Erhan Güneyisi

Recycling ground granulated blast furnace slag as cold bonded artificial aggregate partially used in self-compacting concrete.

Ground granulated blast furnace slag (GGBFS), a by-product from iron industry, was recycled as artificial coarse aggregate through cold bonding pelletization process. The artificial slag aggregates (ASA) replaced partially the natural coarse aggregates in production of self-compacting concrete (SCC). Moreover, as being one of the most widely used mineral admixtures in concrete industry, fly ash (FA) was incorporated as a part of total binder content to impart desired fluidity to SCCs. A total of six concrete mixtures having various ASA replacement levels (0%, 20%, 40%, 60%, and 100%) were designed with a water-to-binder (w/b) ratio of 0.32. Fresh properties of self-compacting concretes (SCC) were observed through slump flow time, flow diameter, V-funnel flow time, and L-box filling height ratio. Compressive strength of hardened SCCs was also determined at 28 days of curing. It was observed that increasing the replacement level of ASA resulted in decrease in the amount of superplasticizer to achieve a constant slump flow diameter. Moreover, passing ability and viscosity of SCCs enhanced with increasing the amount of ASA in the concrete. The maximum compressive strength was achieved for the SCC having 60% ASA replacement.

Effects of end conditions on compressive strength and static elastic modulus of very high strength concrete

The use of bonded and unbonded caps in testing very high strength concrete cylinders has been investigated experimentally. A hundred and ninety-two concrete cylinder specimens of 150-mm diameter and 300-mm height were cast and tested using packing with softboard, neat cement paste, neoprene pad and sulfur mortar. The design strength level of 75–100 MPa was achieved using water-cementitious material ratios of 0.22, 0.26 and 0.31. The results of the study were compared considering compressive strength and static elastic moduli values. A two-way analysis of variance was performed at a .01 level of significance in order to compare the effect of end conditions. It was found that the overall mean compressive strengths of specimens capped with neat cement paste, neoprene pad sulfur mortar were not significantly different. The packed specimens exhibited a significant difference from the others. On the other hand, there was no statistical difference in the static elastic moduli values when different capping types were used. Several modulus prediction equations were also examined. Experimental values were consistently higher than the predicted values.

Permeation Properties of Self-Consolidating Concretes with Mineral Admixtures

This paper addresses the permeation properties of self-consolidating concretes (SCCs) with different types and amounts of mineral admixtures. Portland cement, metakaolin, fly ash, and ground-granulated blast-furnace slag were used in binary, ternary, and quaternary cementitious blends to improve the durability characteristics of SCCs. For this, a total of 22 SCCs were designed that have a constant water-binder ratio (w/b) of 0.32 and a cementitious materials content of 926.75 lb/yd³ (550 kg/m³). In addition to compressive strength and ultrasonic pulse velocity, the permeation resistance of SCCs was determined by means of chloride ion permeability, water permeability, and sorptivity tests. The test results indicated that the permeation properties of SCCs appeared to be very dependent on the type and amount of the mineral admixture used; the SCC mixtures containing metakaolin were found to have considerably higher permeability resistance than the control mixture.

Strength Deterioration of Plain and Metakaolin Concretes in Aggressive Sulfate Environments

This study investigates the effectiveness of metakaolin (MK) on the improvement of durability of concretes to sulfate attack. Experimental parameters of the study were MK replacement levels, water to cementitious materials ratio, initial curing procedure in terms of air curing and water curing, and type of the sulfate exposure regimes such as continuous and drying-immersion cyclic exposures. The degree of sulfate attack was evaluated by the reduction in compressive strength (CS) of concrete. The tests were conducted at specified periods up to 365 days. At the end of initial curing, concrete specimens were divided into three groups such that the first group was transferred into tap water to be used as control in the assessment of CS reduction while the other groups were immersed in 10% Na2 SO4 solution for the period of 365 days under continuous or cyclic exposures. The results indicated that inclusion of MK as modifying agent increased the resistance of concrete against sulfate attack depending mainly on ...

TENSILE BEHAVIOR OF POST-INSTALLED ANCHORS IN PLAIN AND STEEL FIBER-REINFORCED NORMAL- AND HIGH-STRENGTH CONCRETES

The use of anchors for attachments of structural members to concrete come in two general categories: cast-in-place and post-installed. The use of post-installed anchors allows greater flexibility in planning, design, and strengthening of concrete structures. This article reports on a study of the load-deflection behavior of adhesive and grouted anchors embedded in both plain and steel fiber-reinforced normal- and high-strength concretes. The authors tested 12 and 16 mm-diameter adhesive anchors at embedment depths ranging from 40 to 160 mm. Grouted anchors of 16 mm diameter were tested at 80, 120, and 160 mm embedment depths. A total of 57 anchors (39 adhesive and 18 grouted anchors) were tested under monotonic tension loading. Test results showed that pullout capacities of the anchors were not significantly affected by the addition of steel fibers into the concrete. Anchor tests ending with concrete failure resulted in severe damage on plain concrete. With the addition of steel fibers, however, the damage on concrete was significantly reduced. The ultimate capacity of the anchors generally increased with increasing concrete strength. The authors note that current design methods (ACI 349-85 and concrete capacity design [CCD]) overpredicted the pullout capacity as governed by concrete failure.

Properties of Mortars with Natural Pozzolana and Limestone-Based Blended Cements

This paper presents the results of an experimental investigation on the consistency, compressive strength, water sorptivity, chloride ion permeability, electrical resistivity, and sulfate resistance of mortars made with plain and blended cements. Plain (CEM I 42.5 R) and blended cements, including portland pozzolana cements (CEM II A-P 42.5 R and CEM II B-P 32.5 R) and portland limestone cements (CEM II A-LL 42.5 and CEM II B-LL 32.5 R), were used in this study. Mortars with three different water-cement ratios (w/c) of 0.420, 0.485, and 0.550 were produced by using the plain and blended cements. In all the mixtures, the cement:sand ratio was kept constant at 1:2.75 by weight. The compressive strengths of the mortar specimens were tested at 1, 3, 7, 28, 90, and 180 days. Moreover, the water sorptivity, chloride ion permeability, and electrical resistivity of the mortar specimens were measured at 7, 28, 90, and 180 days. The sulfate resistance of the mortars was evaluated by the length change of the mortar specimens up to 30 weeks of exposure. The test results revealed that the use of blended cements decreased the water sorptivity and chloride ion permeability while increasing the electrical resistivity and sulfate resistance of the mortars at later ages compared to the normal portland cements

Performance of self-compacting concrete (SCC) with high-volume supplementary cementitious materials (SCMs)

Abstract: Since ordinary self-compacting concrete (SCC) is usually associated with high material costs due to its high binder and chemical admixture content, researchers are currently attempting to produce SCC with high volumes of supplementary cementitious materials (SCMs), to make it cost effective and more durable. The SCMs used in this type of SCC, namely fly ash (FA), ground-granulated blast furnace slag (GGBFS), silica fume (SF), metakaolin (MK) etc., are generally industrial by-products and waste materials. A subsidiary effect of this SCC composition is to conserve the environment and non-renewable natural material resources. This chapter reviews the current literature on fresh properties of SCC containing high-volume SCMs, and explains the effect of high-volume SCMs on the mechanical and durability-related properties of SCC.

Durability and Shrinkage Characteristics of Self-Compacting Concretes Containing Recycled Coarse and/or Fine Aggregates

This paper addresses durability and shrinkage performance of the self-compacting concretes (SCCs) in which natural coarse aggregate (NCA) and/or natural fine aggregate (NFA) were replaced by recycled coarse aggregate (RCA) and/or recycled fine aggregate (RFA), respectively. A total of 16 SCCs were produced and classified into four series, each of which included four mixes designed with two water to binder (w/b) ratios of 0.3 and 0.43 and two silica fume replacement levels of 0 and 10%. Durability properties of SCCs were tested for rapid chloride penetration, water sorptivity, gas permeability, and water permeability at 56 days. Also, drying shrinkage accompanied by the water loss and restrained shrinkage of SCCs were monitored over 56 days of drying period. Test results revealed that incorporating recycled coarse and/or fine aggregates aggravated the durability properties of SCCs tested in this study. The drying shrinkage and restrained shrinkage cracking of recycled aggregate (RA) concretes had significantly poorer performance than natural aggregate (NA) concretes. The time of cracking greatly prolonged as the RAs were used along with the increase in water/binder ratio.

Internal Curing of High-Strength Concretes Using Artificial Aggregates as Water Reservoirs

This paper investigates the shrinkage cracking performance of high-strength concrete (HSC) containing artificial fly ash (AFA) and artificial blast furnace slag aggregates (ASAs) used as water reservoirs to provide internal curing. Artificial aggregates (AAs) were produced through cold bonding pelletization of 90% fly ash or slag with 10% portland cement. At a constant water-cement ratio (w/c) of 0.28, a total of nine HSCs incorporating varying amounts of AFA or ASA (0%, 5%, 10%, 15%, and 20%) by total aggregate volume were designed. The hardened concretes were tested for compressive strength, splitting tensile strength, and modulus of elasticity at 28 days for assessment of mechanical properties. Drying shrinkage accompanied by water loss, restrained shrinkage, and autogenous shrinkage were also monitored for a drying period of 57 days. Test results indicated that the highest mechanical properties were achieved for HSC with 20% ASA. Using ASA extended the cracking time of the HSCs and resulted in finer cracks associated with the lower free shrinkage. Moreover, there was a marked decrease in the autogenous shrinkage for all HSCs including artificial aggregates.

Combined Use of Natural and Artificial Slag Aggregates in Producing Self-Consolidating Concrete

This study addresses properties of self-consolidating concrete (SCC), in which natural coarse aggregates had been substituted by artificial slag aggregates (ASAs). For this, 90% groundgranulated blast-furnace slag and 10% portland cement by weight were pelletized in a tilted pan through cold-bonded agglomeration process. Then, the hardened coarse aggregates (ASA) were tested for specific gravity, water absorption, and crushing strength. Thereafter, they were partially used in producing SCCs in which ASA replaced the natural coarse aggregates at 0, 20, 40, 60, 80, and 100% by volume. Therefore, six SCCs with 0.32 water-binder ratio (w/b) were designed and cast using both natural and/or ASA. Hardened concrete properties were tested for compressive and splitting tensile strengths, modulus of elasticity, drying shrinkage, freezing-andthawing resistance, chloride ion permeability, gas permeability, and sorptivity. Test results indicated that SCCs with ASA displayed better performance than the control mixture in terms of durability-related properties. Incorporating ASA in SCCs increased the compressive strength and elastic modulus (up to 60%) but decreased the splitting tensile strength. However, ASA provided gradual reduction in sorptivity coefficient, chloride ion, and gas permeability especially at 60% replacement level and 56 days.