Admixture Replacement Research Articles

Agricultural waste as a replacement for admixture in concrete – A short review

There are a number of issues with managing the biomass waste generated from rice straw. These include field firing, which contributes to polluted air, and the organic decomposition procedures, which releases methane. There is a possibility that arises from the given situation where-in one can think of converting the waste to ash and then utilize the powder in the form of admixtures in concrete. It will help in reusing the waste materials found in abundance in a country like India with a phenomenal percent of the entire population feeding on rice. This culminates into realizing the amount of biomass waste produced by the country annually. In this era of ecological breakdown, one must review advanced methods which will help recycle the waste into forming green utilities. The aim of this review paper considers the properties of rice straw ash (RSA) and collectively studies the chemical influence of the same as a replacement of admixtures in variable percentages in concrete. The gamut of this paper revolves around reviewing the effect of RSA in place of admixtures in concrete. It is no mystery that production of cement which is an integral ingredient of concrete results in the emission of approximately 20% of global Carbon Dioxide (CO2). Globalization has led to faster growth and consumption of concrete structures that aid climate change. With utilization of waste materials as replacements in cement or admixtures, both environmental issues and waste disposal problems can be tackled at the same time.

Effect of different types of calcined crude kaolins and high purity metakaolin on corrosion resistance of reinforcement in concretes: Experimental evaluation and analytical modeling

In this experimental study, the corrosion characteristics of steel reinforcement bars embedded in concretes, which were produced by incorporation of metakaolin obtained from high purity metakaolin or calcined raw kaolins, were investigated. The linear polarization resistance (LPR) method was benefited as the corrosion monitoring method. In concrete production, 0.40 water/binder ratio, 350 kg/m3 total binder amount, two different mineral admixture replacement levels of 5% and 15% were used. In addition, control samples were produced to evaluate the effectiveness of mineral additives. Reinforced concrete samples manufactured for accelerated corrosion monitoring were submerged into NaCl solutions of two different concentrations (2% and 5% solutions) to provide rapid anodic reactions in corrosion process. Additionally, the electrical resistance values of the concretes were tested to assess the corrosion behavior. After the experimental results were achieved, the obtained data were evaluated statistically and a new mathematical estimation model was developed using the gene-expression programming (GEP) method taking into account the effective parameters. This model was also compared with the results of the multiple linear regression, which is a statistical method. The analysis of the results based on LPR technique showed that the modified samples yielded higher corrosion resistance than the plain samples in both solution exposure conditions. Among the mineral additives used, it was observed that those with metakaolin addition had the highest resistance. While the coefficient of determination (R2) of the testing set produced for the GEP prediction model was around 0.9, the value obtained by multiple linear regression was found to be 0.433.

Design Method for Concrete Mix Proportion Based on Indices of Strength and Durability of Concrete Exposed to Chloride Attack

In the current design code, concrete mix proportions are not based on durability parameters that can quantitatively design the requirement of service life for chloride-exposed structures. Multifactor calculation models of durability index are developed, and the replacement of mineral admixtures in concrete is determined according to predetermined concrete strength and durability requirements. The chloride diffusion coefficient and aging factor of concrete are chosen as index parameters for the resistance of concrete to chloride salts. A multifactor model of the chloride diffusion coefficient of concrete is then established by regression analysis based on the experimental data, and explicit expressions for the water-to-binder ratio and replacement of admixture were determined by solving the multivariate nonlinear equation system. By calculating the average compressive strength and chloride diffusion coefficient from their specified values, the mix proportion of concrete is determined. The superiority of the proposed method is demonstrated by the comparison with the current code. Lastly, an orthogonal experiment was conducted to demonstrate the validity of the proposed method for designing concrete mix proportions by referencing engineering practices. The results show that major parameters of concrete mix proportion can be determined quantitatively from structural design parameters such as compressive strength, chloride diffusion coefficient, and aging factor, satisfying the requirements of ultimate bearing capacity and service life for concrete structures in chloride environments, as demonstrated in this paper.

Early-age hydration characteristics and kinetics model of blended cement containing waste clay brick and slag

Low-carbon blended cement was prepared by mixing Portland cement, clay brick powder (CBP) and slag. The early-age hydration mechanism was studied by analyzing the hydration characteristics and kinetics parameters of blended cement with different admixture replacement rate, CBP to slag ratio and temperature. The results indicate that increasing admixture replacement rate accelerates cement hydration and leads to the displacement of exothermic peaks. However, the reduced C3S content in blended cement reduces the peak intensity and reaction rates of NG-I-D (nucleation and crystal growth - phase boundary reaction - diffusion) processes. Slag promotes the nucleation and growth of C–S–H gel slightly more than CBP before the third exothermic peak. Then, the slag reaction in the deceleration period consumes a lot of sulfate ions, resulting in the high third exothermic peak. High temperature provides nucleation driving force to accelerate the cement dissolution and ions migration, thus, the reaction rates of NG-I-D processes are increased as the temperature rises.

PROPERTIES OF CONCRETE CONTAINING CRUSHED LIMESTONE AS TOTAL REPLACEMENT OF NATURAL SAND AND RECYCLED ENGINE OIL

The rapid growth in the construction industry at the global level has made concrete the most widely used construction material throughout the world. Accordingly, the consumption of natural sand which is one the main raw material constituent of concrete is continuously growing. The demand for river sand is highly increasing due to its scarcity in the market. Manufactured sand produced by crushed rock is being considered as an appropriate alternative to replace river sand in concrete. In recent years, there is a growing interest in the use of crushed sand obtained from limestone quarries in some countries where river sand is not widely available”. The objective of this study is to investigate the effect of total replacement of the natural sand by fine aggregates obtained from crushed limestone. However, it needs more research on the crushed stone fine aggregates to reveal its engineering properties prior to utilization in concrete. Another objective of this study is to study the effect of using the waste engine oil as partial replacement of water reducing admixture. The use of waste engine oil in concrete is beneficial for the environment. It is to be noted that some countries are recycling this used oil but others are throwing it in the sea and harming the marine life. In this paper, different combinations and grading of fine lime stone and coarse aggregates were tried in order to attain the optimal proportion that provide an acceptable concrete performance in terms of workability and compressive strength. Also, different percentages of admixture replacement ranging from zero to one hundred percent of the used engine oil were tried in the selected optimal mixture proportion. The final selected proportion using engine oil and crushed limestone could be considered as an economical solution and friendly environmental concrete product.

A Sustainable Study on Permeable Concrete using Bagasse Ash and Rice Husk Ash as a Partial Replacement of Cement

Permeable concrete is a special concrete which consists of cement, coarse aggregate and water. Due to rapid growth of globalization and urbanization, the construction of concrete roads increasing day by day which leads to decrease in percolation of storm water, surface runoff occurring to the decrease in ground water table. In previous concrete, single sized aggregate is used to maintain the void ratio in the concrete. The cement paste is bonded with aggregate with a void ratio of 20%. In this investigation, concrete of M20 grade with water cement ratio of 0.38 is used. The properties of concrete were increased by using Rice husk ash and Bagasse ash in changed percentages (10%, 20%, 30%) by weight of cement and with the combination of rice husk ash and bagasse ash 10% (5%RA + 5%BA), 20%(10%RA+10%BA), 30%(15%RA+15%BA) are used. The compressive strength of cubes, split tensile of cylinders are casted, tested after 7 days and 28 days. After testing, the optimum percentages of replacement of admixtures are found in the Permeable concrete. Therefore the strength and durability properties of permeable concrete with the addition of bagasse ash and rice husk ash with partial replacement of cement are compared with conventional concrete.

THE MECHANICAL STRENGTH AND DRYING SHRINKAGE BEHAVIOR OF HIGH PERFORMANCE CONCRETE WITH BLENDED MINERAL ADMIXTURE

With the fast in population development, there are a higher demand in housing and infrastructure such as high-rise buildings and long-span bridges. Therefore, high performance concrete (HPC) is used massively due to its technical and economical advantages to fulfil people demands towards the concrete usage. Optimum mineral blended admixture replacement ratio with the addition of superplasticizer are the main component which contributed to the formation of HPC in terms of high workability, high strength and high durability. Hence, the optimal cement to blended mineral admixture ratio with the optimum addition of PCE type superplasticizer to achieve the targeted mechanical strength performance of G60 and reduce the drying shrinkage behavior which will results in crack of the ternary blended concrete is highlighted in this report. The influence of the addition of two mineral blended admixture, ground granulated blast furnace slag (GGBS) and pulverized fly ash (PFA) with the ordinary Portland cement (OPC) in different ratio on engineering performance and its drying shrinkage behavior in the age of 7 days, 28 days and 90 days based on different mineral blended admixture replacement level in 50%, 60%, 70% and 80% which GGBS to PFA ratio are controlled in 4:1 and the water to cement ratio was kept in 0.35 is studied. There are two types of PCE type superplasticizer (SP) was added to enhance the workability of the fresh concrete and act as slump retainer. Ternary blended concrete results in low early age (7 days) strength but the performance at later age (28 days and beyond) was encouraging. Results revealed that 80% replacement level have the remarkable result in terms of mechanical strength and drying shrinkage behavior. The study showed that, presence of mineral additives with superplasticizer will produce a similar or enhance the concrete strength properties with the inclusion of GGBS and PFA at the ratio of 4:1 up to 80% as cement replacement.

FLEXURAL BEHAVIOR OF SLURRY INFILTRATED FIBER CONCRETE (SIFCON) CONTAINING SUPPLEMENTARY CEMENTITIOUSE MATERIALS

Slurry Infiltrated fiber Concrete (SIFCON) is a relatively new high performance material and can be considered as a special type of Fiber Reinforced Concrete (FRC) with high fiber content. The matrix consists of flowing mortar or cement slurry which must infiltrate properly through the fiber network placed in molds. SIFCON possessing excellent mechanical properties coupled with large ductility and toughness values. SIFCON has found application in area where high ductility and energy absorption are needed especially in seismic-resistant reinforced concrete frames and in structure under abnormal or explosive loads. Other successful applications include pavement overlays, repair of prestressed beams and repair of structural reinforced concrete element.The main aim of this study is to determine the effect of hooked ended steel fiber content and mineral admixture replacement silica fume (SF) on strength and deformation characteristics of SIFCON specimens under flexural loading. Three volume fraction of steel fiber (6, 8.5, and 11) % were used in this investigation .The percentage of SF replacement was (10%), by weight of cement in SIFCON slurry. Both the flexural strength and toughness characteristic were carried out by testing specimens of 100*100*400 mm at the age of 7and 28 days. The results obtained from these tests were compared with those carried out on conventional fiber reinforced mortar (FRM) with 2% fiber content, as control specimens. The test results show superior characteristics of SIFCON ,as compared with normal FRM ,which were affected in positive manner by using cementitiouse materials (SF) as a partial replacement by weight of cement, and with increasing the volume fraction of steel fiber. The flexural strength and toughness value up to (28.08 MPa ) and (159 N.mm),respectively were obtained at age of 28 days.

A Computer‐Aided Approach to Pozzolanic Concrete Mix Design

Pozzolanic concrete has superior properties, such as high strength and workability. The precise proportioning and modeling of the concrete mixture are important when considering its applications. There have been many efforts to develop computer‐aided approaches for pozzolanic concrete mix design, such as artificial neural network‐ (ANN‐) based approaches, but these approaches have proven to be somewhat difficult in practical engineering applications. This study develops a two‐step computer‐aided approach for pozzolanic concrete mix design. The first step is establishing a dataset of pozzolanic concrete mixture proportioning which conforms to American Concrete Institute code, consisting of experimental data collected from the literature as well as numerical data generated by computer program. In this step, ANNs are employed to establish the prediction models of compressive strength and the slump of the concrete. Sensitivity analysis of the ANN is used to evaluate the effect of inputs on the output of the ANN. The two ANN models are tested using data of experimental specimens made in laboratory for twelve different mixtures. The second step is classifying the dataset of pozzolanic concrete mixture proportioning. A classification method is utilized to categorize the dataset into 360 classes based on compressive strength, pozzolanic admixture replacement rate, and material cost. Thus, one can easily obtain mix solutions based on these factors. The results show that the proposed computer‐aided approach is convenient for pozzolanic concrete mix design and practical for engineering applications.

Effects of Shrinkage‐Compensation on Mechanical Properties and Repair Performance of Strain‐Hardening Cement Composite Materials

This paper describes the effects of expansive admixture on the mechanical properties of strain‐hardening cement‐based composite (SHCC) mixtures. Also, this study investigates structural performance of reinforced concrete (RC) beam specimens repaired with SHCC and Ex‐SHCC (SHCC with expansive admixture). In this study, SHCC and Ex‐SHCC mixtures with two specified compressive strength values of 30 MPa and 60 MPa and the fiber volume fraction of 1.5% were investigated. The expansive admixture replacement ratio of 10% by cement weight was used in this study. The test results indicate that the compressive, tensile, and flexural strength values of the SHCC mixtures increased when expansive admixture was included in the mix; however, their toughness and ductility decreased. The study results also show that the application of both SHCC and Ex‐SHCC mixtures to repair damaged RC beam specimens can lead to significant structural performance improvement by mitigating crack damage and increasing ductility.

Effect of calcium leaching on the pore structure, strength, and chloride penetration resistance in concrete specimens

In radioactive waste repositories constructed underground and on shorelines, concrete members can remain in contact with groundwater for a long period. However, even pure water creates concentration gradients which lead to the diffusion of Ca ions from the pore water and the degradation of the underground concrete. Therefore, the purposes of this study are to investigate not only the alteration of the pore structure and the loss of compressive strength associated with dissolution but also the characteristics of chloride penetration after leaching-related degradation.The results show that as the leaching period increases, the volume of pores with diameters ranging from 50nm to 500nm is greatly increased. Also, pores larger than 200nm in size rapidly increase in number during the initial leaching time, while those smaller than 200nm increase in number only gradually. Furthermore, the residual strength of the leached part with OPC ranges from 35% to 60%. In addition, those of the mineral admixture replacement ranged from 23% to 50%. The chloride diffusion coefficient measured by the chloride profile increased two-to-five-times with the leaching duration.

RELATION BETWEEN PHASE COMPOSITION AND COMPRESSIVE STRENGTH OF VARIOUS HARDENED CEMENT PASTE

本研究では、各種セメント硬化体の相組成が圧縮強度に及ぼす影響について検討を行った。検討を行う際には、水和物の物理的性質から決定される空隙率やゲル空隙比を算出し、それらと圧縮強度の関係を評価した。硬化体の相組成を評価した結果、混和材の置換により長期材齢の空隙量が減少した。これは長期的に水和物の生成量が増加すること、またC-S-Hの密度が低下し水和物体積が増加するためである。また圧縮強度は、空隙率やゲル空隙比と概ね同一線上で評価することが可能であることを確認した。より高精度な評価を行うためには、空隙構造の変化も考慮に入れた検討が必要と示唆された。

Improvement on SIFCON Performance by Fiber Orientation and High-Volume Mineral Admixtures

The effects of steel fiber alignment and high-volume mineral admixture replacement [Class C fly ash (FA) and ground granulated blast furnace slag (GGBS)] on the mechanical properties of SIFCON (Slurry Infiltrated Fiber Concrete) have been investigated. Ordinary portland cement was replaced with 50% (by weight) FA or GGBS in SIFCON slurries, and two different steel fiber alignments (random and oriented in one direction) were used. Test results showed that FA and GGBS replacement positively affected mechanical properties (compressive and flexural strength and fracture energy) and fiber alignment is an important factor for superior performance. Binary combination of improved matrices (low water/binder ratio and mineral admixture replacement) and proper fiber orientation enhances mechanical performance, particularly flexural properties of SIFCON. Flexural strength and fracture energy of this composite are 138 MPa and 195,815 N/m, respectively. Scanning electron microscope investigations revealed tobermorite-like structures having different morphology such as foiled, fibrous, and honeycomb with low Ca/Si ratio after autoclaving. Mercury porosimeter tests showed the decreasing of total porosity and pore refinement with FA or GGBS.

Leaching tests on different mortars using accelerated electrochemical method

In designing radioactive waste repositories, it is necessary to predetermine the degree of concrete performance change due to leaching degradation. Leaching tests were carried out on different mortars using an electrochemical method. With this method, a potential gradient is applied across the specimen, which accelerates the dissolution of cement hydrate from mortar in contact with water. Tests were carried out using various sand/cement ratios, water/cement ratios, and pozzolanic admixture [blast-furnace slag (BF) and silica fume (SF)] replacement for a part of the cement to determine differences in the quality and quantity of cement hydrate. The amount of Ca 2+ ions entering the water varied depending on the mix proportions. It decreased with sand content, but increased with water/cement ratio, and it varied with the kind of pozzolanic admixture and the replacement ratio. The pore volume of the degraded specimens increased as a result of cement hydrate dissolution. The water permeability of the mortar specimens increased by about one to two orders of magnitude due to leaching degradation. The compressive strength of the degraded mortar specimens decreased by 20% to 60%. There was good correspondence between each performance change and pore volume change due to leaching degradation. Pozzolanic admixture replacement for a part of the cement was very useful in achieving a durable concrete that resists leaching and shows a small loss of performance after leaching.