The development of new binders, as an alternative to traditional cement, by the alkaline activation of industrial by-products (i.e. ground granulated slag and fly ash) is an ongoing research topic in ...the scientific community Puertas F, Amat T, Jimenez AF, Vazquez T. Mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres. Cem Concr Res 2003;33(12): 2031–6. The aim of this study was to investigate the feasibility of using and alkaline activated ground Turkish slag to produce a mortar without Portland cement (PC).
Following the characterization of the slag, mortar specimens made with alkali-activated slag were prepared. Three different activators were used: liquid sodium silicate (LSS), sodium hydroxide (SH) and sodium carbonate (SC) at different sodium concentrations. Compressive and flexural tensile strength of alkali-activated slag mortar was measured at 7-days, 28-days and 3-months. Drying shrinkage of the mortar was measured up to 6-months. Setting times of the alkali-activated slag paste and PC paste were also measured.
Setting times of LSS and SH activated slag pastes were found to be much slower than the setting time of PC paste. However, slag paste activated with SC showed similar setting properties to PC paste.
LSS, SH and SC activated slag mortar developed 81,
29, and 36
MPa maximum compressive strengths, and 6.8,
3.8, and 5.3
MPa maximum flexural tensile strengths at 28-days. PC mortar developed 33
MPa compressive strength and 5.2
MPa flexural tensile strength. LSS and SH activated slag mortars were found to be more brittle than SC activated slag and PC mortars.
Slag mortar made with LSS had a high drying shrinkage, up to six times that of PC mortar. Similarly, slag mortar made with SH had a shrinkage up to three times that of PC mortar. However, SC activated slag mortar had a lower or comparable shrinkage to PC mortar. Therefore, the use of SC as an activator for slag mortar is recommended, since it results in adequate strength, similar setting times to PC mortar and comparable or lower shrinkage.
•Transport properties of HVFA or slag concretes were studied after high temperature.•Transport properties of concrete increased significantly after exposure to 400°C.•Slag concrete behaved better ...than fly ash concrete for all high temperature.•30–50% fly ash or 50–70% slag replacement are optimal content for high temperature.
In this study, transport properties of high volume fly ash or slag incorporated concretes after exposure to high temperature were investigated experimentally. Concretes with the content of 0%, 30%, 50%, 70% and 90% fly ash or slag were prepared and moist cured until 28days. Fly ash and slag concrete samples were exposed to high temperatures at 400°C, 600°C and 800°C for an hour in a computer controlled, electrically heated kiln. Then, the specimens were left to cool down to the laboratory temperature. Subsequently, absorption, void ratio, sorptivity, chloride ion permeability and compressive strength tests were carried out on the specimens. Test results showed that transport properties of concrete increased significantly after exposure to 400°C, as well as, compressive strength dropped remarkably. Test results also revealed that inclusions of fly ash or slag influenced the transport properties considerably. It is concluded that a blend of, at about, 30–50% fly ash and 50–70% slag as a cement replacement is found to be the optimal content for exposure to high temperature. Rapid chloride permeability test results revealed that slag concrete bound more chloride than fly ash concrete. Slag concrete behaved better than fly ash concrete did under high temperature exposure for all case, some of slag concrete even behaved better than Portland cement concrete in terms of compressive strength reduction.
In this study, an artificial neural networks study was carried out to predict the compressive strength of ground granulated blast furnace slag concrete. A data set of a laboratory work, in which a ...total of 45 concretes were produced, was utilized in the ANNs study. The concrete mixture parameters were three different water–cement ratios (0.3, 0.4, and 0.5), three different cement dosages (350, 400, and 450
kg/m
3) and four partial slag replacement ratios (20%, 40%, 60%, and 80%). Compressive strengths of moist cured specimens (22
±
2
°C) were measured at 3, 7, 28, 90, and 360 days. ANN model is constructed, trained and tested using these data. The data used in the ANN model are arranged in a format of six input parameters that cover the cement, ground granulated blast furnace slag, water, hyperplasticizer, aggregate and age of samples and, an output parameter which is compressive strength of concrete. The results showed that ANN can be an alternative approach for the predicting the compressive strength of ground granulated blast furnace slag concrete using concrete ingredients as input parameters.
This paper shows results of laboratory study on the effects of nano-SiO2 on Portland cement-fly ash systems. It is aimed to improve performance of fly ash–cement systems, particularly at early age, ...with the inclusion of nano-SiO2. In order to observe the effects of nano-SiO2 particles on the strength and hydration kinetics of fly ash blended cementitious systems, binary and ternary systems were prepared by adding 0.25–1.5% nano-SiO2 by weight of blended cements. Workability, setting time, water absorption capacity, fire resistance, compressive strength and isothermal calorimeter tests were conducted on the cementitious systems. The results indicate that increasing quantity of fly ash increased workability, setting time, water absorption capacity of cementitious systems, whereas the increasing quantity of nano-SiO2 reduced these values. Significant increment in compressive strength were observed, especially at early ages of fly ash–cement systems with nano-SiO2 addition, compared to fly ash added systems, which may compensate for the decrease in compressive strength caused by fly ash. Nano-SiO2 addition accelerated hydration reactions at early age. By partially eliminating the negative effects of fly ash with nano-SiO2, high rates of fly ash can be used in cementitious systems, thus forming more sustainable systems.
•Bond strength and abrasion resistance of alkali activated concretes (AAC) were examined experimentally by CCD method.•AASC were designed and produced considering the SC, SM, CT and ECT as the CCD’s ...independent parameters.•Compressive strength, split tensile strength, ultrasonic pulse velocity (UPV), abrasion and bond behavior of AAC were defined.•Effects of each independent parameter on the dependent parameters were statistically analyzed.•The optimum values of the parameters studied were defined as CT of 66°C, ECT of 14.76h, SC of 5.72% and SM of 1.0 for the defined multi-objective optimization problem.
In this paper, bond strength and abrasion resistance of alkali activated concretes (AAC) were examined experimentally by using the central composite design (CCD) method. AAC were designed and produced considering the sodium concentration (SC), silicate modules (SM), curing temperature (CT) and exposed curing time (ECT) as the CCD’s independent parameters. Twenty-one AAC mixtures were established depend on the various combinations of independent parameters in CCD at 95% confidence level. Effects of each independent parameter on the dependent parameters were statistically analyzed using experimental measurements and best possible combination of the independent parameters were defined for the maximization of the compressive strength, split tensile strength, UPV and bond behavior of AAC and for the minimization of abrasion value of AAC by solving the multi-objective optimization problems which is generated using the proposed regression models for the dependent parameters. Test results demonstrate that all studied independent parameters have the noteworthy effect on the properties of AAC statistically; however, the most effective independent parameter is SC. The optimum values of the parameters studied were defined as CT of 66°C, ECT of 14.76h, SC of 5.72% and SM of 1.0 for the defined multi-objective optimization problem.
This paper reports the results of an investigation on the influences of admixtures and curing conditions on some properties of Alkali-Activated Slag (AAS) mixtures with no cement. In the study, ...Shrinkage-Reducing (SRA) and superplasticizing and setretarding (WRRe) admixtures were used. For the slag activation, sodium metasilicate was used at two sodium concentrations, 4% and 6% by mass of slag. Setting time, flow loss of fresh mixtures, and shrinkage strain, carbonation, flexural and compressive strength of hardened mixtures were measured. The test results showed that the admixtures generally had no impact on the setting times of AAS pastes. WRRe increased the flow rate of AAS mortars while SRA partially affected the flow values of AAS mortars. WRRe and SRA did not produce an important difference on the carbonation depths of AAS mortars. However, WRRe and especially SRA admixtures decreased the shrinkage values of AAS mortars. Additionally, curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to Normal Portland Cement (NPC) mortars, and the strength development of AAS mortars at early ages was very fast in comparison with NPC mortars when subjected to elevated temperature.
This study presents the mechanical and transport properties of milled cut steel fiber reinforced concretes (MCSFRC). Properties studied include unit weight, workability, compressive strength, ...flexural strength, splitting tensile strength, bond strength, water absorption, water porosity, water sorptivity, rapid chloride ion permeability and drying shrinkage of concrete. Mixtures with a waterbinder ratio of 0.40, total binder content of 500 kg/m3 and milled cut steel fiber content of 0, 0.25, 0.50 and 1.00% by concrete volume were produced and tested. The laboratory results showed a slight reduction in compressive strength with the use of milled cut steel fiber. On the other hand milled cut steel fibers significantly improved the tensile strength and decreased the drying shrinkage. Although no significant increase was observed in the absorption, porosity and sorptivity, chloride ion permeability increased drastically with the increase of milled cut steel fiber content.
This paper reports of a comprehensive study on the durability properties of concrete containing polypropylene fiber and fly ash. Properties studied include unit weight and workability of fresh ...concrete, and compressive strength, modulus of elasticity, porosity, water absorption, sorptivity coefficient, drying shrinkage and freeze–thaw resistance of hardened concrete. Fly ash content used in concrete mixture was 0%, 15% and 30% in mass basis, and fiber volume fraction was 0%, 0.05%, 0.10% and 0.20% in volume basis.
The laboratory results showed that inclusion of fly ash improves; however, polypropylene fiber decreases the workability of concrete. Moreover, polypropylene fiber addition, either into Portland cement concrete or fly ash concrete, did not improve the compressive strength and elastic modulus. The positive interactions between polypropylene fibers and fly ash lead to the lowest drying shrinkage of fibrous concrete with fly ash. Freeze–thaw resistance of polypropylene fiber concrete was found to slightly increase when compared to concrete without fibers. Moreover, fly ash increased the freeze–thaw resistance more than the polypropylene fibers did.
