Mechanical Properties of HPC Incorporating Fly Ash and Ground Granulated Blast Furnace Slag After Exposure to High Temperatures

The behavior of concrete structures after being exposed to elevated temperatures is considered one of the great vital concerns in Civil Engineering. Moreover, as elevated temperature have adverse effects on the mechanical properties of concrete members, it’s important to find solutions to improve these properties at elevated temperature. This study aims to investigate the effect of supplementary cementitious materials (SCM) on the high performance concrete (HPC) compressive, tensile, and flexural strengths after exposure to different temperatures of 200 °C, 400 °C, 600 °C, and 800 °C. In preparing HPC, different parameters were considered including SCM type, fly ash (FA) or ground granulated blast furnace slag (GGBFS), adding 0.5% (by volume fraction) steel fiber (SF), polypropylene fiber (PP) and hybrid fibers. The results were compared with those for high strength concrete (HSC) and normal strength concrete (NSC). The results showed that using FA and GGBFS, SF, and hybrid fibers can significantly improve the residual mechanical properties of HPC, while using PP fiber has an adverse effect on the residual mechanical properties of HPC especially residual tensile and flexural strengths. The standard code curves underestimate the residual mechanical properties of HPC after 200 °C

Properties of Cement Composites Utilizing of Bentonite: A Review

The use of bentonite clay slurries in civil and geotechnical engineering dates back to Veder\u27s pioneering work in 1953. Since then, bentonite has been used for various applications such as the construction of bored piles and diaphragm walls. Plastic concrete walls also require sufficient strength and modulus to adapt to the surrounding environment, and the characteristics and different forms of bentonite commercially available were reviewed in this paper.This paper reviews the properties and applications of bentonite, including its use in cement-bentonite composites for remedial cut-off wall construction. Cement-bentonite grouts offer advantages over bentonite grouts in terms of ease of use and adjustability of strength.Cement-bentonite composites were found to be promising materials for remedial cut-off wall construction due to their ability to meet requirements for strength, stiffness, and permeability. By regulating the mix proportions, the strength of the set grout can be adjusted to match that of the surrounding ground. Cement-bentonite grouts also offer advantages over traditional bentonite grouts, as they are easier to use, offer a longer working period before setting, and can be forgiving if the user deviates from the design formula or the mixing technique. This paper provides useful information for those working with bentonite and cement-bentonite composites in civil and geotechnical engineering applications

Properties of Cement Composites Utilizing of Bentonite: A Review

The use of bentonite clay slurries in civil and geotechnical engineering dates back to Veder\u27s pioneering work in 1953. Since then, bentonite has been used for various applications such as the construction of bored piles and diaphragm walls. Plastic concrete walls also require sufficient strength and modulus to adapt to the surrounding environment, and the characteristics and different forms of bentonite commercially available were reviewed in this paper.This paper reviews the properties and applications of bentonite, including its use in cement-bentonite composites for remedial cut-off wall construction. Cement-bentonite grouts offer advantages over bentonite grouts in terms of ease of use and adjustability of strength.Cement-bentonite composites were found to be promising materials for remedial cut-off wall construction due to their ability to meet requirements for strength, stiffness, and permeability. By regulating the mix proportions, the strength of the set grout can be adjusted to match that of the surrounding ground. Cement-bentonite grouts also offer advantages over traditional bentonite grouts, as they are easier to use, offer a longer working period before setting, and can be forgiving if the user deviates from the design formula or the mixing technique. This paper provides useful information for those working with bentonite and cement-bentonite composites in civil and geotechnical engineering applications

Compressive strength prediction of Portland cement concrete with age using a new model

Based on the existing experimental data for compressive strength values of different concrete mixes, a statistical analysis for the gathered data was conducted. The analysis revealed a model for predicting the compressive strength of concrete mixes at any age with the help of two constants (A) and (B) that are considered as a characteristic property for a concrete mix. The constant (A) is introduced as a rate of strength gain constant whereas, (B) is introduced as grade of strength constant. Once the values of constants (A) and (B) are defined for a concrete mix, the compressive strength at any age could be simply predicted without collecting data at that age. The values of (A) and (B) could be determined by one of two methods. Solving two simultaneous equations at two different ages while performing either design or trial concrete mix is a method that could be used to define the two constants. Other method is based on concrete strength at 28-day age. The proposed model was studied for different concrete mixes. The study covered some parameters including the influence of, mineral admixtures as a partial replacement of cement, metakaolin, nano silica fume, curing in water or lime and the effect of curing temperature. The analysis reveals that mixes containing no admixtures, mixes containing silica fume and cured at normal temperature, mixes containing nano silica and cured in water are following with high accuracy the proposed model

Evaluation of consistency properties of freshly mixed concrete by cone penetration test

This study is directed to evaluate the ability of using cone penetration test as a simple method to investigate the consistency level of fresh concrete. A cone of 30° apex angle attached with different load values was used. Eighteen concrete mixes divided into three groups were conducted. Three types of coarse aggregate were tried. Crushed dolomite, round gravel, and crushed basalt all of 20 mm maximum grain size were investigated. For each type of coarse aggregate, six levels of concrete consistency calibrated by standard slump test were tried. For the investigated mixes and at a specified consistency level, the displaced volume values were directly proportional to the applied load. The inclination of this relation is termed as the displaced volume rate (D.V). The results of cone penetration were analyzed and compared to the corresponding slump test values. The displaced volume per unit mass, bearing strength, as well as shear yield strength were the evaluated properties. The results introduce the cone penetration test as a simple instrument that could be adopted either at a laboratory or at site to evaluate fresh concrete workability. Moreover, it is being more sensitive compared to the well known slump test. It can simply and clearly distinguish between stiff mixes as well as floppy ones. Very useful numerical limits for the evaluated properties controlling the workability levels of very low, low, medium, high and very high were proposed

Flow properties of fresh concrete by using modified geotechnical Vane shear test

An experimental investigation has been performed to study the efficiency of using modified geotechnical Vane shear test to evaluate the fresh properties of concrete. Different concrete mixes with different coarse aggregates (both type and size) were conducted. Moreover different shapes and sizes of Vane probes were investigated. Also the influence of using enhancing workability admixtures was studied. The results of the shear Vane test were statistically analyzed and compared with those for standard tests. The results reveal that the Vane shear test with modified blades can be simply executed to measure workability of concrete anywhere with a good efficiency. Useful equations with good correlation coefficients are established between the well known standard tests include compacting factor, slump, VeBe and flow tests and the Vane yield method. Size effect phenomenon related to Vane size is recorded for the Vane yield stress results. The results of the Vane yield stress could clearly distinguish between not only mixes made up of different aggregate types but also the aggregate maximum nominal size. The results of the Vane shear test are clearly affected by using enhancing workability admixtures and its dosage. A direct proportion between Vane yield stress results and the companion compacting factors test values is strongly noticed which introduces the Vane test method as a simple instrument that could be simply adapted anywhere to measure the workability of fresh concrete instead of compacting factor that is a laboratory apparatus

Performance of Portland cement mixes containing silica fume and mixed with lime-water

This study is planned to investigate the properties of Portland cement mixtures containing silica fume and mixed with saturated lime water. The conducted Portland cement mixes included three groups; cement pastes, cement mortars and cement concrete mixes. The main parameters were; type of mixing solution (water or lime-water) as well as the percentage of Portland cement replaced by silica fume. Consistency level, times of initial and final settings, compressive strength development, existence and intensity of CH crystals with age, pozzolanic activity as well as efficiency of the investigated matrices to delay the corrosion of embedded steel bars were the investigated properties. Test results show that using lime-water in mixing enhances consistency degree compared to the corresponding control mixes. Furthermore, it delays both initial and final setting times compared with traditional water due to the common ion effect principles. Moreover, combined use of lime-water and silica fume enhances the pozzolanic reaction that was identified by the strength development at both early and later ages. The existence of CH crystals for higher percentages of silica fume (up to 30%) for further reaction at later ages was observed by XRD results. Moreover, combined use of silica fume and lime-water ensures a high alkaline media around steel bars from the moment of ingredients mixing as long as later ages despite of pozzolanic reaction that was identified from results of chloride attack

Fracture properties of self-compacting fiber-reinforced concrete

Self-compacting concrete (SCC) is an innovative concrete that does not necessitate vibration for placing and compaction. Nineteen concrete mixes were investigated including a control mix without fibers as well as eighteen SCC with fibers (SCFRC) mixes. Three types of fibers (polypropylene, glass and steel) were used. Slump flow, L-box, V-funnel as well as column segregation tests were conducted to assess the fresh properties. Whereas, compressive, splitting tensile and flexural strengths were measured to assess the hardened properties of SCFRC. Three point bending tests were performed for the purpose of assessing the fracture properties of SCFRC. Test results showed that the inclusion of fibers to produce SCFRC mixtures remarkably enhanced the fracture properties including fracture energy (Gf) and fracture toughness (K1c). Inclusion of steel fibers with 2% volume fractions showed an improvement with 26.9 times for Gf over the control mix. Whereas, 104% increase in K1c was recorded for the same mix over the mix without fibers. Adding fibers to SCC to produce self-compacting fiber reinforced concrete (SCFRC) will expand its advantages. However, the application fields still need to understand the properties of SCFRC

Predicting the ingredients of self compacting concrete using artificial neural network

Self compacting concrete (SCC) is a highly flowable type of concrete that spreads into form without the need of mechanical vibration. This paper presents a comparative study between two methodologies which have been applied on two different data sets of SCC mixtures, which were gathered from the literature, using artificial neural network (ANN). The two methodologies aim to get the best prediction accuracy for the SCC ingredients using the 28-day compressive strength and slump flow diameters as inputs of the ANN. In the first methodology, the ANN model is constructed as a multi input â multi output neural network with the six ingredients as outputs. In the second methodology, the ANN model is constructed as a multi input â single output neural network where the six ingredient outputs are predicted separately from six different neural networks of multi input â single output type. Also, the influence of the mixes homogeneity on the prediction accuracy is investigated through the second data set. The results demonstrate the superiority of the second methodology in terms of accuracy of the predicted outputs. Moreover, the uniformity of the training data assures the accuracy of the predicted ingredients. Keywords: Self compacting concrete (SCC), Artificial neural network (ANN), Concrete mix design, Concrete compressive strength, Slump flo

Properties of Portland cement concrete cast with magnetized water: a review

The water utilized in concrete manufacture plays an important role within the concrete mix, beginning from controlling the process of hydration of cement, besides appropriate curing to achieve the required strength, not to mention controlling the workability and durability of the concrete structure. The utmost significant challenge for concrete technology is to improve the properties of concrete. Nowadays, the engineering field needs to produce structures in harmony with the concept of sustainable development through the utilization of high-performance materials with an eco-friendly impact that is produced at a low-cost. The magnetic water (MW) provides one of the utmost towards this objective. The cost of magnetizing water is low because of the simple instruments used and the cost can be adapted to the scale of the work. In the last two decades, a new technology, so-called MW technology, has been extended to use in concrete manufacturing. Therefore, currently, the researchers are interested in the use of MW in the manufacture of cementitious materials helping to rationalize the cement usage and reducing reliance on chemical additives that have a negative environmental impact. Consequently, this paper presents the effect of the magnetization process in the structure of water molecules, the main properties of water. Additionally, the effect of using MW on the fresh and mechanical properties, as well as the durability characteristics and performance of cementitious materials have been reviewed. Moreover, the factors that affect the magnetization process of water, which highlighted discuss in this study. The results revealed that using MW significantly enhances the flowability and the characteristic strengths of cementitious materials as well as the durability properties