Concrete Mix Proportion Research Articles

同一水セメント比においてスランプが異なるコンクリートの圧縮強度とヤング係数に関する一考察

This report deals with consideration in compressive strength and Young’s modulus of concrete on different slump in identical with water-cement ratio. This paper investigates mix-proportions of ready-mixed concrete, compressive strength and Young’s modulus for test piece of making production control of ready-mixed concrete. As a results, compressive strength show a tendency to get bigger when slump is bigger in identical with water-cement ratio. Young’s modulus show a tendency to get bigger when slump is smaller in identical with water-cement ratio.

Influence of Constituent Materials Properties on the Compressive Strength of in Situ Concrete in Kenya

The poor quality of Kenyan in situ concrete has necessitated research to establish the properties of the ingredient materials and their influence on the troubling rate of failure of reinforced concrete structures in the country during construction and usage. The compressive strength of concrete relies on the properties of the constituent materials, proportions of the mixture, workmanship, compaction method and curing conditions. This paper outlines findings of an experimental investigation on the properties of Kenyan concrete ingredient materials and their influence on the compressive strength of concrete in Kenya. Three types of cements (42.5N, 32.5R, 32.5N) from six different cement manufacturers and fine aggregates from three different regions in the country were used during the study. Cements and aggregates chemical analysis was done using the Atomic Absorption Spectrometer machine while the physical and the mechanical properties were checked based on the British Standards. The British DOE concrete mix design method was used to generate the concrete mix proportion and concrete was tested for early and ultimate compressive strengths at 7, 14 and 28 days. It was observed that the different cement brands have varying properties with CEM A having the highest ultimate compressive and flexural strengths. It was further noted that aggregates from the coastal region produced concrete of higher compressive strengths. When the commonly used mix design method was adopted, blended Portland cements produced concrete with ultimate compressive strengths lower than the designed target strengths. The study therefore recommends the development of a concrete mix design procedure for blended cement concrete production in Kenya.

The Effect of Concrete Mix Proportion to the Air Bubble Spacing Coefficients of Hardened Concrete

A large number of studies have shown that the air content of fresh concrete and the air bubble spacing coefficients of hardened concrete can be used to characterize the frost resistance of concrete. The performance of air-entraining agent is an important influence factor of these two indexes, and the effect of concrete mix proportion cannot be ignored. In this paper, the effect of concrete mix proportion to the air bubble spacing coefficients of hardened concrete has been studied through a series of tests.

Optimum Mix for Pervious Geopolymer Concrete (GEOCRETE) Based on Water Permeability and Compressive Strength

The production of ordinary Portland cement (OPC) consumes considerable natural resources and energy, and it also affects the emission of a significant quantity of CO 2 in the atmosphere. This pervious geopolymer concrete study aims to explore an alternative binder without OPC. Pervious geopolymer concretes were prepared from fly ash (FA), sodium silicate (NaSiO 3 ), sodium hydroxide (NaOH) solution, and coarse aggregate (CA). The effects of pervious geopolymer concrete parameters that affect water permeability and compressive strength are evaluated. The FA to CA ratios of 1:6, 1:7,1:8, and 1:9 by weight, CA sizes of 5–10, 10–14, and 14–20 mm, constant NaSiO 3 /NaOH ratio of 2.5, alkaline liquid to fly ash (AL/FA) ratios of 0.4, 0.5, and 0.6, and NaOH concentrations of 8, 10, and 12 M were the pervious geopolymer concrete mix proportions. The curing temperature of 80 °C for 24 h was used. The results showed that a pervious geopolymer concrete with CA of 10 mm achieved water permeability of 2.3 cm/s and compressive strength of 20 MPa with AL/FA ratio of 0.5, NaOH concentration of 10 M, and FA:CA of 1:7. GEOCRETE is indicated to have better engineering properties than does pervious concrete that is made of ordinary Portland cement.

Compressive Strength and Abrasion Resistance of Concretes under Varying Exposure Conditions

The purpose of this study is to comparatively evaluate the wear resistance of concretes under abrasion rates. Five concrete mix proportions of a fixed water-cement ratio of 0.45 were considered in the study, but the constituent materials, age of concrete and exposure contact conditions were varied. The coarse aggregate type employed in the study was crushed granite. The compressive strength and abrasion resistance of concretes were tested between at ages 7 to 70 days and 100 - 500 revolutions of abrasion wheels respectively. The study revealed that the compressive strength and abrasion resistance had the optimal performance when the coarse aggregate content was 45% and the worst performance when the fine aggregate content was 28.7% of the total weight of concrete constituents. There was a remarkable loss of concrete particles to wear between 200 revs and 300 revs of abrasion wheel contact. Concrete grade in excess of 60 N/mm2 is required to resist abrasion beyond 200 revolutions of abrasion wheel contact on concrete specimens. Concretes investigated also showed weak resistance to deep abrasion at and above 300 revolutions of abrasion wheel contact.

Effect of Polypropylene Fibers on Thermal and Some Mechanical Properties of No-fines Concrete

This research aims to find the optimum percentage of polypropylene fibers that can be added to no-fines concrete. The fibers added to the (1:5, 1:6, and 1:7 mix proportions) concrete with volumetric percentages of (0.1, 0.2, 0.3, 0.4, and 0.5%), together with suitable amounts of superplasticizer to keep the flow percentage at (65-75%) using constant w/c ratio of 0.4. The results indicated that the optimum volumetric percentage of the added polypropylene fibers is 0.3% which needs small amount of superplasticizer of 0.5% by cement weight, to keep its flow equivalent to the reference mix. This percentage of fibers cause an increase in compressive strength, splitting tensile strength, and modulus of rupture of 22.5, 56.1, and 67.8% respectively when using 1:5 and 1:6 of concrete mixture. But this percentage decrease when using concrete mix proportion of 1:7 to be 8.8, 23.8, and 24% respectively. Also, results indicated that concrete density and thermal conductivity didn’t affect significantly by fibers addition.

Practical technical solution for clay-contaminated sands used in concrete

Sand, whether natural or manufactured, shows in many instances varying degrees of high levels of clay contamination. This fact is encountered in different parts of the globe and can lead to serious problems in adjusting concrete mix proportions and requiring high water to cement ratios and/or high dosages of superplasticizers without necessarily meeting the workability requirements, even when the sand is previously washed with fresh water. In this paper, different types of sand from the Gulf Cooperation Council (GCC) region are being screened, analysed for their clay contents and consequent effects on plastic concrete quality. A technical solution is being proposed based on engineered superplasticizers. A testing protocol has been established to verify the robustness of optimized mix designs demonstrating the performance of the admixture in terms of initial and extended workability. In particular, it will be demonstrated that the customized concrete admixtures constitute by themselves a stand-alone answer to the usage of clay-contaminated sands in concrete.

A comparative study of chlorides and longer‐term reinforcement corrosion

High concentrations of chlorides in reinforced concretes usually are held responsible for reinforcement corrosion. However, this conflicts with many practical examples of actual concrete structures that show little reinforcement corrosion even with very high chloride concentrations. Herein a series of tests is described for reinforced concrete specimens made with fresh water, seawater, and with seawater with additional sodium chloride and exposed for 10 years in a moisture‐rich environment. All concretes retained concrete pH values well above 9, and particularly for dense high strength concretes, pH around 12. The overall amount of reinforcement corrosion was zero or almost negligible, irrespective of concrete mix proportions or concrete chloride content. These results are in strong contrast with significant corrosion reported in 1959 after only 2–3 years exposure in a parallel experiment. The difference is attributed to poor compaction of those concretes inhibiting their inability to maintain sufficiently alkaline conditions and thus protection of the reinforcing bars. Overall the present controlled experiments support practical experience that reinforced concrete structures, properly made, can survive for long periods of time in chloride‐rich environments without the occurrence of serious reinforcement corrosion.

Study of Early Age Properties and Behaviour of Concrete with GGBS as Partial Replacement of Cement

Ground granulated blast furnace slag (GGBS) is used as alternative binder material for cement in the concrete. The use of GGBS in concrete production contributes to the savings of natural resources and energy spent in cement manufacturing process and also to reduce CO 2 emissions and environmental impact. In this research, GGBS is used as binder material for Ordinary Portland Cement in concrete by replacing cement up to 45% by weight of cementitious material. This investigation is carried out to study the fresh properties, early age strength properties and mechanical properties such as compressive strength of concrete specimen by partial replacement of cement with GGBS up to 45% and compared with referral mix. A total of four concrete mix proportion (NC, Mix 1-15%, Mix 2-30%, Mix 3- 5%) with and without GGBS were made. The compression test were carried out to determine the strength properties of concrete at the age of 3 days, 7days and 28 days. The test result shows that the 28days compressive strength at 15 % GGBS content for M35 and M40 grade of concrete is comparable with referral mix. It is observed that concrete made with GGBS have lower strength at early ages, but gain strength more steadily than equivalent concrete made with Portland cement which is having higher early age strength but does not rise rapidly on the later stages. The M40 grade concrete has better workability when compared with M35 grade concrete.

Strategies for improving dimensional stability of concrete

Changes in dimension of concrete due to early-age heat generation, long-term drying shrinkage, and creep under sustained load could lead to significant movements of the concrete structure and lock-up stresses if the movements are restrained. The lock-up stresses are often large enough to cause cracking and water leakage, thereby adversely affecting the serviceability and durability of the structure. Whilst the dimensional changes are quite variable because of their dependence on the environmental conditions and applied loads, they are all related to the concrete mix proportions. Generally, the dimensional stability of concrete can be improved by reducing its cement content and paste volume. Moreover, since the aggregate also shrinks, the dimensional stability can be improved by suppressing the shrinkage of aggregate as well. In this paper, strategies for improving the dimensional stability of concrete are formulated based on experimental research. Test results are presented to demonstrate their effectiveness and applicability.

Effect on Workability of Concrete due to Partial Replacement of Natural Sand with Gold Mine Tailings

Objective: Availability of fine aggregates in its natural form is becoming very scarce. It is becoming a challenging task to meet the demand for fine aggregates in its natural form without exploiting the natural resources. To sustain the construction activity, it becomes very essential to explore the possibility of utilizing alternative materials for fine aggregates. Large quantity of inorganic industrial waste is generated annually. Coal mine wastes, blast furnaces lag, iron ore tailings, red mud, zinc tailings, goldmine tailings etc., are some of the inorganic waste products that are generated. Methods/Statistical Analysis: In this investigation, an attempt is made to replace partially naturals and with gold mine tailings and study the behavior of concrete in the green state. Mix proportion for M25 concrete was obtained as per IS: 10262 guidelines, for normal concrete and concrete containing gold mine tailings as fine aggregates. Findings: Natural fine aggregates were replaced with 10%, 20% and 30% goldmine tailings on weight basis. In all five mixes were obtained and workability studies in the form of slump and compaction factor test were carried out. The slump for normal concrete was 84.33 mm and that for concrete containing gold mine tailings was 16.33 mm. The low slump for concrete containing gold mine tailings alone may be attributed to the presence of fine particles. The slump values for 10%, 20% and 30% replacement levels are 63.6 mm, 44.33 mm and 22.6mm respectively. Similar behavior is observed in the case of compaction factor test also. The decrease in the workability of concrete may be attributed to the increase in the fineness of resulting fine aggregates. Applications/ Improvements: The application of the gold mine tailing in the high scale structures and reduce cement by GMT.

PERVIOUS CONCRETE WITH BOTTM ASH AND COPPER SLAG

Pervious concrete is a porous concrete with voids which has no fine aggregates in it thereby facilitating the drainage of rain and storm water. The interconnected porosity of the porous concrete facilitates runoff from paved areas thereby preventing water logging which causes discomfort to passengers on roads. Moreover the rough surface of the pervious concrete prevents skidding of vehicles and it has also been reported that it absorbs sound and minimizes the deposition of fine dust on the pavement surface. This type of concrete has been successfully used in pavement and parking lots. Several researchers have optimized the proportion of aggregate that can be used in pervious concrete in order to achieve maximum permeability. But as the void content increases the strength of the concrete is reduced. Pervious concrete can be designed by using little or no sand thereby proportioning the concrete to have considerable voids. The binder content is very minimum sufficient enough to just coat and bind the aggregate particles together. The coarse aggregate used can be of single gradation or gap graded to facilitate the formation of voids which are interconnected. Approximately 20 to 30% voids are present in the hardened concrete and research has shown that flow rate of 0.25 to 0.38 cm/sec can be achieved if the gradation of aggregate is designed with gap graded aggregate. The disadvantage of the pervious concrete is its low strength compared to conventional concrete. But it has been tested and reported that it has the sufficient strength that can take up the vehicle load and other loads for many other applications. This paper discusses about the suitable mix proportion for the pervious concrete that uses copper slag and bottom ash as fine aggregate and properties of the concrete in terms of strength and durability.

Mix Design Curves for High Volume Fly Ash Concrete

Concrete construction in future has to be environmental friendly apart from being safe so that society at large is benefited by the huge investments made in the infrastructure projects. To achieve this, component materials of the concrete system have to be optimized with reference to sustainability. This paper presents a study on development of mix proportions of high volume fly ash concrete (HFC). A series of HFC mixtures with cement replacement levels varying between 50% and 65% were prepared with water/binder ratios of 0.3 and 0.35. Compressive strength values were obtained at different ages. From the experimental results, pozzolanic efficiency ratios and mix design curves for HFC were established.

Effects of Concrete Mix Proportion on Electrical Resistivity of Concrete

Electrical resistivity is one of the important parameters for modeling corrosion behavior of concrete. Few researchers have been carried out to investigate this problem. This paper presents an experimental study on effects of concrete mix proportion on electrical resistivity of concrete. The electrical resistivity of concrete is measured using the four Wenner probe, which is a fast and simple test that evaluates the resistance of concrete against the entrance of ionic species. The varied parameters in this study were water/binder ratio, fly ash content, cement paste content (Υ) and curing conditions. Based on experimental results, a good correlation is obtained between electrical resistivity and compressive strength of concrete.The results showed that the electrical resistivity of concrete mainly depend on compressive strength and fly ash content. The results of this study can be used further to model the behavior of electrical resistivity of concrete when the mix proportions are provided and that can be supported information to design sacrificial anode protection system.

CO2-full factorial optimization of an ultra-high performance concrete mix design

This article presents a factorial modelling, as well as an optimization, of the mix proportion of ultra-high performance concrete (UHPC) in terms of maximising the 28-day strength and minimising CO2 emissions. A full factorial design and desirability function optimization method were performed to find the best UHPC ingredient proportions. To improve the concrete properties, the concrete performance in terms of CO2 emissions and environment effects should be considered. Ultra-high performance with superior properties requires a large amount of cement, steel fibre and an admixture; however, from an environmental perspective, cement and admixtures and steel fibre are the important matter for global warming as cement production corresponds to 5% of all the CO2 emissions around the world. In addition, the 28-day compressive strength is one of the most important properties of concrete and is related to other mechanical properties; therefore, the 28-day compressive strength and carbon oxide emissions were selected as the responses to produce the green UHPC with high performance. The mix design parameters were the cement content (C), the steel fibre amount (F), the superplasticiser (SP), the silica fume amount (SF) and the water to cementitious ratio (W/C). The variables were compared by fine aggregate mass. The optimized ingredient mix designs are valid for the mixes with .18–.32 W/C ratio, .04–.08 steel fibre, .7–1.3 cement, .15–.30 silica fume, and .04–.08 superplasticiser by fine aggregate mass.

Axial-Bending Interaction Diagrams of Reinforced Concrete Columns Exposed to Chloride Attack

This paper focuses on reinforced concrete columns load carrying capacity degradation over time due to chloride induced steel pitting corrosion. The structural element is exposed to marine environment and the effects of corrosion are described by the time degradation of the axial-bending interaction diagram. Because chlorides ingress and consequent pitting corrosion propagation are both time-dependent mechanisms, the study adopts a time-variant predictive approach to evaluate residual strength of corroded reinforced concrete columns at different lifetimes. Corrosion initiation and propagation process is modelled by taking into account all the parameters, such as external environmental conditions, concrete mix proportion, concrete cover and so on, which influence the time evolution of the corrosion phenomenon and its effects on the residual strength of RC columns.

Cost effective optimal mix proportioning of high strength self compacting concrete using response surface methodology

Optimization of the concrete mixture design is a process of search for a mixture for which the sum of the cost of the ingredients is the lowest, yet satisfying the required performance of concrete. In this study, a statistical model was carried out to model a cost effective optimal mix proportioning of high strength self-compacting concrete (HSSCC) using the Response Surface Methodology (RSM). The effect of five key mixture parameters such as water-binder ratio, cement content, fine aggregate percentage, fly ash content and superplasticizer content on the properties and performance of HSSCC like compressive strength, passing ability, segregation resistance and manufacturing cost were investigated. To demonstrate the responses of model in quadratic manner Central Composite Design (CCD) was chosen. The statistical model showed the adjusted correlation coefficient R2adj values were 92.55%, 93.49%, 92.33%, and 100% for each performance which establish the adequacy of the model. The optimum combination was determined to be 439.4 kg/m3 cement content, 35.5% W/B ratio, 50.0% fine aggregate, 49.85 kg/m3 fly ash, and 7.76 kg/m3 superplasticizer within the interest region using desirability function. Finally, it is concluded that multiobjective optimization method based on desirability function of the proposed response model offers an efficient approach regarding the HSSCC mixture optimization.

Degree of Hydration and Mass Balance Equations for Determination of Mix Proportion of Hardened OPC Concrete

A method for estimating mix proportion of hardened OPC concrete is proposed in this study. A set of mass balance equations was formed to calculate content of concrete compositions including cement, water, sand, and coarse aggregate. The degree of hydration of cement was taken into account in the analysis in order to cover the effect of age of concrete. In order to verify the accuracy of the proposed method, the determination of mix proportion of concrete was conducted on concrete specimens prepared in the laboratory with known mix proportions. Moreover, the mix proportion of concrete at different ages were calculated both with and without consideration of time-dependent degree of hydration in the analysis to clarify the enhanced capability of the proposed method when the effect of age of concrete is considered. It was found from the analytical results that the proposed method could be used to estimate mix proportion of concrete, with a satisfactory precision, at any age. The calculation of mix proportion of hardened concrete with consideration of time-dependent degree of hydration provided less error than that without consideration of the degree of hydration. The percentage of error of the mix proportion prediction of the concrete samples was less than 5%.

Fracture behaviors of concrete CSTBD specimens by the modified MTS criterion under the condition of compression loading

A group of concrete cracked straight-through Brazilian discs are investigated under the condition of quasi-static compression loading, and the fracture initiation angles and the fracture resistances of pure mode II and I-II mixed mode on concrete are obtained by changing the directions of initial cracks and concrete mix proportion. The predictive fracture resistances of different proportions and crack modes (pure mode II and I-II mixed mode) on concrete can be obtained by the modified maximum tangential stress criterion (MMTS), which is proposed by Ayatollahi et al. The predictive results from MMTS criterion are compared and analysed with those from experiments. Especially, the MMTS criterion takes into account the effects of non-singular stress terms (i.e. the T-stress, A 3 and B 3 from the expansion of Williams series and the higher order terms are ignored) in addition to the singular stress terms around the crack tip. The dimensionless parameters in the expansion of Williams series are calculated from “finite element over-deterministic” (FEOD) method. The size of the fracture process zone is calculated by using Schmidt model containing A 3 term. It is found that the results from MMTS criterion are more reliable compared to those from traditional MTS criterion or GMTS criterion when used for predicting the fracture initiation angles and the fracture resistances of pure mode II and I-II mixed mode on concrete, particularly for mode II dominant loading condition.

Strength of Laterite Rock Concrete

This paper presents the results of laboratory tests conducted to investigate a concrete made with laterite rock coarse aggregates. The structural properties considered were strength and elasticity. Laterite concrete mix proportions of 1:3:6, 1:2:4 1:1½:3 by weight of cement, river sand and laterite rock respectively at varying water/cement ratios of 0.55-0.90 were used. The results established an optimum water/cement ratio of 0.75, 0.60 and 0.55; with characteristic strengths of 12.00N/mm2,18.69N/mm2 and 22.88N/mm2 for mix 1:3:6, 1:2:4 1:1½:3 respectively. Flexural and splitting test results were about 6 - 21% of the compressive strength of the laterite rock concrete. The static modulus elasticity of laterite rock concrete is 22.72kN/mm².