Effect of Granulated Blast Furnace Slag and fly ash addition on the strength properties of lightweight mortars containing waste PET aggregates

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.     

Utilization of beet molasses as a grinding aid in blended cements

This paper investigates the viability of using beet molasses as a grinding aid for blended cements with high volumes of mineral admixtures. Different ratios of beet molasses (0.01–0.05% by weight of cement) were added into a blended cement containing 41% of fly ash and GBFS. The influence of beet molasses on performances of blended cement was studied by comparing with one commercially available, triethanolamine-based grinding aid (TA). The results show that when comparing with the blank cement mixture, the cement containing 0.02–0.03% molasses shows a higher compressive strength at 3 days and 28 days, even exceeding the TA mixture. The improved microstructure of the molasses modified cement paste was also demonstrated by the pore structure and SEM measurements. These improvements are attributed to the better particle size distribution induced by the addition of molasses, indicating the potential application of beet molasses as a good grinding aid.     

Characterization of marble powder for its use in mortar and concrete

A powder obtained as a by-product of marble sawing and shaping was characterized from a chemical and physical point of view in order to use it as mineral addition for mortars and concretes, especially for self-compacting concrete. This marble powder showed a very high Blaine fineness value of about 1500 m²/kg, with 90% of particles finer than 50 μm and 50% under 7 μm. For rheological studies, several cement pastes were prepared using marble powder, with and without the addition of an acrylic-based superplasticizer. Water to cementitious materials ratio was also varied. In order to evaluate the effects of the marble powder on mechanical behaviour, many different mortar mixtures were tested, all prepared with sand to cement ratio of 3:1 at about the same workability. Mixtures were evaluated based upon cement or sand substitution by the marble powder. Results obtained show that 10% substitution of sand by the marble powder provided maximum compressive strength at about the same workability.     

Development of alpha plaster from phosphogypsum for cementitious binders

Efforts have been made to make high strength alpha plaster from phosphogypsum, a by-product of phosphoric acid industry. Phosphogypsum was autoclaved in slurry form (phosphogypsum 50% + water 50%, by wt.) in the laboratory at different steam pressures for different durations in presence of chemical admixtures. It was found that with small quantity of chemical admixture (sodium succinate/potassium citrate/sodium sulphate), alpha plaster of high strength can be produced. The optimum pressure and duration of autoclaving was found to be as 35 psi and 2.0 h, respectively. The alpha plaster was examined for making cementitious binders by admixing hydrated lime, fly ash, granulated blast furnace slag, marble dust and chemical additives with alpha plaster. Data showed that cementitious binder of compressive strength of 22.0 and 30 MPa (at 28 days of curing at 40° and 50 °C) and low water absorption was produced. DTA and SEM studies of the binder showed formation of CSH, ettringite and C₄AH₁₃ as main cementitious products to give strength.     

Oil palm shell as a lightweight aggregate for production high strength lightweight concrete

In Malaysia, oil palm shell (OPS) is an agricultural solid waste originating from the palm oil industry. In this investigation old OPS was used for production of high strength lightweight concrete (HSLC). The density, air content, workability, cube compressive strength and water absorption were measured. The effect of five types of curing conditions on 28-day compressive strength was studied. The test results showed that by incorporating limestone powder and without it, it is possible to produce the OPS concretes with 28-day compressive strength of about 43–48 MPa and dry density of about 1870–1990 kg/m³. The compressive strength of OPS HSLC is sensitive to the lack of curing. The water absorption of these concretes is in the range of good concretes.     

Influence of high temperature on the properties of concretes made with industrial by-products as fine aggregate replacement

Influence of high temperature on the properties of concrete containing non-ground granulated blast-furnace slag (GBFS) and coal bottom ash (BA) as fine aggregate was presented. Six series of concrete mixtures were prepared by partially replacing fine aggregate separately with GBFS and BA. Replacement percentages were between 10 and 50% with an increment of 10% by dry weight of fine aggregate. Then 0.2% polypropylene fibres (PP) were added to last three mixtures that has the same mixture with the first three series. The first series is control concrete, the second series contained GBFS and the third series contained BA. All the concrete specimens were exposed to 800 °C temperature at the age of 90 days. Tests were conducted to determine loss in weight, compressive strength, and dynamic modulus of elasticity. Also surface crack observations were conducted with microscope. Test results showed that it is possible to partially replace fine aggregate with GBFS or BA even if such concretes were to be subjected to high temperature response. Performance of BA concrete was found to be better than GBFS as replacement material.     

骨料对自密实混凝土性能的影响

研究了粗骨料最大粒径、粗骨料级配、砂率等因素对掺不同矿物掺合料,如粉煤灰、矿渣粉或硅灰的自密实混凝土的工作性与强度性能的影响。试验结果表明,粗骨料最大粒径越小,自密实混凝土的流动性越大、粘聚性越好。随着粉煤灰、矿渣粉的掺量增大,自密实混凝土的流动性明显增大,粘聚性显著下降。复合掺入合适比例的矿物掺合料,可有效改善自密实混凝土工作性与强度。粗骨料级配是影响自密实混凝土性能的重要因素之一。随着砂率增大,自密实混凝土拌合物的流动性增大,粘聚性减小,流动性损失减小,早期和后期抗压强度也随之下降。     

Assessment of the effects of rice husk ash particle size on strength,water permeability and workability of binary blended concrete

This study develops the compressive strength, water permeability and workability of concrete by partial replacement of cement with agro-waste rice husk ash. Two types of rice husk ash with average particle size of 5 micron (ultra fine particles) and 95 micron and with four different contents of 5%, 10%, 15% and 20% by weight were used. Replacement of cement up to maximum of 15% and 20% respectively by 95 and 5 μm rice husk ash, produces concrete with improved strength. However, the ultimate strength of concrete was gained at 10% of cement replacement by ultra fine rice husk ash particles. Also the percentage, velocity and coefficient of water absorption significantly decreased with 10% cement replacement by ultra fine rice husk ash. Moreover, the workability of fresh concrete was remarkably improved by increasing the content of rice husk ash especially in the case of coarser size. It is concluded that partial replacement of cement with rice husk ash improves the compressive strength and workability of concrete and decreases its water permeability. In addition, decreasing rice husk ash average particle size provides a positive effect on the compressive strength and water permeability of hardened concrete but indicates adverse effect on the workability of fresh concrete.     

Assessing of the fresh concrete properties of self-compacting concrete containing sawdust ash

Evaluation of self-compactability of SCC mixes containing SDA as powder material and naphthalene sulphonate (NS) and melamine sulphonate (MS), respectively, shows that optimum workability range for the slump flow test lie between 665 mm and 680 mm, while the V-funnel test is 8.2 s and 8.4 s. These values show that adequate mix stability and self deaeration are achieved. Results of the self-compactability of the SCC mixes using the U- and L-box are within the targets and tolerance values stipulated by EFNAC (2002). These are 28.5 mm/29 mm and 0.85/0.85, respectively, for mix containing NS and MS.     

Effect of waste marble dust content as filler on properties of self-compacting concrete

Day by day, the amount of the marble dust (MD) as a waste material is significantly of increasing in Turkey. Therefore, the utilization of the waste MD in self-compacting concrete (SCC), as filler material, is the main objective of this study. Besides, the MD is used directly without attempting any additional process. Thus, this would be another advantage for this objective. For this purpose, MD has replaced binder of SCC at certain contents of 0, 50, 100, 150, 200, 250 and 300 kg/m³. After then, slump-flow test, L-box test and V-funnel test are conducted on fresh concrete. Furthermore, compressive strength, flexural strength, ultrasonic velocity, porosity and compactness are determined at the end of 28 days for the hardened concrete specimens. The effect of waste MD usage as filler material on capillarity properties of SCC is also investigated. According to the test results, it is concluded that the workability of fresh SCC has not been affected up to 200 kg/m³ MD content. However, the mechanical properties of hardened SCC have decreased by using MD, especially just above 200 kg/m³ content.     

The properties of concrete made with fine dune sand

This paper presents the results of a study that investigated the properties of concrete made with dune sand. Different control concrete mixtures using ordinary Portland cement (OPC) with a minimum design compressive strength of 40 N/mm² were prepared. The amount of fine aggregates constituted about 36% by weight of all the aggregates. The workability ranged from low of 16 mm to a high of 122 mm. For each control mix, other mixtures were prepared in which the fine aggregates were replaced by different percentages of dune sand ranging from 10% to 100%. The effect of dune sand on the workability, compressive strength, tensile strength, modulus of elasticity and initial surface absorption test (ISAT) was studied. Experimental results show an improvement in the workability of concrete when fine aggregates were partially replaced by dune sand. An increase in slump was measured with increase in dune sand content. However, at high dune sand contents (above 50%); the slump starts to decrease with an increase in dune sand. Generally, the strength values decrease with increase in dune sand replacement. The strength loss was not found considerable as the maximum reduction was less than 25% when fine aggregates were fully replaced by dune sand. The absorption characteristics of concrete made with OPC as measured by the (ISAT) generally increased with higher dune sand contents.     

Properties of self-compacting concretes made with binary,ternary, and quaternary cementitious blends of fly ash,blast furnace slag,and silica fume

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/m³. 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.     

Composition,strength and workability of alkali-activated metakaolin based mortars

This study has investigated the joint effect of several factors on the workability and mechanical strength of alkali-activated metakaolin based mortars. The factors analysed through a laboratory experiment of 432 specimens, pertaining to 48 different mortar mixes were, sodium hydroxide concentration (10 M, 12 M, 14 M, 16 M), the superplasticizer content (1%, 2%, 3%) and the percentage substitution of metakaolin by calcium hydroxide in the mixture (5%, 10%). The results show that the workability decreases with the concentration of sodium hydroxide and increases with the amount of calcium hydroxide and superplasticizer. The results also show that the use of 3% of superplasticizer, combined with a calcium hydroxide content of 10%, allows improving the mortar flow from less than 50% to over 90%, while maintaining a high compressive and flexural strength.     

Influence of activator on the strength and drying shrinkage of alkali-activated slag mortar

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.     

Metakaolin,a solution for the precast industry to limit the clinker content in concrete: Mechanical aspects

The current trend to decrease the clinker content in cements through the use of mineral additions in order to limit CO₂ emissions into the atmosphere is of major concern for the precast industry as the resulting binders are generally not very reactive at early ages. Here, composed cements (clinker + slag) or combinations between clinker and mineral admixtures are studied with a view to investigating the compressive strength of cement-based materials at both early (1 day) and later (28 days) ages under steam curing conditions. Limestone and siliceous fillers, silica fume and four metakaolins differing in their production process and impurity content were investigated. Considering performance, economic and environmental criteria, results in the laboratory showed that metakaolin (MK) is a very promising solution at a clinker replacement rate of 12.5–25% by mass. Compressive strength was significantly increased (1-day age) or practically the same as for reference mortars incorporating cement only (28-day age). Thus, in comparison with a reference concrete containing no MK and for an identical granular skeleton, the combination clinker/MK was validated in the precast factory in full-scale trials for slip-forming (25% replacement) and self-compacting (17.5% replacement) concrete applications: compressive strength and porosity were not affected.     

Effect of slag on the rheology of fresh self-compacted concrete

The building industry is turning increasingly to the use of self-compacting concrete (SCC) in order to improve many aspects of building construction as SCC offers several advantages in technical, economic, and environmental terms. Fresh self-compacting concrete (SCC) flows into place and around obstructions under its own weight to fill the formwork completely and self-compact without any segregation and blocking. SCC mixes generally have a much higher content of fine fillers. The use of supplementary cementitious materials is well accepted because of the improvement in concrete properties and also for environmental and economical reasons. The present paper is an effort to quantify the influence of Algerian slag on the properties of fresh and hardened self-compacting concrete. The workability-related fresh properties of SCC were observed through slump flow time and diameter, V-Funnel flow time, J-Ring test, U-Box filling height and GTM sieve stability test. The only hardened property that was included in this study was the compressive strength. An optimum slag content of 15% seems to give a good SCC mixture with workability retention of about 60 min. A decrease in compressive strength with increase of slag content was obtained, but this decrease in compressive strength is less important at late ages (56 and 90 days after mixing).     

Effect of elevated temperature on the mechanical properties of concrete produced with finely ground pumice and silica fume

This study investigated the effect of elevated temperature on the mechanical and physical properties of concrete specimens obtained by substituting cement with finely ground pumice (FGP) at proportions of 5%, 10%, 15% and 20% by weight. To determine the effect of silica fume (SF) additive on the mechanical and physical properties of concrete containing FGP, SF has been added to all series except for the control specimen, which contained 10% cement by weight instead. The specimens were heated in an electric furnace up to 400, 600 and 800 °C and kept at these temperatures for one hour. After the specimens were cooled in the furnace, ultrasonic pulse velocity (UPV), compressive strength and weight loss values were determined. The results demonstrated that adding the mineral admixtures to concrete decreased both unit weight and compressive strength. Additionally, elevating the temperature above 600 °C affected the compressive strength such that the weight loss of concrete was more pronounced for concrete mixtures containing both FGP and SF. These results were also supported by scanning electron microscope (SEM) studies.     

Utilization of Rice Husk Ash as viscosity modifying agent in Self Compacting Concrete

Self Compacting Concrete (SCC) is defined by two primary properties: Deformability and Segregation resistance. Deformability or flowability is the ability of SCC to flow or deform under its own weight (with or without obstructions). Segregation resistance or stability is the ability to remain homogeneous while doing so. High range water reducing admixtures are utilized to develop sufficient deformability. At the same time, segregation resistance is ensured, which is accomplished either by introducing a chemical viscosity modifying admixture (VMA) or by increasing the amount of fines in the concrete. These viscosity modifying admixtures are very expensive and the main cause of increase in the cost of SCC. Therefore, for producing low cost SCC, it is prudent to look at the alternates to help reducing the SSC cost. This research is aimed at evaluating the usage of Rice Husk Ash (RHA) as viscosity modifying agent in SCC, and to study the relative costs of the materials used in SCC.In this research, the main variables are the proportion of RHA, dosage of superplasticizer for flowability and water/binder ratio. The parameters kept constant are the amount of cement, water, fine and coarse aggregate contents.Test results substantiate the feasibility to develop low cost SCC using RHA. In the fresh state of concrete, the different mixes of concrete have slump flow in the range of 595–795 mm, L-box ratio ranging from 0 (stucked) to 1 and flow time ranging from 2.2 to 29.3 s. Out of nine mixes, four mixes were found to satisfy the requirements suggested by European federation of national trade associations representing producers and applicators of specialist building products (EFNARC) guide for making SCC. The compressive strengths developed by the SCC mixes with RHA were comparable to the control concrete. Cost analysis showed that the cost of ingredients of specific SCC mix is 42.47% less than that of control concrete.     

Development and characterization of an inorganic foam obtained by using sodium bicarbonate as a gas generator

In the construction industry almost all of the insulating and expansive materials are organic foams. In this work, the production of an inorganic foam is described. Sodium bicarbonate is used as a gas generator. CO₂ gas is released when water is added to the mixture of sodium bicarbonate and β-hemihydrate gypsum powder (CaSO₄ · 1/2H₂O). Hence, stabilization of the foam is achieved when CO₂ gas is released and water is absorbed by β-hemihydrate gypsum powder, which subsequently is converted into calcium sulphate dihydrate (gypsum matrix). The bulk density and mechanical properties (compressive and flexural strength) of the inorganic foam and gypsum were determined. Microstructural characterization has been carried out by SEM and XRD, and a new sodium sulphate phase was identified in the gypsum foam due to this chemical reaction. Finally, thermal properties such as thermal conductivity and diffusivity were measured and it was observed how for the same heat flux, the thickness of an inorganic foam slab is 73.4% less than that of a concrete slab.     

Properties of self-compacting concrete mixtures containing metakaolin and blast furnace slag

Rheological, mechanical and durability properties of self-compacting concrete (SCC) mixes produced using blended binders containing metakaolin and blast furnace slag are studied. The rheological properties of SCC mix with metakaolin are characterized by significant yield stress and relatively low viscosity, while the mix with blast furnace slag shows zero yield stress and higher viscosity. The compressive strength of SCC with metakaolin grows very fast during the initial hardening period and remains significantly higher, as compared with the mix with blast furnace slag, up to 90 days. Durability properties of the mix containing metakaolin are excellent. Water absorption coefficient and water penetration depths are very low. The freeze resistance tests show zero mass loss after 56 cycles in deicing salt solution.