concrete targeting slump-flow and compressive strength

Research on the preparation and diffusion characteristics of coal seam bottom fracture grouting material based on solid waste synergy

It is an important direction for the sustainable development of pavement to mix the discarded concrete blocks with gradation according to a certain proportion after crushing, cleaning and other technological processes, partially or completely replace aggregate, and then add cement, water, and so on to make recycled concrete for pavement paving, but the traditional evaluation model for the compressive strength (CS) of recycled concrete cannot meet the requirements of efficient calculation. To address such issues, the present research proposed to apply the firefly algorithm (FA) to optimize the random forest (RF) model. The results were demonstrated by comparing the consistency of predicted and actual values, and also by analyzing the correlation coefficient (R) and root-mean-square error (RMSE). Higher R values (0.9756 and 0.9328) and lower RMSE values (3.0752 and 6.4369) for the training and test sets present the reliability of the FA and RF hybrid machine learning model. To understand the influence law of input indexes on the output index, the importance and sensitivity of variables are further analyzed. The results displayed that effective water-cement ratio (WC) and nominal maximum recycled concrete aggregate size (NMR) have the greatest impact on the output variable, with importance scores of 2.5947 and 2.4315, respectively, while the change in the recycled concrete aggregate replacement rate (RCA) has a weak influence, with an importance score of 0.4695. Introducing FA to RF for the compressive strength modeling of recycled concrete can significantly improve the computational efficiency and accuracy.

Hydration and material properties of blended cement with ground desert sand