Effects Of Water-cement Ratio Research Articles

Effect of water-cement ratio and size on tensile damage in hardened cement paste: Insight from peridynamic simulations

This paper uses the improved bond-based peridynamics (BB PD) method to predict the crack evolution and macroscopic mechanical properties of the hardened cement paste at the micro-scale. Specifically, the prototype micro-elastic brittle (PMB) model is improved by considering an attenuation kernel function and the surface effect correction. Subsequently, the uniaxial tension simulations of hardened cement microstructures generated by μic software are systemically conducted to investigate the influences of the heterogeneity of microstructure, size effect, and water-cement ratio (w/c) on crack growth and mechanical properties, i.e., tensile strength and Young's modulus. The results show that the heterogeneity of the microstructure inevitably will cause the discreteness of the macroscopic properties of the numerical cement paste. Therefore, a statistical method is considered to analyze the mechanical properties of the hardened cement. Moreover, the tensile strength has a remarkable size effect, with the size increase of microstructure, the tensile strength decreases; the simulation results fit well with the existing analytical size effect model, i.e., Weibull size effect model, multifractal scaling law, and Bažant's size effect law. Besides, the higher ratio of w/c is likely to result in lower tensile strength, Young's modulus and premature damage to the cement paste. The predicted macroscopic mechanical properties are in good agreement with the previous simulation and experimental data, which demonstrates the reliability of the improved bond-based peridynamic method in studying the crack initiation and propagation of hardened cement paste.

Developing a model for chloride transport through concrete considering the key factors

The corrosion of chloride-induced on concrete is affected by many factors. In this research, an innovative empirical model was developed to predict the long-term chloride migration behavior in concrete, considering the effects of water-cement ratio, time, bonding effect, temperature, relative humidity, and concrete deterioration. The reliability and validity of the results evaluated by the empirical prediction model were verified by the chloride concentration data in concrete specimens exposed to the marine environment for 3, 5, and 10 years reported in the literature. Combined with the established empirical prediction model, the concrete model was regarded as a three-phase composite material composed of mortar, coarse aggregate, and interfacial transition zone. The effects of key factors on chloride migration were further analyzed by using the mesoscopic finite element numerical simulation method. It was observed that when temperature increases from 5 ℃ to 65 ℃, chloride diffusion depth rises by 3.3 times. When relative humidity increases from 20% to 100%, chloride diffusion depth rises by 4.3 times. Also, the water-cement ratio, concrete deterioration, and chloride binding effect have a non-negligible impact on chloride migration.

Monotonic and cyclic bond responses of steel bar with steel-polypropylene hybrid fiber reinforced recycled aggregate concrete

The bond failure between steel bars and concrete is the main reason for the strength degradation and deformation increase of structures in service. In this study, the bond behavior of steel bars with steel-polypropylene hybrid fiber reinforced recycled aggregate concrete (HFRAC) under monotonic and cyclic loadings was investigated. The acoustic emission (AE) technique was applied to monitor the bond response and the inner damage evolution of specimens during the loading process, and the microstructure of HFRAC was analyzed through the scanning electron microscope (SEM). The hysteresis curves, failure modes, bond strength degradation rate, and energy dissipation capacity, were systematically investigated by considering the effects of water-cement ratio, recycled aggregate replacement ratio, steel fiber volume fraction, and polypropylene fiber volume fraction. Experimental results demonstrated that there was more obvious degradation in the bond strength for the HFRAC specimens under cyclic loading, compared with that under monotonic loading. In the case of cyclic loading, the bond strength was degraded with the increase of the number of cycles, and the degradation rate increased quickly with the increase of the displacement amplitude. Moreover, the analysis of AE parameters measured on steel bar bonded recycled aggregate concrete (RAC) and HFRAC specimens, including the AE hits, AE energy, localization of AE events, and average frequency, was performed. Results showed that the AE technique could effectively monitor the bond damage of HFRAC specimens at different stages. A good correlation between the results of AE parameters analysis and the cracking process of specimens was confirmed. Based on the Weibull cumulative distribution function, the bond-slip models of steel bars with HFRAC under monotonic and cyclic loadings were proposed by considering the coupling effect of hybrid fibers and recycled coarse aggregates.

Early-age hydration characteristics of modified coal gasification slag-cement-aeolian sand paste backfill

A clear understanding of the hydration characteristics of cemented paste backfill (CPB) is helpful to analyze the reasons for the defects of low strength, large deformation and high cost in the early curing period of CPB. This is conducive to realizing the sustainable utilization of solid waste. In this paper, the hydration exothermic characteristics of MGCAPB slurry was tested. Moreover, uniaxial compressive strength(UCS) tests were carried out on the MGCAPB with curing times of 3 and 28 d. In addition, microstructure tests such as TG-DTG and SEM were performed on the MGCAPB with curing time of 3d. The hydration exothermic characteristics of MGCAPB were emphatically studied, the hydration kinetic parameters of MGCAPB were analyzed exclusively by using Krstulović-Dabić model. In addition, the mechanical properties and microscopic characteristics of MGCAPB were studied. The results shows that the hydration kinetic process of MGCAPB slurry can be described by nucleation and crystal growth (NG), phase boundary reaction (I) and diffusion (D). All the formulations of MGCAPB went through the NG-I-D stage. The process of hydration reaction was controlled by NG at the initial hydration stage, and gradually changed to process I and process D with the increase of hydration degree. Compared to the Control group, The α1 of the MGCAPB activated by the activator was high, indicating that the NG process changed to the I process only when the hydration degree was high, which was related to the effective water-cement ratio of the slurry and nucleation effect. In addition, according to the requirement(3d ≥ 0.5 MPa and 28d ≥ 1.0 MPa) that CPB can provide good roof support in a typical underground mine. In this experiment, the mechanical propertiesof all formulations met the requirements, except for the 3d UCS of the Control group(0.37 MPa) and the C-C1(0.46 MPa). Finally, TG-DTG and SEM were used to analyze the microstructures of MGCAPB with activator type and dosage. The research results can provide a new approach for intensive and comprehensive utilization of solid waste resources.

The use of olive waste for development sustainable rigid pavement concrete material

Recycle and reuse of agriculture and industrial wastes becomes a big chalenge in different parts of the world. The success in the waste recycle could lead to conserve the environment, reduce the use of cement, and improve health environment. This paper presents the potential use of fly ash from olive oil waste in Jordan to improve concrete material which could be used as a sustainable material for rigid pavement and building construction material. Olive oil ash was collected from olive oil mill and replace cement in producing concrete material. The range of cement replacement was 0% to 12.5% with increment 2.5%. The results indicate that olive oil reduces the workability of concrete material. The reduction of the slump of concrete increases with increasing olive ash content. Strength and durability of concrete improved and increased with increasing olive ash content in concrete up to 7.5 percent then the strength reduced. The results in this study show that the use of 7.5% was the optimum replacement of cement. This percent could produce concrete with higher strength and higher durability in comparison with the control concrete mix. Olive waste ash enhances both strength and durability because it reduces the effective water-cement ratio in concrete mix and filling the pore and void structure in concrete material. The benefits of this study could reduce the cost of concrete and recycle waste material and enhance concrete properties.

Effects of water-cement ratio and superplasticizer dosage on mechanical and microstructure formation of styrene-butyl acrylate copolymer concrete

The interaction between nanoparticles of Styrene-Butyl Acrylate latex and cement particles with various water-cement and superplasticizers-cement ratios during the hydration process has been investigated to achieve the best chemical combination of the materials for enhancing the mechanical properties and workability of the concrete. Analyses and experimental results have shown that the adhesive properties of Styrene Butyl Acrylate (SBA) copolymer latex along with an appropriate percentage of superplasticizers promote the performances of interlayer bonding of concrete. The compressive, splitting, and flexural strengths of specimens have been studied and the formations of the microstructures by the implementation of FESEM, EDX, XRD, FTIR, TEM, and DLS, have been analyzed. The obtained results show the considerable enhancement in the structural behavior of the copolymer-modified concrete in comparison with the control samples by creating cohesive microstructures in the presence of the copolymer. Appropriate water-cement ratio and superplasticizers were selected to study the efficient distribution of the copolymer nanoparticles throughout the cement matrix by the implementation of the FESEM and EDX analyses. The constructed polymer bridges and films between layers of Ca(OH)2 crystals have yielded to the formation of an internal cohesive strong microstructure. Also, XRD and FTIR results indicate that the stability and formation of ettringite have been enhanced by the development of calcium aluminate reaction with SBA copolymer. In the cement pore solution, the chemical interaction between nanoparticles, and Ca2+, the copolymer nanoparticles adsorption on cement paste were applied and the enhanced microstructure of the concrete was obtained.

Laboratory Study on the Effect of Water-Cement Ratio on Strength Characteristics of Jet Grouting Columns

Jet grouting is one of the most widely applied soil improvement techniques. It is suitable for most geotechnical problems, including improving bearing capacity, decreasing settlement, forming seals, and stabilizing slopes. One of the difficulties faced by designers is determining the strength and geometry of elements created using this method. Jet grouted soil-cement columns in soil are a complicated issue because they are dependent on a number of parameters such as soil type, grout and water flow rate, rotation and lifting speed of monitor, nozzle jetting force, and water to cement ratio of slurry. This paper discusses the effect of the water-cement ratio on the physical and mechanical characteristics of soilcrete. In the laboratory, sandy soil mixed with cement grout with water-cement ratio varies from (0.7:1 to 1.4:1). To evaluate the characteristics of soilcrete, 96 specimens were prepared in the laboratory and tested at different curing times. The results indicate that the Uniaxial Compressive Strength (UCS) of soilcrete decreases with increasing the (W/C) ratio of the grout, where the soilcrete strength of W/C ratio of 0.7 is higher about 237% of W/C ratio of 1.4 at 28-day; the evolution of the (UCS) is proportional to the logarithm of the curing time; the ratio between the modulus of elasticity (Etg50) to the maximum UCS varies from 113 to 175; when the water-cement ratio increases, the dry density of soilcrete decreases, as a result, the (USC) of soilcrete decreases.

Occurrence and migration laws of water in circulating fluidized bed bottom slag mortar and their influences on mortar properties

The low utilization rate of circulating fluidized bed bottom slag (CFBBS) leads to its serious stacking and induces severe environmental pollution. Fortunately, the CFBBS can be recycled to the maximum extent as aggregate in mortar or concrete. Due to the porous structure of CFBBS, the occurrence and migration of water between CFBBS and the cement paste have some special laws, which are meaningful to the applications of CFBBS in mortar or concrete. In this paper, the water occurrence and migration laws of CFBBS in pure water, fresh mortar, and hardened mortar were explored systematically. The relationships among the effective water-cement ratio, the total water-cement ratio, and the time after adding water in CFBBS mortar were discussed, and the influences of the effective water-cement ratio on the fluidity and compressive strength of mortar were studied. The strengthening mechanism of CFBBS on the interfacial transition zone (ITZ) of mortar was revealed by micro test technology. The results showed that in the fresh stage, water migrated from the cement paste to CFBBS, which reduced the effective water-cement ratio and led to the decrease of mortar fluidity and the increase of compressive strength; in the hardened stage, however, water migrated from CFBBS to the hardened paste, which maintained the internal humidity of mortar, increased the hydration degree of cement, and improved the microstructure of ITZ.

The Effect of w/c Ratio of Compacted Bored Pile to Friction Resistance of Unjani Clay

The small scale physical model of drum type was set-up to obtain the effect of water cement ratio (w/c) to pile capacity and original soil. The simulation of the process of providing bored piles model, soils model, installation and tests (pile loading tests and direct shear tests) under different water cement ratio of mortar and various moisture content of clay were done. The results reveal that the higher water content of original clay the bigger friction resistance, α value as clay soil is softer and the optimum w/c-ratio (w/c = 0,4) provides more pile capacity. It is understandable that water plays an important role, contributes to the change of surrounding clay properties. The improvement of Su ( % increase) due to compaction of concrete in bored pile, migration of moisture and reaction with surrounding clay leads to take benefit of design and construction of bored pile in clay soil for the sake of efficiency and stability.

Study on preparation and strength of high-strength micro-expansive lightweight aggregate concrete

Orthogonal design was used to research the effect of water cement ratio and the content of expansive agent and fiber on the compressive strength, bending strength and splitting strength of high-strength micro-expansive lightweight aggregate concrete. The optimum mixing proportion of lightweight concrete considering different strength target was determined through the integrated balance method. Results indicated that, the splitting strength and bending strength was about 0.04 times and 0.08∼0.12 times as big as the compressive strength when the intensity grade of lightweight concrete was LC45 or LC50. The content of ZY expansive agent has a notable influence on compressive strength, and has certain influence on bending strength. The water cement ratio and polypropylene fiber content have no significant effect on different strength target. The optimum mixing proportion for high-strength micro-expansive lightweight aggregate concrete was that, the content of ZY expansive agent and polypropylene fiber were respectively 8% and 0.1%, and water cement ratio was 0.30. The strength grade of LC50 for the optimum mixing proportion has been achieved.

Mixture design method of self-compacting lightweight aggregate concrete based on rheological property and strength of mortar

Self-compacting lightweight aggregate concrete (SCLC) is a kind of high performance concrete developed by combining the favourable properties of self-compacting concrete (SCC) and lightweight concrete (LWC). However, due to the lack of a mixture design method, its application in civil engineering is limited. Based on this, a new mixture design method taking the mortar film thickness as the key technical index was proposed. In this method, the mixture design procedure was divided into a self-compacting performance design based on the rheology of mortar and a strength design based on the effective water-cement ratio rule of mortar. By correlating the relationship between the workability and mortar rheological parameters and between strength and corresponding mortar strength, the mortar rheology and strength could be used to predict SCLC workability and strength. To verify the feasibility of this method, the self-compacting performance was designed by taking SCLC-1.8–0.35 as an example, and the strength was predicted by taking SCLC-1.8–0.3, SCLC-1.8–0.4 and related cases in the published literature as examples. This result indicated that this new design method could use the rheology and strength of mortar to predict the workability and strength of SCLC. • Mortar film thickness is the key technical index of the new mix design method. • Self-compacting performance of SCLC is designed based on mortar rheology. • Strength design of SCLC is designed based on effective water-cement ratio of mortar. • New method can predict SCLC workability and strength by using mortar properties.

Effect of Water-Cement Ratio on Mechanical Properties of Rubberized Fly Ash Concrete

One of the efforts to reduce the dependency of concrete production on natural resources along with carbon reduction is by utilizing recoverable materials as concrete constituents such as crumb rubber from scrap tires and fly ash from industrial waste. This study aims to investigate the mechanical properties of rubberized fly ash concrete which utilized crumb rubber and fly ash as a replacement for a proportion of fine aggregate and cement, respectively. Crumb rubber was used to replace 5 and 10% fine aggregate while fly ash was used to replace 10% OPC by weight. Three different water-binder (w/b) ratio, 0.55, 0.50 and 0.45, were used. The concrete specimens were prepared and tested for their density, compressive strength, splitting tensile strength, and flexural strength. Result gathered from the experimental works show a reduction in properties of rubberized concrete when compared to conventional concrete. By using a lower w/b ratio, the reduction tends to decrease and rubberized concrete with 0.45 w/b ratio recorded comparable density and strength to that normal concrete. The use of a lower water-binder ratio in concrete mix improved the strength of rubberized fly ash concrete equivalent to the normal concrete, allowing for usage of green materials in real building construction.

The effect of water cement ratio on the characteristics of multi-walled carbon nanotube reinforced concrete

Water Cement ratio play vital role in strength, durability and serviceability of concrete. In this study effect of water-cement ratio on the strength of multi walled carbon nano tube reinforced concrete is analyzed. Five concrete mixtures at different water-cement ratio (W/C) with and without carbon nano tubes (CNTs) were prepared. W/C of 0.40, 0.45, 0.48, 0.50 and 0.55 were used while quantity of carbon nano tube (CNT) was fixed at 1% by weight of cement (wbc). The workability of carbon nanotube reinforced concrete (CNTC) by was reduced by 39.57% while W/C = 0.48 was found ideal for slump as well as strength. At this W/C compressive strength for CNTC increased by 7.14%.

Investigation of carbonation resistance of recycled aggregate concrete

This paper studied the carbonation resistance of recycled aggregate concrete (RAC) designed by two mix proportion design methods through accelerated carbonation test. The investigated variables include water-cement ratio, replacement ratio of recycled coarse aggregate (RCA), and carbonation time. Based on the test results, the effects of water-cement ratio, replacement ratio of RCA, mix proportion design method, and carbonation time on the carbonation resistance of RAC were analyzed and discussed. The results showed that the mix proportion design method has a significant effect on the carbonation resistance of RAC. The replacement ratio of RCA and the water-cement ratio alternately affected the carbonation resistance of RAC. The replacement ratio of RCA is the major factor affecting the carbonation resistance of RAC. In addition, a carbonation model for RAC considering the effect of the mix proportion design method was proposed. The comparison of the test values and calculated values indicates that the proposed model can properly predict the carbonation depth of RAC.

Environmental-friendly non-sintered permeable bricks: Preparation from wrap-shell lightweight aggregates of dredged sediments and its performance

In this study, a new technology for preparation of permeable bricks from non-sintered wrap-shell lightweight aggregates (WSLAs) of dredged sediments was developed. The volume method was used to calculate the material mix ratio. The effects of water-cement ratio (W/C), forming pressure (Pf), target porosity (P) and size of aggregate particles on the compressive strength and water permeability coefficient of dredged sediment permeable bricks (DSPB) were discussed. Furthermore, the mechanism of water permeability of DSPB was deeply explored. The mass loss rate and strength loss rate of DSPB after 25 freeze–thaw cycles were compared with that of the crushed stone permeable bricks (CSAPB), the commercial sintered clay permeable bricks (SCLPB), and the commercial sintered ceramic permeable bricks (SCEPB) prepared by the same process. The damage mechanism of DSPB caused by the freeze–thaw cycles was analyzed. Results showed that when W/C was 0.34, Pf was 3 MPa, and P was 15%, the comprehensive performance of fine aggregate permeable brick (DSPB-F) was satisfactory. It was found that the water permeability coefficient of DSPB is almost proportional to the connected porosity. After 25 freeze–thaw cycles, interestingly, 0it was found that the freezing resistance of DSPB is closely related to the number, width and development trend of micro-pores and cracks at the junctions of WSLAs.

INFLUENCE OF WATER-CEMENT RATIO AND WATER REDUCING ADMIXTURES ON THE REBOUND NUMBER OF HARDENED CONCRETE

In this paper, effect of water-cement ratio (w/c) and type of water reducing admixtures (WRA) on the Schmidt hammer rebound number (RN) were investigated. Concrete of mix ratio 1:2:4 was prepared at the w/c of 0.45, 0.50, 0.55 and 0.60 and with each of the three WRA at the w/c of 0.45. Concrete cubes of size 150 mm were cast and cured in water for 3, 7 and 28 days. RNs of the cubes were determined and the compressive strengths (fc) corresponding to the RNs obtained from the conversion graph supplied by the manufacturer were compared with the compressive strengths obtained from crushing machine (CM). The results showed that as the w/c increased, the RN increased up to when w/c was 0.5 and began to drop, while there was no significant effect of all the WRA on the RN. It was also found that fc obtained from CM and those obtained using the conversion graph differed considerably. A new correlation graph was therefore proposed, which showed a correlation coefficient of 0.96, while coefficient of determination obtained for the regression equation between RN and fc, was as high as 0.92. The study concluded that w/c had effect on RN and that the equation developed could be used to determine fc, once RN is known.

The effect of water cement ratio (WCR) on compressive strength of interlocking bricks with mix design variations

Interlocking brick is a material used for wall work in home construction. Called Interlocking Brick or Brick Interlock because the method of arranging the bricks is interlocked with one another. This interlocking brick itself began to be known in Aceh Province after the 2004 tsunami disaster. Interlocking brick is a block of compacted soil, made of cement, silt soil, and dried sand, measuring 300 χ 150 χ 100 cm3. Interlocking brick can function as a wall that can withstand structural and non-structural components. The purpose of this research is to get the compressive strength value of interlocking bricks designed with variations in the water cement ratio (WCR) so that the optimum compressive strength of interlocking bricks is obtained. The WCR used was 0.3; 0.4; and 0.5, while for the composition of cement, silt, and sand the ratio of 1:2:2 is used. The making of test specimens for testing the compressive strength of interlocking bricks is by cutting the interlocking bricks into cubes measuring 50 χ 50 χ 50 mm by 5 specimens for each variation so that the total of the total specimens are 45 specimens. Testing is done at the age of 7, 14, and 28 days. The results of the compressive strength of interlocking bricks using WCR 0.3 average compressive strength at the age of 7 days reached 8.10 MPa, 14 days reached 9.49 MPa and 28 days reached 10.94 MPa. For WCR 0.4, compressive strength on average at 7 days reaches 5.69 MPa, 14 days reaches 7.61 MPa and 28 days reaches 9.77 MPa. And for WCR 0.5 the average compressive strength at the age of 7 days reaches 5.36 MPa, 14 days reaches 8.25 MPa and 28 days reaches 9.93 MPa. From the compressive strength test results the interlocking brick with a WCR variation of 0.3; 0.4; and 0.5 with a mixture of 1:2:2 can be used as wall work material in house construction for structural construction and the optimum compressive strength value is obtained at WCR 0.3.

Effect of Water-Cement Ratio on Mix Design and Mechanical Strength of Copper Slag Aggregate Concrete

In concrete, the distinct influence on most or the entirety of the properties is the measure of water utilised in the matrix. In concrete mix design, the water-cement ratio is responsible for binding all constituents of concrete together. If the water-cement proportion is higher, it brings about wider spacing between the cement aggregates and thus, influences the compaction. Correspondingly, concrete’s durability and compressive strength are decreased due to increased dampness levels. Especially with added fine aggregates the water demand increases because of the increased surface area of concrete which prompts a higher water-cement ratio. Wider spaces are formed between the aggregate materials with the addition of extra water and when the moisture vaporises, voids are filled up with air. The subsequent insufficient compaction lessens the concrete’s strength. Sets of basic experimental investigations were conducted to examine the impact of various water-cement proportion on mix design and mechanical strength of concrete incorporated with fine aggregate in terms of copper slag. Natural sand replaced with copper slag with four different percentage and correlation coefficients between mechanical properties of copper slag concrete were also evaluated.

ASSESSMENT OF THE RELIABILITY OF THE REINFORCED CONCRETE LAYER IN STRUCTURES

An urgency to use probability-based methods and probabilistic reliability indices in long-term quality assessments and predictions of reinforced concrete products and structures is under consideration. Carbonation nature and depth of protective concrete covers of reinforcement bars and stirrups are analysed. Effect of water-cement ratio on the carbonation rate of protective concrete covers is discussed. Analyzes of reliability of structures reinforcement with composite as spiral (transverse) usage and influence. Presented applied equations and the calculation example demonstrate a simplicity and necessities of probability-based methods.

Effects of water-cement ratio and notches to the flexural strength of concrete

It is often assumed that flexural strength of concrete has less significance impact on overall concrete strength. However, from fracture mechanics point-of-view tensile is an element the mechanics always look into due to cracking does associate with tension. In the research, fracture is translated into physical laboratory experiment by introducing notches. Physical laboratory works on concrete beams with three-point bend test configuration under static load and calculating outputs from laboratory with numerical equations. Three-point bend test method is conducted because from the testing, tensile strength or also recognised as flexural strength of concrete for each water-cement ratio could be attain. Thus, the aim of this article is to reveal and discuss the pattern of flexural strength of concrete on different water-cement ratio. The testing follows conventional fracture three-point bend test on concrete but with revised version by testing notched concrete beams. Normal three-point bend tests were run on concrete beams with different notch sizes; 30 mm, 15mm, and 5 mm respectively. There were three water-cement ratio decided in concrete mix; 0.3, 0.4, and 0.5. Thus, the trend of flexural strength of concrete follows the trend of water-cement ratio. Flexural strength increases when water-cement ratio increases up to water-cement ratio 0.5.