•Utilization and the efficiency of GGBFS on the properties of mortar/concrete was discussed and reviewed.•Production process and reaction mechanism of GGBFS were presented.•Fresh, hardened, ...permeability and durability properties of GGBFS included mortar/concrete were discussed.
Ground granulated blast furnace slag (GGBFS) is a byproduct from the blast-furnaces of iron and it is a very beneficial in the mortar and concrete production. The present paper reviews the literature related to the utilization and the efficiency of GGBFS on the properties of mortar/concrete. Firstly, general information about GGBFS production, reaction mechanism and heat of hydration are presented. Then, workability, setting time, bleeding, rheological properties, slump loss, segregation resistance and early age cracking potential and finishability are addressed among the fresh concrete properties. Strength and rate of strength gain, modulus of elasticity, creep, shrinkage, influence of curing on performance of GGBFS, permeability, resistance to freeze/thaw cycles, carbonation resistance, deicing salt scaling, alkali–silica reaction and sulfate attack are among reviewed hardened concrete properties.
•Microstructural and mechanical properties of the AAS mortars were investigated.•Variation in mechanical and microstructural properties depend on elevated temperature and curing type were ...investigated.•Applied curing regime and exposed temperature level had a significant effect on the TGA, XRD and SEM images of AAS mortars.
This article reports a study on the microstructural and mechanical properties of the Alkali Activated Slag mortars (AAS) upon exposing to the elevated temperatures up to 800°C. Slag cement is activated by sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions with silicate modulus (Ms=SiO2/Na2O) of 1.0 and sodium (Na) dosages of 5%. AAS mortars were being subjected to the ambient and high temperature curing (6h under 60°C) after undisturbed for 24h in mold at room temperature. Ordinary Portland cement (OPC) mortar was also prepared as control. Bending and compression tests were conducted at ambient temperature and after exposure to high temperatures at 28days. Both AAS and OPC mortars were subjected to the X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) tests to find out the microstructural variation due to the exposed temperature level. Test results revealed that the high temperature resistance of the alkali activated slag mortars and Portland cement mortars are clearly different from each other’s. Contrary to the expectations, brilliant mechanical and high temperature resistance might not be observed at the alkali activated slag mortars irrespective of the applied cured conditions. Additionally, applied curing regime and exposed temperature level had a significant effect on the TGA, XRD and SEM images.
Drying shrinkage can be a major reason for the deterioration of concrete structures. The contraction of the material is normally hindered by either internal or external restraints so that tensile ...stresses are induced. These stresses may exceed the tensile strength and cause concrete to crack. The present study investigated compressive strength and particularly drying shrinkage properties of self-compacting concretes containing binary, ternary, and quaternary blends of Portland cement, fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume (SF), and metakaolin (MK). For this purpose, a total of 65 self-compacting concrete (SCC) mixtures were prepared at two different water to binder ratios. It was observed that drying shrinkage lessened with the use of FA, GGBFS, and MK while incorporation of SF increased the drying shrinkage.
One of the most damaging environmental conditions to concrete structure is cyclic freezing and thawing. This paper discusses the influence of the high volumes of fly ash (FA) and micro ...poly-vinyl-alcohol (PVA) fibers on the cyclic freeze–thaw resistance and microstructure of the Engineered Cementitious Composites (ECC). ECC mixtures with two different FA–cement (FA/C) ratios (1.2 and 2.2 by weight), and at constant water-cementitious materials (fly ash and cement) ratio of 0.27 are prepared. To compare the behavior of ECC with ECC matrix, all of the preceding properties are also investigated for ECC matrix mixtures of same composition without PVA fiber. For frost resistance, mixtures are exposed to the freeze and thaw cycles up to 300
cycles in accordance with ASTM C666, Procedure A. Experimental tests consist of measuring the residual mechanical properties (flexural strength, mid-span beam deflection and flexural stress – deflection curve), ultrasonic pulse velocity and mass loss. The roles of PVA fibers and FA are discussed through the analysis of microstructure and fiber–matrix interactions as function of frost exposure. The microstructural characterization by measuring pore size distributions is examined before and after exposure to frost deterioration by using mercury intrusion porosimetry (MIP). The air-void characteristics of mixtures are also studied using linear transverse method. Test results confirm that both ECC mixtures with high volumes of FA remain durable, and show a tensile strain capacity of more than 2% even after 300 freezing and thawing cycles. On the other hand, before completing 300 freezing and thawing cycles, matrix (ECC without fiber) specimens have severely deteriorated, requiring removal from the freeze–thaw machine. Therefore, results indicate that the addition of micro PVA fiber to the ECC matrix substantially improved the frost resistance. The results of freeze–thaw tests also indicated that the reduction of residual physical and mechanical properties with increasing number of freeze–thaw cycles is relatively more for ECC mixture with FA/C ratio of 2.2 than for ECC mixture with FA/C ratio of 1.2.
Self-compacting concretes (SCCs) have brought a promising insight into the concrete industry to provide environmental impact and cost reduction. However, the use of ternary and especially quaternary ...cementitious blends of mineral admixtures have not found sufficient applications in the production of SCCs. For this purpose, an experimental study was conducted to investigate properties of SCCs with mineral admixtures. Moreover, durability based multi-objective optimization of the mixtures were performed to achieve an optimal concrete mixture proportioning. A total of 22 concrete mixtures were designed having a constant water/binder ratio of 0.44 and a total binder content of 450
kg/m
3. The control mixture included only a Portland cement (PC) as the binder while the remaining mixtures incorporated binary, ternary, and quaternary cementitious blends of PC, fly ash (FA), ground granulated blast furnace slag (S), and silica fume (SF). Fresh properties of the SCCs were tested for slump flow diameter, slump flow time, L-box height ratio, and V-funnel flow time. Furthermore, the hardened properties of the concretes were tested for sorptivity, water permeability, chloride permeability, electrical resistivity, drying shrinkage, compressive strength, and ultrasonic pulse velocity. The results indicated that when the durability properties of the concretes were taken into account, the ternary use of S and SF provided the best performance.
This paper discusses the influence of high volumes of fly ash and micro polyvinyl alcohol (PVA) fibers on the fire resistance and microstructure of engineered cementitious composites (ECC). ...Composites containing two different contents of fly ash as a replacement for cement (55 and 70% by weight of total cementitious materials) are examined. To determine the effects of microfibers and ultrahigh ductility of ECC, ECC matrix mixtures of similar composition except PVA fiber are also produced and tested for the fire resistance. The mixtures are exposed to temperatures up to 800°C for one hour. Fire resistances of the mixtures are then quantified in terms of the residual mechanical properties (strength, stress-strain curve, deflection, and stiffness) and mass loss. The role of PVA fibers and fly ash is discussed through the analysis of microstructure and fiber-matrix interactions as a function of heat treatment. The microstructural characterization is examined before and after exposure to fire deterioration by using scanning electron microscopy and the pore size distribution is obtained by mercury intrusion porosimetry. Results indicate that adding micro PVA fiber to the ECC matrix substantially improves the fire resistance and eliminates the explosive spalling behaviors of the ECC matrix. Fire resistance of ECC mixtures is further improved with the increase of fly ash content.
This study investigated the dual effect of freeze–thaw cycles with sodium sulfate solution on the performance of non-air-entrained Engineering Cementitious Composites (ECCs) with high volumes of ...slag. ECC specimens containing three different levels of slag content as a replacement for cement (55%, 69% and 81% by weight of total cementitious material) were exposed to aggressive sodium sulfate solution under freezing–thawing cycles. The load–deflection response associated with ultimate mid-span deflection and flexural strength/stiffness was determined, along with crack development behavior. For comparison purposes, the freezing–thawing resistance (in water) of control ECC specimens was also evaluated. Modified point count method air-void parameters, compressive strength, porosity, water absorption and sorptivity tests were also conducted on the virgin ECC specimens (those not exposed to freezing–thawing cycles in water or aggressive sodium sulfate solution). The test results for the virgin specimens revealed that increased slag content (S/PC) improved the ductility, hardened air content, water absorption, porosity and sorptivity of ECC, while marginally decreasing the compressive and flexural strengths. Freeze–thaw cycles in water or sodium sulfate solution showed that the ductility of ECC specimens decreased remarkably, irrespective of slag content and applied freezing–thawing process. Reduction in mass loss was at minimal levels and no significant behavior change was monitored between the specimens undergoing freeze–thaw cycling in water and the aggressive sodium sulfate solution. Moreover, the decrease in flexural stiffness was more evident than the reduction of the flexural strength for all ECC mixtures.
High Strength Concrete (HSC) is defined as concrete that meets special combination of performance and uniformity requirements that cannot be achieved routinely using conventional constituents and ...normal mixing, placing, and curing procedures. HSC is a highly complex material, which makes modelling its behavior very difficult task. This paper aimed to show possible applicability of neural networks (NN) to predict the compressive strength and slump of HSC. A NN model is constructed, trained and tested using the available test data of 187 different concrete mix-designs of HSC gathered from the literature. The data used in NN model are arranged in a format of seven input parameters that cover the water to binder ratio, water content, fine aggregate ratio, fly ash content, air entraining agent, superplasticizer and silica fume replacement. The NN model, which performs in Matlab, predicts the compressive strength and slump values of HSC. The mean absolute percentage error was found to be less then 1,956,208% for compressive strength and 5,782,223% for slump values and
R
2 values to be about 99.93% for compressive strength and 99.34% for slump values for the test set. The results showed that NNs have strong potential as a feasible tool for predicting compressive strength and slump values.
The optimization of composite materials such as concrete deals with the problem of selecting the values of several variables which determine composition, compressive stress, workability and cost etc. ...This study presents multi-objective optimization (MOO) of high-strength concretes (HSCs). One of the main problems in the optimization of HSCs is to obtain mathematical equations that represents concrete characteristic in terms of its constitutions. In order to solve this problem, a two step approach is used in this study. In the first step, the prediction of HSCs parameters is performed by using regression analysis, neural networks and Gen Expression Programming (GEP). The output of the first step is the equations that can be used to predict HSCs properties (i.e. compressive stress, cost and workability). In order to derive these equations the data set which contains many different mix proportions of HSCs is gathered from the literature. In the second step, a MOO model is developed by making use of the equations developed in the first step. The resulting MOO model is solved by using a Genetic Algorithm (GA). GA employs weighted and hierarchical method in order to handle multiple objectives. The performances of the prediction and optimization methods are also compared in the paper.
The paper presented herein investigates the effects of using supplementary cementitious materials in binary, ternary, and quaternary blends on the fresh and hardened properties of self-compacting ...concretes (SCCs). A total of 22 concrete mixtures were designed having a constant water/binder ratio of 0.32 and total binder content of 550 kg/m^sup 3^. The control mixture contained only portland cement (PC) as the binder while the remaining mixtures incorporated binary, ternary, and quaternary cementitious blends of PC, fly ash (FA), ground granulated blast furnace slag (GGBFS), and silica fume (SF). After mixing, the fresh properties of the concretes were tested for slump flow time, L-box height ratio, V-funnel flow time, setting time, and viscosity. Moreover, compressive strength, ultrasonic pulse velocity, and electrical resistivity of the hardened concretes were measured. Test results have revealed that incorporating the mineral admixtures improved the fresh properties and rheology of the concrete mixtures. The compressive strength and electrical resistivity of the concretes with SF and GGBFS were much higher than those of the control concrete.PUBLICATION ABSTRACT
