Water Cement Research Articles

Influence of Service Conditions and Mix Design on the Physical-Mechanical Properties of Roller-Compacted Concrete for Pavement.

This research focuses on the behavior of roller-compacted concrete (RCC) used in pavements, which are prone to deterioration affecting their performance. These deteriorations result from various causes, including traffic load, errors during construction, mix design, and ambient conditions. Among these, ambient conditions could lead to a marked variable impact on material behavior and durability depending on the conditions associated with each region. Accordingly, this study aims to deepen the understanding of the effect, which a broader range of ambient conditions and different mix designs have on the physical and mechanical properties of RCC. Measurements such as the amount of water vapor per kilogram of air were used to apply the findings comprehensively. The RCC analysis encompassed experimentation with different compositions, altering the cement water ratio amount, and adding a superplasticizer. The impact of curing on the materials was evaluated before subjecting them to various humidity and temperature conditions. Laboratory tests were conducted to measure performance, including moisture, shrinkage, compressive strength, and the progression of flexural fracture resistance over curing periods of up to 90 days. The results revealed a logarithmic correlation between shrinkage and ambient humidity, which is the most determining factor in performance. Mix optimization through increased cement and reduced water enhanced the tensile strength of the material. Furthermore, the curing process was confirmed to increase resistance to shrinkage, especially in the long term, establishing it as a crucial element for the structural stability of RCC, which is relatively insensitive to variations in ambient conditions.

PENGARUH PENAMBAHAN AM 78 CAIR TERHADAP KUAT TEKAN BETON FC’ 19,3 MPA DENGAN KONDISI FAKTOR AIR SEMEN TIDAK TETAP

Concrete is a mixture of cement, coarse aggregate, fine aggregate, water and with or without additional ingredients (admixture) in a certain ratio which will form fresh concrete. Many studies have been carried out to find alternative uses for construction because concrete is a very important element, considering its function as one of the structures most widely used by society. Concrete is a mixture of cement, coarse aggregate, fine aggregate, water and with or without additional ingredients (admixture) in a certain ratio which will form fresh concrete. The advantages of concrete as a construction material include having high compressive strength, being able to follow the shape of the building freely, being resistant to fire and relatively cheap maintenance costs. The aim of this research is to determine the effect of adding Liquid AM 78 on the compressive strength of concrete Fc' 19.3 MPa under conditions where the cement water factor is not constant. The method used in the research is SNI 63-2834-2000 procedures for making normal concrete mixtures. The conclusion from the test results was that the compressive strength value of standard concrete (BS) aged 28 days was 19.40 MPa which was greater than the compressive strength of the planned concrete, namely 19.30 MPa and the highest compressive strength value of concrete with the addition of AM 78 Liquid 1.0% (B .1.0) 28 days old is 20.57 MPa.

Determination of the maximum dissolution rates of the Belgian reference glasses at very alkaline pH and 30 °C

To assess the chemical durability of the Belgian reference glasses SON68, SM513, and SM539 under hyper-alkaline conditions, maximum glass dissolution rates were measured at 30 °C and pH 13.5 by performing Single-Pass Flow-Through tests with a KOH solution and a synthetic young cementitious water containing Ca (YCWCa). In both leachants, the highest dissolution rate was determined for the Al-rich glass SM539, while similar rates were found for SM513 and SON68 glasses, whose compositions are comparable. For all glasses, the dissolution rates in YCWCa were lower than in KOH due to the presence of Ca, which leads to the formation of a slightly protective calcium silicate layer. The dissolution rates in YCWCa were similar to those determined from glass monolith mass losses in static tests carried out at 30 °C in YCWCa in the presence of hardened Ordinary Portland Cement paste powder with a cement-to-glass ratio of 1.Graphical abstract

Water-soluble fluorosilane supplemented with fumed silica as admixture for producing hydrophobic concrete: Effects on cement hydration, mechanical properties and water protection properties

Hydrophobic admixtures protect concrete from water-related degradation, although they may have negative effects over cement hydration, mechanical properties and have low miscibility with water. Aiming to overcome these drawbacks, this work studies the properties of concretes containing admixtures based on a water-soluble fluoroalkylsilane and fumed silica to densify the structure. The effects of the admixture were evaluated in terms of hydrophobic, mechanical and chemical properties.The admixture decreased capillary absorption by over 70% while also increasing the internal cohesion, despite an increased porosity. Raman and XRD analysis indicated it promoted the consumption of C3S and the formation of portlandite and C–S–H gels with higher silicon content, compensating the effect of porosity on the concrete resistance. Incorporation of fumed silica in the admixture delayed the early development of hydrated phases, but after full curing promoted a more compact structure of the cement matrix, decreasing water absorption rate and improving mechanical properties.

Study on the optimisation of cement and binder content to develop a sustainable high-performance concrete

According to ACI concrete terminology, “High Performance concrete (HPC) is defined as a concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices”. It is a new generation of concrete that has been evolved recently and are well received for its exceptional performance of strength and durability. Due to these characteristics, HPC are utilized in the construction of bridges, hydropower structures, pavements, mass concrete projects etc. HPC is a cementitious composite material composed of an optimized gradation of granular constituents, a water-to-binder ratio of less than 0.3, a high percentage of discontinuous internal fiber reinforcement and HPC can hold compressive strength of more than 60 MPa. HPC considered in this study is made with high-strength steel fibers, fine sand, cement, mineral and chemical admixtures and water. The conventional mix design used for normal concrete cannot be adopted for HPC because of the high compressive strength to be achieved. The main objective is to develop a sustainable HPC mix with optimum particle packing density to achieve the desired strength with the lowest cement and binder content. As part of the investigation, the impact of different constituents of HPC such as cement content and binder content on the compressive strength were examined. Also, the optimum particle packing density of mixes with different amount of cement and binder content were studied using EMMA software. From the results it is observed that the increase in cement or binder content beyond a particular level will have minimal impact on the compressive strength.

Experimental Research on the Performance Characteristics of Grouting Slurry in a High-Ground-Temperature Environment

Grouting materials with good thermal insulation and reinforcement properties are the key factors in solving the temperature control problems of high geothermal tunnels using curtain grouting, as the existing grouting materials are unable to take into account the working performance and thermal insulation properties of high-temperature environments. In view of the above problems, this paper configures a high geothermal tunnel red-mud-based grouting material (RMGS) using red mud, carries out tests on the working performance (viscosity, setting time, and compressive strength) and thermal insulation performance (thermal conductivity and specific heat capacity) of the grouting materials at different temperatures (20, 40, 60, and 80 °C), and analyses the variation rules and micro-mechanisms of the various properties at different temperatures. The results show that the increase in temperature will accelerate the viscosity development and condensation of the grouting material and will also lead to the acceleration of the attenuation of the thermal conductivity of the three types of grouting material and the reduction in specific heat capacity. In addition, the appropriate temperature can improve the compressive strength of the material. The increase in temperature will accelerate the hydration reaction speed of the grouting material and will also lead to the development of the internal pore space of the material, which affects the macroscopic properties of the material and is the reason for the effect of the temperature on the performance of the grouting material. In terms of application, the cement slurry is suitable for grouting in a static water environment, the cement–water glass bi-liquid slurry is suitable for grouting in a dynamic water environment, and the RMGS is suitable for grouting in a high-ground-temperature environment.

Machine learning predictions for optimal cement content in sustainable concrete constructions

The designated concrete compressive strength at 28 days plays an important role in determining the quantity of cement (water to cement ratio) needed in concrete mix designs. Whilst a 28-day target is common, some structural elements receive deferred loads during construction, allowing a reduced cement content and the possibility to optimize the concrete mix to target full strength at 90 days. Machine learning techniques are used in this study to optimize the concrete mix design of structural elements that commonly receive deferred loads, e.g., foundation and pavements, targeting a 90-day full strength. Specifically, the compressive strength of concrete samples cured for 28 and 90 days are considered to estimate the cement content per m3 of concrete using Artificial Neural Network and Regression algorithms. The proposed machine learning and deep learning methods are proved to be capable of predicting the cement content with 94% and 90% accuracy, respectively. The Elastic Net algorithm shows the best performance in cement content optimization to a target 90-days compressive strength. This algorithm is hence employed to assess the carbon reduction benefits in a real case study: a typical mid-sized reinforced concrete structure is considered as a baseline to quantify the environmental benefit of optimizing the cement content for a 90-days target compressive strength. Results of the case study show that the proposed method may result in a reduction of approximately 10% in cement usage, consequently leading to a parallel reduction of about 10% in carbon emissions.

In-situ dispersion of nano-TiO2 to highly reinforce cement paste

Regardless of how good pre-dispersion of nano-TiO2 in aqueous solutions, re-aggregation rapidly occurs once it is mixed into fresh cement mixtures, limiting the nano-reinforcing efficiency for cement-based materials. In this study, an in-situ release strategy by pre-encapsulating nano-TiO2 in microscaled ice and post-dispersing into fresh cement matrix during ice-melting process was developed to highly reinforce the microstructure and properties of cement paste. Compared with the conventional dispersion strategy, a much better dispersion of nano-TiO2 (0.6 wt% by cement) was achieved using the in-situ release strategy, which not only improved the 7- and 28-day compressive strength of cement paste by 9.2% and 10.1%, respectively, but also reduced the cement hydration heat and water adsorption by 36.1% and 4.6%, respectively. In addition to this, the NO degradation efficiency of cement paste was also improved by 20% due to the larger exposed surface area of nano-TiO2 with better dispersion. These research outcomes demonstrate that the in-situ release strategy facilitates the dispersion of nano-TiO2 in cement matrix and contributes to highly reinforcing cement paste with lower hydration heat and water adsorption, strong mechanical strength and higher photocatalytic properties.

Hydrophobic treatment on hollow glass microspheres for enhancing the flowability of lightweight high-performance cementitious composites

The use of hollow glass microspheres (HGMs) in a low water-to-binder matrix generally hinders the flowability of the composite due to the high water absorption capacity of HGMs. This study investigated the feasibility of improving the flow behavior of lightweight high-performance cementitious composites (L-HPC) by adding microspheres with hydrophobic treatment. The hydrophobic HGMs were prepared with a ball milling method using low-cost stearic acid. The successfully modified hydrophobic HGMs were then used for the preparation of L-HPC. The results show that the production, including milling for 2–8 h with a 4 wt% addition of stearic acid, can convert hydrophilic HGMs into hydrophobic ones, with the water contact angle increasing from 0° to 102–154° (as a function of processing time). The diffraction peaks and phase transition latent heat results also proved the modification of the surface of HGMs with a hydrophobic coating layer. Cement hydration monitoring demonstrated that the hydrophobic HGMs hardly absorbed water and did not show significant wetting behavior during mixing. Since more water was available for cement hydration due to the hydrophobic effect of HGMs, the formation of hydration products and flowability were significantly increased. The presence of stearic acid delayed the contact time between some cement particles and water, thereby slowing down the heat release rate, resulting in the prevention of potential early cracking with the maintenance of high strength exhibition even with the enhanced flowability.

Assessment of strength development of soil stabilized with cement and nano SiO2

In consideration of the significant negative impact of ordinary Portland cement (OPC) on the environment, the use of nanomaterials as an additive to mitigate the amount of cement and enhance the physical and mechanical properties of cemented soil has been introduced. However, the existing empirical formulae to evaluate the strength of cemented soil with nano SiO2 additive are limited. This study aims to investigate the strength behavior of cemented soil with OPC and nano SiO2 additive through a series of unconfined compressive tests. The cemented soils with varying cement content (3 %, 5 %, 10 %, and 15 %) and water content (1LL, 1.2LL, and 1.5LL) were mixed with 0 %, 2 %, 4 %, 6 %, and 8 % nano SiO2. The unconfined compressive strength (UCS) of the cemented soils with nano SiO2 was measured at 7, 14, 28, and 56 days. Empirical models were developed to estimate the UCS of cemented soil with nano SiO2 additive. The results indicate that the incorporation of nano SiO2 can effectively improve the strength of cemented soil. The UCS decreases rapidly with an increase in the ratio of water to content (wc/c) values when the wc/c value is less than 7, while the trend of decreasing UCS stabilizes when it exceeds 7. The developed empirical models based on Gallavresi’s formula can predict the UCS of cemented soil with nano SiO2 at different curing ages from the early strength on Day 7. The average MAPE value at different curing ages is 7.37 % by comparing the experimental value with the calculated value from the empirical model, demonstrating that the developed model has good predictive ability.

Experimental and modelling study of the interaction of bentonite with alkaline water

Compacted bentonite is planned to be used as buffer and backfill materials for the containment of radioactive waste in underground repositories. The performance of these barriers depends on the swelling capacity of bentonite upon hydration. Prolonged interaction between bentonite and alkaline fluids from neighbouring concrete structures can impair the swelling capacity due to profound changes in the chemical composition of bentonite. The coupled hydro-chemo-mechanical behaviour of bentonite under such conditions is at present not well understood. This paper presents for the first time a combined experimental and modelling study that addresses this coupled behaviour with the aim of understanding the key mechanisms leading to swelling pressure loss. Two experiments are presented in which compacted Wyoming bentonite was saturated with either clay or cementitious water, leading to different initial swelling capacities. The samples were subsequently subject to a flow of a KOH-rich cementitious water leading to a slow but sustained decrease in swelling pressure in both tests. The main novelty is the application of a recently developed hydro-chemo-mechanical model for bentonite for interpretation of the experiments. The model accounts for the impact of montmorillonite dissolution, cation exchange reactions, and changes in salinity on the swelling capacity of bentonite. The model results show a relatively good agreement with experimental measurements and suggest that the decrease in swelling capacity of bentonite is driven primarily by an increase in potassium fraction in the interlayer water and by montmorillonite dissolution.

Effects of kaolin-modified superabsorbent polymers on mortar properties

This study investigates the impact of kaolin-modified superabsorbent polymers (SAPs) as internal curing agents on mortar properties. While SAPs have been known to mitigate the shrinkage of cement-based materials, their adverse effects on strength have limited their applicability. In this paper, the strength and shrinkage of mortars with varying SAP proportions were measured, along with an assessment of internal porosity and hydration conditions. Results indicate that kaolin-modified SAPs effectively reduce autogenous and drying shrinkages in mortars. Although modified SAPs influenced pore size distributions, resulting in reduced strength, higher content of kaolin composite strengthened the bond between SAPs and cement-based materials. This enhanced the spherical shape of SAPs and facilitated the release of internally stored water through capillary action, thereby increasing the contact area between cement slurry and water. Consequently, mortar hydration was promoted. Moreover, higher acrylamide content in modified SAPs improved alkali and Ca2+ resistance, increased the water absorption ratio, optimized the internal maintenance effect, and reduced the loss of flexural and compressive strength in mortars.

Two-phase reactive transport modeling of heterogeneous gas production in a low- and intermediate-level waste repository

Abstract. The widely proposed approach to dispose of low- and intermediate-level radioactive waste is to store it in a deep underground repository with multiple barriers. A typical gallery is filled with concrete containers accommodating cemented steel drums of waste. Inside a container, different gases may be produced by (bio)chemical reactions, which include pH-dependent anoxic corrosion of metals and the degradation of organic matter. Both reactions consume water and may lead to pressure buildup and transport of gas, both within and around the repository. In order to investigate the controlling factors of this gas production process, a coupled reactive transport model of component-based two-phase flow in the OpenGeoSys framework is adopted here. The numerical study of Huang et al. (2021) has shown that a realistic internal structure of a waste package, including the heterogeneous distribution of materials with different chemical and hydrological properties, and the exchange of mass at the boundaries are key factors that determine the evolution of the waste package. Based on the study of Huang et al. (2021), the geometric configuration of the model has been further extended to reflect the various conditions of a multi-container disposal in a gallery. In a two-dimensional setup several model scenarios have been designed and simulated to study the change in gas production rate over time in relation to water availability in various geological and waste storage setups. In this presentation, we show simulation results covering the geochemical evolution of a waste package over 500 years. It is found that the initial water content in the waste compartment only controls the gas production rate for the first 40 to 60 years. The early pressure buildup and gas release rates are largely controlled by several critical parameters, including the permeability of cement material and water availability at the boundary. The sensitivity of these parameters is currently being investigated in detail.

Experimental study on tracing the initial water–to-cement ratio of hardened concrete using petrography analysis

This study was performed to experimentally track the initial water-to-cement (w/c) ratio of hardened concrete by visualizing capillary porosity. The specific objective is to evaluate the accuracy of various image processing methods to investigate the fluorescence intensity of dyed epoxy resin infiltrated capillary pores as a way to trace the initial w/c ratio. The epoxy resin was infiltrated into cement paste, mortar, and concrete with different w/c ratios, and thin section images of those samples were prepared. The fluorescence intensities of the samples were quantitatively analyzed by applying Otsu, triangular, and mean methods to histogram data. A proportional relationship was established between the quantified fluorescence intensity and the designed w/c ratios of the paste, mortar, and concrete samples. Accuracy was validated by comparing histogram analysis with a visual analysis method, and the most suitable method for evaluating the initial w/c ratio was proposed.

Effect of Crushing Method on the Properties of Produced Recycled Concrete Aggregates

Construction and Demolition Waste (C&DW) is generated around the world and its quantity will increase in the future. Recycling has become the favored method of dealing with concrete waste but, to avoid its downcycling, it is important to develop a recycling process which is able to produce high-grade recycled concrete aggregates (RCA). To that end, studying the influence of the production process on the properties of RCA can prove to be a crucial step toward a more circular construction industry. In this study, the influence of the crushing method is investigated. Samples of five laboratory-made concretes have been crushed using the most common mechanical crushing methods (impact crusher and jaw crusher), and the particle size distribution, morphology, hardened cement paste content and water absorption of the produced RCA have been measured and analyzed. The findings indicate that the use of impact crushers results in the production of RCA possessing more spherical geometric characteristics, albeit with a broader particle size distribution and a relatively higher content of fine particles as compared to those obtained from jaw crushers. Additionally, it is observed that the employed crushing technique seemingly exerts no discernible impact on the hardened cement paste content and the water absorption in the context of the studied concretes.

Study of the strength properties and micromechanisms of nano-Al 2 O 3 -modified predisintegrated carbonaceous mudstone based on orthogonal design

This study aimed to improve the mechanical properties of predisintegrated carbonaceous mudstone (PCM) used as an embankment fill. The four factors used in the orthogonal design test were nano-Al 2 O 3 content, cement content, water content and compaction. After the tests were completed the strength characteristics and micromechanisms of PCM modified by nano-Al 2 O 3 and cement were studied using triaxial compression tests, X-ray diffraction analysis and SEM observations. The results show that the failure mode of PCM changes from bulging failure to shear failure when the nano-Al 2 O 3 and cement contents are increased. The order in which the factors affected the cohesion of PCM is cement content, nano-Al 2 O 3 content, water content and compaction. At a given cement content, the cohesion of PCM with an optimal compaction of 96% and a water content of 8% increases and then decreases with increasing nano-Al 2 O 3 content. The increase in the internal friction angle is proportional to the nano-Al 2 O 3 content when the cement content is between 0 and 4%. Controlling the nano-Al 2 O 3 and cement contents to 0.3 and 8%, respectively, results in a synergistic effect of both materials on the shear strength. Nano-Al 2 O 3 improves the cohesion and friction strength of PCM by accelerating the hydration of cement and optimizing the structure of the hydration products.

Utilization of waste marine dredged clay in preparing controlled low strength materials with polycarboxylate superplasticizer and ground granulated blast furnace slag

To solve the disposal of massive waste marine dredged clay (MDC), this study proposes a new method of utilizing it in preparing controlled low strength materials (CLSM). In which the polycarboxylate superplasticizer (PCE) and ground granulated blast furnace slag (GGBS) were used to break the current dilemma that the flowability and strength can only be guaranteed by simultaneously increasing the water content and cement content. The flowability, strength and hydration conductivity were investigated through a series of flow tests, unconfined compression strength (UCS) tests and hydraulic conductivity tests, the microstructure and mineralogical tests were performed to reveal the mechanism of PCE and GGBS accordingly. The results show that GGBS provides more active silicon and active aluminum to promote the generation of hydrated calcium silicate (CSH) and hydrated calcium silicate aluminate (CASH), leading to a higher strength and impermeability of CLSM with GGBS than CLSM with pure ordinary Portland cement (OPC). PCE disperses both MDC and PCE in the CLSM and improves flowability through electrostatic force and steric hindrance, contributing to a rapid increase of flowability under 0.4% of PCE content. Under the collaborative effects of PCE and GGBS, MDC-based CLSM achieves higher strength and flowability at relatively lower cement content and water content, which not only solves the contradiction between flowability and strength of conventional CLSM, but also offers scientific references to the broad application of solid wastes (MDC and GGBS) in CLSM preparation, which promotes the sustainable development of green construction materials significantly.

Metaheuristic artificial intelligence (AI): Mechanical properties of electronic waste concrete

The appropriate disposal of electronic waste (E-waste) is becoming a serious concern on a global scale. The purpose of present work is to establish a link between the mix design factors and mechanical strength using the metaheuristic based artificial intelligence (AI) Technique known as gene-expression-programming (GEP). The developed dataset includes several input variables i.e., the percentage of e-waste partial substitute, water to cement ratio, specimen age, water absorption and specific gravities of the aggregates, while the compressive strength (CS), flexural strength (FS) and tensile strength (STS) are used as predictive outcome. The established models were assessed using the root mean square error (RMSE), mean absolute error (MAE), objective function, and performance index as well as the regression measure known as the coefficient of correlation (R2). All strength models showed a significant correlation (R2 = 0.94), with the minimum statistical errors (MAE 2.04, RMSE 2.54), (MAE 0.36, RMSE 0.47), and (MAE 0.43, RMSE 0.54) for CS, FS and STS respectively. Furthermore, the parametric and sensitivity analyses were considered for analyzing impact of particular input variables on the performance of outcome. The established machine learning based metaheuristic models can be utilized confidently to use e-waste concrete in a variety of construction purposes.

PENGARUH PEMANFAATAN AIR EKSTRAKSI ECENG GONDOK TERHADAP KUAT TEKAN BETON K-175

This study aims to determine the compressive strength value of K-175 concrete with variations in theaddition of water hyacinth extraction water. The research method used was a laboratory experiment, bydetermining the cement water factor and the composition of the new mixture. In this study, 24 cube testobjects were made using variation of water hyacinth extrac mixtures of 1%, 3% and 5%. The results of thisstudy were the compressive strength value of the average normal K-175 concrete at the age of 14 and28days the compressive strength results were 144.3 kg/cm2 and 184.3 kg/cm2, while the compressive strengthwith variations in the addition of 1% water hyacinth extraction water was of 154.8 kg/cm2 and196.4 kg/cm2, variations in the addition of 3% water hyacinth extraction water was 164.7 kg/cm2 and212.3 kg/cm2, while for variations in the addition of 5% was 149.6 kg/cm2 and 193.4 kg/cm2. The optimumcompressive strength obtained in this study was the variation of 3% water hyacinth extracti mixture for theage for 28 days of age, which was 212.3 kg/cm2.

Study on Slurry Flow Characteristics and Diffusion Law of Superfine Cement-Based Composite Grouting Material

The soft surrounding rock of deep roadways is in the state of “micro-fracture and low permeability”. In order to solve the problem of grouting reinforcement of micro-fractures surrounding rock in deep roadways, the influence characteristics of auxiliary materials and additives on slurry flow were analyzed, and the composition and proportion of superfine cement-based composite grouting materials were determined: superfine cement accounted for 89.4%, superfine coal ash accounted for 5%, ultrafine mineral powder accounted for 5%, naphthalene water reducing agent accounted for 3~5‰, and lignin sulfonate calcium accounted for 1~3‰. The effects of water–cement ratio and water reducer content on slurry viscosity and water bleeding rate were tested by laboratory experiments. Based on the fracture characteristics of surrounding rock and the “Liu Jiacai Formula”, the influence law of fracture opening, grouting pressure and slurry viscosity on the slurry diffusion radius was analyzed. The results show that the slurry viscosity decreases with the increase of water–cement ratio and water reducer content, but the bleeding rate increases obviously with the increase of the two factors; when the water–cement ratio is 1.0 and the water reducer content is 3‰, the slurry has the advantages of “strong permeability, strong flow and low water bleeding rate”; the smaller the fracture opening is, the greater the required grouting pressure and the lower the required slurry viscosity. Aiming at the “micro-fracture zone” of surrounding rock in deep roadways, when the dynamic viscosity of the slurry is 2.0 mPa·s, the reasonable grouting pressure should be 12 MPa to meet the needs of grouting reinforcement engineering. The high-pressure grouting test of surrounding rock in the “micro-fracture zone” was successfully carried out by using the superfine cement-based composite grouting material.