Concrete Mix Proportion Research Articles

RELIABILITY BASED MULTI-OBJECTIVE OPTIMIZATION OF CONCRETE MIX PARAMETERS USING NSGA II

This article presents a method to optimize concrete mix proportions with respect to different goals of economy and reliability or, equivalently, probability of failure. This method is based on a quadratic generalized ridge regression model to predict compressive strength of concrete for 28 days curing period and a linear regression model to predict cost of concrete. NSGA II is used to obtain reliable Pareto-optimal fronts with non-dominated solutions for different compressive strength requirements. Pareto-optimal fronts evolved by varying compressive strength requirements and probability of failure are analyzed. It is found that there is a nominal rise in cost as probability of failure decreases up to a certain limit for a given compressive strength requirement. However, there is a sharp rise in cost of concrete below that limit.

Reliable Neural Networks for Proportioning of Concrete Mixes Containing Cement Replacement Materials

Abstract Artificial neural network (ANN) is one of the most suitable analytical methods used for modeling complex relationships between concrete properties and concrete mix ingredients. In the present study, common ANN is first trained to predict concrete mix proportions using experimental data sets. Experimental data sets include the content of water, cementitious materials (cement, silica fume, rice husk ash, and natural pozzolanas), coarse and fine aggregates, superplasticizer and the compressive strength, the slump, and the maximum size of the aggregates. Also, statistical analyses are used to correlate the results and the acceptable error. Then, the neural network is retrained using experimental data sets together with analytical data sets that are produced using the Iranian national concrete mix design method, empirical relationships, or both. Finally, the performance of the retrained neural networks is compared with the first one. The results show that the neural networks, which are trained using both analytical and experimental data sets, are more reliable and can be reliably used for modeling of complex relationships.

Numerical Analysis of Mix Proportion of Self-Compacting Concrete Compared to Ordinary Concrete

Steel fiber reinforced concrete (SFRC) is developed traditionally from ordinary concreteadmixed with randomly distributed steel fibers. The matrix of SFRC is always formed by adjustingthe mix proportion used for the ordinary concrete, which plays the role of controlling the properties ofSFRC. In this paper, the mix proportion of self-compacting concrete (SCC) compared with vibrationcompacted concrete (VCC) is statistically analyzed. A predictive formula for water-binder ratio isproposed in relation to the designed compressive strength of SCC and the cement strength affected bymineral admixtures. It is expected to provide reference for the mix proportion design for flowing andhigh-flowing SFRC.

Characterization of palm oil fuel ash and eggshell powder as partial cement replacement in concrete

The utilization of palm oil fuel ash (POFA) and eggshell powder (ESP) in concrete as a cement replacement is possible as green concrete materials. However, the POFA has original cellulose and physical modification is needed. This paper presents the characterization of POFA; unground POFA (UPOFA) and ground POFA(GPOFA) and ESP under microstructure examination includes x-ray fluorescence (XRF), scanning electron microscopy (SEM), and particle size analyzer (PSA). Then, the POFA-ESP as a cement replacement in concrete was investigated. Optimum mix proportion of POFA-ESP concrete was determined from compression test and GPOFA-ESP and UPOFA-ESP were through further investigation on pozzolanic reaction under x-ray diffraction (XRD) test at 14 days-concrete age. It was found that the combination of GPOFA-ESP as a cement replacement produced a concrete enhanced the compressive strength than normal concrete. ESP in this study seems like a catalyst which acting as mild accelerator or booster to improve the early age of strength development without disturb the later strength development of concrete. In addition, combination of GPOFA-ESP could increase the C-S-H gel at early age of concrete. It can be concluded that the combination of GPOFA-ESP had dual function; ESP and GPOFA took at early and later strength development, respectively.

Influence of coupled effects between flexural tensile stress and carbonation time on the carbonation depth of concrete

Concrete stress has a great influence on the depth of carbonation, thus it is of vital importance to investigate the carbonation depth model under concrete stress state. Generally, the concrete structure has time-dependent characteristics, since as concrete ages, its strength, stiffness and other properties will also change. Therefore, under the same concrete stress and different carbonation time, the influence of concrete stress on carbonation depth will be different. To investigate the influence of the coupled effects between flexural tensile stress and carbonation time on the carbonation depth of concrete, a model of stress influence coefficient considering the influence of carbonation time was established by using the existing experimental data, and a modified carbonation depth model of concrete was proposed. Results indicated that the carbonation depth increased with an increase in flexural tensile stress level. As carbonation time increased under the same flexural tensile stress level, the stress influence coefficient decreased, and the computed results of the model of stress influence coefficient considering carbonation time were in good agreement with the experimental data. The maximum influence of the mix proportions of concrete on stress influence coefficient was limited, which was approximately within ±10%. The modified carbonation depth model was reasonable and had high prediction accuracy.

A Review Paper on Specimens Size and Shape Effects on the Concrete Properties

Concrete properties are the most essential and critical physical material property when reinforced concrete structures are planned. Because of the development and in types and nature of material used to enhance the concrete innovation, materials and mix proportions, test measure, mixing strategy, and testing condition have noteworthy impacts on highlights of concrete strength, in light of the fact that the control specimen sizes and shapes might be unique in relation from State to State. Testing of mechanical properties (especially compressive strength and tensile strength) of concrete is one of the most urgent stages of development. To control the nature of the concrete, there are different molds used for pouring concrete samples according to different directions in different countries. Many researchers have realized that the specific shapes and sizes of concrete samples can cause different types in the consequences of compressive strength or tensile strength. The relationship between the compressive strength of the concrete cube and the cylinder is complex. The cylinder and concrete cube samples were compared in the pressure test by studying previous research, including the test methodology, factors affecting the cylinder / cube strength ratio, and the coefficients, equations and components of the conversion factors. Previous attempts to determine experimental transformational relationships and conversion factors have proved that it is disturbing (if not impossible) to predict the relationships between the forces of the cylinder and the cube. Previous research has shown that the ratio of the strength of the cylinder / cube is between 0.65 and 0.90, despite the fact that the ratios outside this range have been found similarly. In light of this review of previous research, the test of the cylinder is not initiated by testing the cube. This study is a review of the sample size and shape effect on concrete properties.

Utilisation of water quenched slag as fine aggregate in alkali activated mortar

This study investigates the performance of water-quenched slag (WQS) fine aggregate in blended ground granulated blast furnace slag (GGBFS) and fly ash (FA) alkali-activated materials (AAM). Mortar samples derived from the corresponding concrete mix proportion were synthesised in this study, where river sand and WQS constituted the fine aggregate system in different proportions. Analysis of workability, rheological properties, mechanical properties, shrinkage, and microstructure were carried out. The results showed that the workability of AAM, setting time, and flowability deteriorated with an increase in WQS aggregate. AAM samples witnessed higher viscosity with increasing WQS, and a certain amount of WQS added bonds and mechanical force between particles to make mortars flow at a suitable rate. Shrinkage testing included both autogenous shrinkage during the first three days and drying shrinkage during the following 360 days. WQS had an effect on shrinkage due to physical properties such as irregular grain shape and rough surface, however, high shrinkage was also attributed to pore structures. Although WQS is conducive to improvement of microstructures, too much WQS as fine aggregate in AAM deteriorates the microstructures.

Mix proportioning of M80 grade Self-Compacting Concrete based on Nan Su Mix design method principles

The quest for the development of high strength and high performance concretes has increased considerably in recent times because of the demands from the construction industry. High-performance concretes can be produced at lower water/powder ratios by incorporating these supplementary materials. Fly ash addition proves most economical among these choices, even though addition of fly ash may lead to slower concrete hardening. However, when high strength is desired, use of silica fume is more useful. This paper proposes a mix proportions for M80 grade Self-compacting concrete (SCC) based on Nan Su mix design principles. First, the amount of aggregates required is determined, and the paste of binders is then filled into the voids of aggregates to ensure that the concrete thus obtained has flowability, self-compacting ability and other desired SCC properties. The amount of aggregates, binders and mixing water, as well as type and dosage of superplasticizer (SP) to be used are the major factors influencing the properties of SCC. Slump flow, V-funnel, L-flow, U-box and compressive strength tests were carried out to examine the performance of SCC, and the results indicate that the Nan Su method could produce successfully SCC of high strength. Based on Nan Su mix design method, material quantities such as powder content ( Cement + Pozzolan ), fine aggregate, coarse aggregate, water and dosages of SP and VMA, required for 1 cu.m, are evaluated for High strength grade (M80) of Self Compacting Concrete (SCC) are estimated. Final quantities, of M80 grade SCC mix, is assumed after several trial mixes on material quantities computed using Nan Su mix design method subjected to satisfaction of EFNARC flow properties.

The utilization of fly ash in mix proportion of self-consolidation concrete

The application of Self-Consolidation concrete is needed for casting the concrete element with close-fitting reinforcement. This study was conducted to examine the effect of fly ash utilization on Self-Consolidation concrete properties and also to discover the optimum amount of fly ash as partially cement substitution in increasing mechanical properties of Self-Consolidation concrete. To coop with the problem three different mix design of Self-Consolidation concrete specimens were prepared to accomplish the laboratory experimental program. The mix proportion variation of fly ash replacement is 0%, 15% and 35% from cement weight. The specimens were prepared to test the properties of Self-Consolidation concrete, i.e.: slump flow test, flexural strength test, compressive strength test, and modulus of elasticity. Except slump flow test that was conducted for fresh concrete, the other tests were conducted after 28 days of curing time. After finishing testing programs, it is found that the utilization 15% of fly ash in production of Self-Consolidation concrete improve flexural strength of concrete whereas only a slightly decrease in compressive strength was found.

A mechanistic approach to predict built-in temperature in concrete pavements

The built-in temperature difference (BITD), defined as the temperature difference between the top and bottom of a slab at the final setting time, is an important parameter for analysing curling stress and slab deformation in concrete pavements. However, the available methods for estimating this parameter are very limited. A method to predict the BITD in a concrete pavement was therefore developed. To do this, a numerical model was developed to predict the temperature distribution in a concrete slab at early age using a transient one-dimensional finite-difference method. A mathematical equation for predicting concrete final setting time presented in the literature was used and incorporated in the numerical model to predict the BITD. The results of the numerical model showed good agreement with field data. Using the proposed model, the effects of climatic conditions, placement time, pavement thickness and concrete mix proportion on the BITD were also evaluated. The results showed that climatic conditions, placement time and concrete mix proportion have substantial effects on the BITD, whereas pavement thickness has only a slight effect. The proposed model can be used to predict the BITD in concrete slabs for given concrete mix design, placement time, pavement thickness and environmental conditions.

Evaluation of strength and durability of lean concrete mixes containing marble waste as fine aggregate

The extraction of marble and its processing as marble blocks is most common in several states of India. But the extensive growth of this industry has put adverse impact on the environment because of the production of huge amount of marble waste during extraction and processing. This experimental study highlights the impact of use of marble waste on the properties of lean concrete mix designed for the production of bricks. The basic objective of this experimental programme is to replace river sand in concrete by an optimum combination of quarry dust and marble waste in order to extract best performance in terms of strength and durability parameters. By varying the percentage replacement of fine aggregate with marble waste (0–100%), six concrete mix proportions were prepared for experimental purpose. The result shows that all these properties improved for complete substitution of fine aggregate with marble waste. It was found that compressive strength and flexural strength increased by 84% and 18.6%, respectively. The mixes were less reactive to the aggressive agents also. These advantages were derived due to the ability of marble fines impart necessary cohesiveness even at lesser water content which resulted in an impermeable microstructure.

Strength and durability of concrete containing recycled concrete aggregates

Recycled concrete aggregates (RCA) sourced from waste concrete are a sustainable alternative to natural crushed stone aggregates. The strength and durability properties of concrete containing RCA were evaluated by a comprehensive experimental investigation involving nine control mixes. The variables considered in the experimental study are water cement ratio, cement content in concrete and percentage replacement of coarse aggregate. The strength properties such as compressive strength, modulus of elasticity, splitting tensile strength and flexural strength are studied. Durability properties such as water absorption, sorptivity, acid attack resistance and chloride permeability are also determined. The test results showed that up to 25% of natural crushed stone aggregates in concrete may be replaced with RCA, without significantly affecting the strength of concrete and that the partial replacement of natural aggregates with RCA can be recommended in areas of moderate exposure conditions. Mathematical models developed in the study can be used for the a priori prediction of the strength parameters of RCA concrete. A mix design methodology using the developed models is proposed to aid practicing engineers to determine the mix proportions of RCA concrete.

Implications of uncompacted packing density of aggregates in self-compacting concrete mix proportioning

This study forms part of ongoing research on sandwich panels by the authors’ research team at CSIR-SERC, India, where there is a demand for self-compacting concrete with a limit on aggregate of size up to 10 mm, and with approximate cube strength and slump flow in the ranges 45–50 MPa and 600–700 mm, respectively. These requirements are achieved using a packing density concept for aggregates. In self-compacting concrete, when the concrete has not been compacted or vibrated during and after pouring, the uncompacted packing density of aggregates determines most of the aggregate-related attributes of the concrete. To obtain the uncompacted packing density of the aggregates, existing theoretical models for binary combination of aggregate are extended to ternary combination and the model with least deviation from the experimental procedure is chosen for the mix proportioning of aggregates in the self-compacting concrete. The extended Toufar model is identified as giving better uncompacted packing density in agreement with the experimental study, and is used for the proposed mix proportion. In the proposed mix proportioning method, slump flow is achieved without compromising the cube strength by optimising the aggregate volume, binder combination and superplasticiser dosage.

Metaheuristic-Based Machine Learning System for Prediction of Compressive Strength based on Concrete Mixture Properties and Early-Age Strength Test Results

Estimating the accurate concrete strength has become a critical issue in civil engi­neer­ing. The 28-day concrete cylinder test results depict the concrete's characteristic strength which was prepared and cast as part of the concrete work on the project. Waiting 28 days is important to guarantee the quality control of the procedure, even though it is a slow process. This research develops an advanced machine learning method to forecast the concrete compressive strength using the concrete mix proportion and early-age strength test results. Thirty-eight historical cases in total were used to create the intelligence prediction method. The results obtained indicate the effectiveness of the advanced hybrid machine learning strategy in forecasting the strength of the concrete with a comparatively high degree of accuracy calculated using 4 error indicators. As a result, the suggested study can provide a great advantage for construction project managers in decision-making procedures that depend on early strength results of the tests.

Factors Affecting the Bond Strength Between the Fly Ash-based Geopolymer Concrete and Steel Reinforcement

In this study, the effect of fly ash characteristics, the content of the fly ash and mix proportion of the Fly Ash-Based Geopolymer Concrete (FBGC) on the bond strength between the FBGC and steel reinforcement were examined. Australian fly ashes from five different sources (Eraring, Mt-Piper, Bayswater, Gladstone and Collie) were used in producing FBGC. A total of 45 FBGC mixes with different fly ash content (300, 400 and 500 kg/m3) and different proportions of alkaline activator were prepared. The use of different fly ashes and in different amounts showed significant differences in the bond strength between the FBGC and steel reinforcement. It was found that the fly ash characteristics including particle size distribution and the content of SiO2 Al2O3 and CaO influenced the bond strength of the FBGC significantly. The results showed that the FBGC that was mixed with Gladstone (GL) fly ash exhibited the highest average bond strength between the FBGC and steel reinforcement (25 MPa). While the FBGC that was mixed with Bayswater (BW) fly ash showed the lowest average bond strength between the FBGC and steel reinforcement (10 MPa). The results also indicated that the increase in the fly ash content in the FBGC significantly increased the bond strength between the FBGC and steel reinforcement. The bond strength of the FBGC responded differently to changes in the Na2SiO3/NaOH ratio in the alkaline activator corresponding to the use of different fly ash.

EFFECTS OF PALM OIL CLINKER AS COARSE AGGREGATES REPLACEMENT IN SELF CURING CONCRETE

Concrete, if properly design, can be one of the most durable material and widely used in construction due to its availability and good compressive strength. A good quality concrete can be produced not only through good design of concrete mix proportions but also good and proper curing process that ensure a complete hydration process of the cement. However, sometimes proper curing process was not provided during concreting on site due to various reasons. This study investigates the effects of 10 mm crushed Palm Oil Clinker (POC) as partial aggregates replacement to act as internal reservoirs in concrete to provide internal curing process of cement. This process or technique is also popularly known as self-curing process for concrete. The POC which has the density of 780 kg/m3 was used to replace 20% of the coarse aggregates. A water/cement ratio of 0.53 was used in the concrete mix design. Three different curing conditions were employed, namely, normal water curing, air curing and 7 days in water plus outside curing conditions. The workability of the POC and control concretes was determined through slump test. The concrete samples were tested for compression at the age of 3, 7 and 28 days while concrete prisms and cylindrical samples were tested at the age of 7 and 28 days. The experimental results show that the inclusion of POC was found to increase the workability of concrete by 27% but reduced the concrete compressive strength by about 6% compared with the control concrete. In addition, the flexural and tensile strengths of POC concrete were found to be less than the control concrete due to the properties of the POC which was lightweight and porous. The experimental results show that the porous structure of the POC aggregates can be utilised as water reservoir for the process of internal curing for the self-curing concrete.

Mechanical Properties of Self-Compacting Geopolymer Concrete Using Fly Ash and GGBS

Cement is the core content for the concrete mix. Manufacturing of cement causes CO2 emission which leads to the pollution, health and environmental problems like global warming to control over the adverse effect we can prefer geopolymer concrete which is not a cement concrete. Factory wastes such as fly ash, ground granulated blast furnace slag (GGBS), silica fume and Metakaolin can be used as alternate for cement. This study mainly focus on the ratio of fly ash and ground granulated blast furnace slag (GGBS) for optimum levels which nearly matches the cement concrete properties. This study involves the various tests like slump flow, compression testing, split tensile strength and flexural strength of self-compacting geopolymer concrete. Self-compacting concrete is a highly flowable concrete that spreads into the form without the need of mechanical vibration. Self-compacting concrete is a non-segregating concrete that is placed by means of its own weight. The advantages include improved constructability, Labour reduction, bond to steel, Flow into complex forms, reduced equipment wear etc. The aim of this study is to achieve an optimum self-compacting concrete geopolymer concrete mix proportion using fly ash and ground granulated blast furnace slag (GGBS). Then the study will be further extended by investigating the durability properties of self-compacting geopolymer concrete.

Effect of Alkaline Solution with Varying Mix Proportion on Geopolymer Mortar

Cement production is attributed by emission of carbon dioxide which causes severe environmental impacts. This has led to the invention of special construction materials which can replace cement. On the other hand, these construction materials (like Fly ash, Metakaolin) also need to be inexpensive and should possess all the characteristics of cementitious materials. In this project, the effect of geopolymerization on the properties of the end product were studied with varying distillation of NaOH solution (10M, 12M and 15M) for different mix proportion (1:1, 1:2 and 1:3). Curing was done for 1 day at a temperature of 60°C and 80°C respectively. The densities, compressive strength, alkalinity, co-efficient of absorption were determined. As a result, the experiments showed the effect of factors such as mix proportion, curing temperature and curing day on the physical and mechanical properties such as mix proportion of the geopolymer concrete. Results of NaOH concentration of 12M concentration cured for 24 hours at 80°C and 60°C showed better mechanical performance than the rest of the concentrations.

A quantitative method of approach in designing the mix proportions of fly ash and GGBS-based geopolymer concrete

This paper presents a systematic approach for selecting mix proportions for fly ash and GGBS-based geopolymer concrete. Very little information is available on complete methodology in designing the fly ash and GGBS-based geopolymer mix. The fly ash and GGBS were activated using sodium silicate and sodium hydroxide as alkaline activator solution. The Na2SiO3/NaOH (alkaline activator) ratio was taken as 2.5 and the concentration of NaOH solution was maintained at 8 M. The main parameters considered in this study were binder content and alkaline solution/binder ratio for various combinations of fly ash and GGBS. The variables considered in this experimentation include: binder content (360, 420 and 450 kg/m3), proportions of fly ash and GGBS (70–30, 60–40 and 50–50), alkaline solution/binder ratios (0.45, 0.50, 0.55 and 0.60) and curing condition (outdoor curing and oven curing). Results concluded that the GGBS content, alkaline solution/binder ratio and curing condition are found to be most influential parameters on compressive strength and workability of geopolymer concrete. The paper presents detailed examples of mix designs for various strengths.

Mechanical properties of kenaf fibrous pulverized fuel ash concrete

The main objective of the experimental work is to identify the mechanical properties of Kenaf Fiber incorporate with Ordinary Portland Cement (OPC) and Pulverised Fuel Ash (PFA) in the mix proportions of concrete. Kenaf Fibrous Concrete (KFC) and Kenaf Fibrous Pulverised Fuel Ash Concrete (KFPC) will be measured on physical and mechanical properties in order to investigate the suitability of this natural fiber as a composite material. A comparison of properties between these two composites will determine the density, workability, compressive, tensile, and flexural strength of the concrete. Eight different mixes with varying percentage of Kenaf fiber were prepared with 30N/mm2 strength at 28days ,56 days and 90 days. Short fiber with 25mm and 50mm length were randomly distribute in composite to enhance the tensile and durability. PFA was obtained by the process of burning in the Power Station Coal Ash at Tanjung Bin, Johor. The unburning powder from the process is called as a PFA generally suitable for cement replacement in the concrete mix. The pozzolanic reaction will improve the adhesion of cement gel, hence increased the properties of concrete in a long-term strength development. The result shows that the inclusion of Kenaf fiber improve tensile strength of composite, furthermore the 25% PFA mix increase the durability of concrete.