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.
The influence of nano SiO2(NS) and CaCO3(NC) particles on the properties of class F fly ash based geopolymer mortar activated with different sodium ion concentrations have been investigated. Mortar ...mixture proportions were 1:3:0.3 for binder, sand, and water, respectively. Nano SiO2 and CaCO3 particles were replaced with a binder by weight basis at the ratios of 1, 2, and 3% in the mixtures. Sodium concentrations amount used were 8, 10, and 12% Na+ of binder content. Geopolymer mortar samples were cured at 60, 75, and 90°C in a furnace for 24, 48, and 72 hr. After the heat curing process, flexural, and compressive strength tests were performed. The changes in the microstructure of geopolymer due to influence of nanoparticles were examined by utilizing isothermal calorimetric studies on geopolymer paste, and field‐emission scanning electron microscopy (FESEM). Based on laboratory work results, it was concluded that for all sodium ion concentrations, the addition of nano SiO2 and CaCO3 particles improved the flexural and compressive strengths after 24 hr heat curing. However, the favorable effects of nanoparticles on strength properties tend to disappear after 48 and 72 hr heat curing. The results of isothermal calorimetric studies showed that nano SiO2 and CaCO3 particles accelerated the geopolymeric reactions at an early age. FESEM results showed that additions of nanoparticles made the microstructure of geopolymer products more intense and compact.
A laboratory investigation was carried out to evaluate the strength properties of high-volume fly ash (HVFA) roller compacted and superplasticised workable concrete cured at moist and dry curing ...conditions. Concrete mixtures made with 0%, 50% and 70% replacement of normal Portland cement (NPC) with two different low-lime Class F fly ashes, good and low quality, were prepared. Water–cementitious material ratios ranged from 0.28 to 0.43. The compressive, flexural tensile and cylinder splitting tensile strengths were measured and presented. The relationship between the flexural tensile and compressive strengths was discussed. The influence of loss on ignition (LOI) content of fly ash on water demand and the strength of concrete was also discussed. The influence of moist and dry curing conditions on the high-volume fly ash (HVFA) concrete system was assessed through a proposed simple efficiency factor. The study showed that producing high-strength concrete was possible with high-volume fly ash content. LOI content increased the water demand of fresh concrete. HVFA concrete was found to be more vulnerable to dry curing conditions than was NPC concrete. It was concluded that HVFA concrete was an adequate material for both structural and pavement applications.
•Transport properties of class F fly ash based geopolymer were investigated.•Influence of activator type and amount on transport properties of geopolymer were reported.•The best results were obtained ...at %15 Na ratios for all transport characteristics.•The findings could help for selection of Na ratio and activator type for geopolymers.
It is known that transport properties of porous materials were important in terms of its durability aspect. In this paper, the effect of activator type, Na amount on the transport properties of geopolymer mortar made with class F fly ash were explored. Two different class F fly ash were employed in producing geopolymer that activated alkaline solutions. As alkali activator, sodium hydroxide solution, and combination of sodium silicate with sodium hydroxide were used. Activator contained 6%, 9%, 12% and 15% of fly ash weight as Na amount. Heat curing regimes were imposed to specimens at 100 °C temperature for 24 h duration. Tests were carried out on the geopolymer samples including water absorption, volume of permeable voids, sorptivity, depth of penetration of water under pressure, chloride ion penetration and accelerated corrosion. It is found that the transport properties of geopolymer samples are improved by increasing the Na amounts of mortar mixtures from 6% to 15%. In general, better results were obtained with 15% Na ratio. The mortars produced with only sodium hydroxide have shown better transport properties than mortars made with combination of sodium hydroxide-sodium silicate mixture.
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.
This paper reports on a comprehensive study on the properties of concrete containing fly ash and steel fibers. Properties studied include unit weight and workability of fresh concrete, and ...compressive strength, flexural tensile strength, splitting tensile strength, elasticity modulus, sorptivity coefficient, drying shrinkage and freeze–thaw resistance of hardened concrete. Fly ash content used was 0%, 15% and 30% in mass basis, and fiber volume fraction was 0%, 0.25%, 0.5%, 1.0% and 1.5% in volume basis. The laboratory results showed that steel fiber addition, either into Portland cement concrete or fly ash concrete, improve the tensile strength properties, drying shrinkage and freeze–thaw resistance. However, it reduced workability and increase sorptivity coefficient. Although fly ash replacement reduce strength properties, it improves workability, reduces drying shrinkage and increases freeze–thaw resistance of steel fiber reinforced concrete. The performed experiments show that the behaviour of fly ash concrete is similar to that of Portland cement concrete when fly ash is added.
•Using RW and EP reduced the unit weight and UPV values of geopolymer mortars.•RW and EP increased absorption, porosity, and thermal insulation of mortar.•RW and EP reduced the flexural and ...compressive strengths of geopolymer mortars.•Using RW and EP increased the thermal resistance of geopolymer mortar.•Perlite could be a feasible alternative for green thermal insulating material.
It is known that studies on lightweight geopolymer using fly ash need more research. Therefore, in this study, class F fly ash-based lightweight geopolymer mortar samples were produced by using river sand, raw perlite, and expanded perlite as aggregates. The study was planned in two groups. In the first group, river sand, raw perlite, and expanded perlite were used as aggregates. In the second group, raw perlite and expanded perlite were used as aggregates. Expanded perlite replacement rates in both groups were determined as 0%, 20%, 40%, 60%, 80%, and 100%. The produced geopolymer mortar samples were cured at 75 °C for 24 and 48 h. After heat curing, unit weight, ultrasonic pulse velocity, water absorption, porosity, thermal conductivity coefficient, and flexural and compressive strength tests were performed on the samples. In addition, the elevated temperature resistance of the geopolymer mortar samples was tested at 300 °C, 600 °C, and 900 °C temperatures. Moreover, the microstructures of geopolymer mortar samples before and after elevated temperature were examined using a field emission scanning electron microscope. According to the results obtained, with the use of raw and expanded perlite, unit weight, UPV, flexural and compressive strengths of geopolymer mortar samples decreased, while water absorption and porosity increased. Using raw and expanded perlite resulted in an increase in the thermal insulation performance of the geopolymer mortar samples. Furthermore, the use of expanded perlite in geopolymer mortar samples increased the strength of geopolymer mortar samples exposed to elevated temperatures of 900 °C.
► The use of GBFS increased the compressive strength of waste PET lightweight aggregate (WPLA) mortars. ► Using decreased the compressive strength values of WPLA mortars compared to cement and GBFS ...modified samples. ► GBFS and FA replacement reduced the drying shrinkage values of WPLA mortars. ► GBFS and FA replacement increased the carbonation depths of WPLA mortar samples.
In this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4
mm. The waste lightweight PET aggregate (WPLA)–binder ratio (WPLA/
b) was 0.60; the water–binder (
w/
b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural–tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90
days) of the WPLA mortars. However, FA substitution decreased compressive and flexural–tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects.
► Compressive and flexural strength increased with the Na dosage in the mix. ► An increase in the replacement level of GGBS increased the strength of the mortars. ► Carbonation values of the mortars ...decreased with the increase of activator dosage. ► The exploitation of GGBS can lead to a considerable economic benefit.
The aim of the present study is to investigate some properties of alkali-activated mortars containing slag at different replacement levels. Ground granulated blast furnace slag was used at 0%, 20%, 40%, 60%, 80% and 100% replacement by weight of cement, and liquid sodium silicate having three different Na dosages was chosen as the alkaline activator. In this research, carbonation resistance measurements and compressive and flexural strength tests were performed on the mortar specimens with size of 40
×
40
×
160
mm. The findings obtained from the tests showed that carbonation depth values of the mortars decreased with the increase of activator dosage. Additionally, compressive and flexural strength values increased with the increase in activator concentration and slag replacement level. Portland cement/slag mortars activated by liquid sodium silicate exhibited lower strength than the slag alone activated by the same activator.
In this study, the influence of waste PET as lightweight aggregate (WPLA) replacement with conventional aggregate, on thermal conductivity, unit weight and compressive strength properties of concrete ...composite was investigated. For this purpose, five different mixtures were prepared (the control mixtures and four WPLA mixtures including 30%, 40%, 50%, and 60% waste PET aggregate by volume). Thermal conductivity (TC) coefficients of the specimens were measured with guarded hot plate apparatus according to TS ISO 8302 1. The thermal conductivity coefficient, unit weight and compressive strength of specimens decreased as the amount of WPLA increased in concrete. The minimum thermal conductivity value was 0.3924W/mK, observed at 60% WPLA replacement. From this result, it was concluded that waste PET aggregates replacement with conventional aggregate in the mixture showed better insulation properties (i.e. lower thermal coefficient). Due to the low unit weight and thermal conductivity values of WPLA composites, there is a potential of using WPLA composites in construction applications.
