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Effect of Bottom Ash as Fine Aggregate on Shrinkage Cracking of Mortars

The effect of the nonground bottom ash (BA), as fine aggregate in mortar or concrete, on shrinkage cracking is observed on mortar specimens in this study. The replacement was made by weight; the replacement ratios for BA as fine aggregate were 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%. After that, unit weights, ultrasonic pulse velocity, flexural and compressive strengths, and length changes due to free shrinkage were determined by producing 1.58 x 1.58 x 6.3 and 0.984 x 0.984 x 11.22 in. (40 x 40 x 160 and 25 x 25 x 285 mm) prismatic mortar specimens for each series. Furthermore, the modulus of elasticity was also determined by producing 5.91 x 5.91 x 5.91 in. (150 x 150 x 150 mm) cubic mortar specimens. Finally, a ring test was conducted to determine the effect of BA on shrinkage cracking. The widths of the cracks during the ring test were measured using an optical crack microscope. Consequently, it was seen that BA usage up to 100% replacement ratio decreases shrinkage cracking because of the porous structure of mortar specimens related to the coarser structure of BA compared to reference sand. Free shrinkage, however, occurred irregularly. Moreover, the strength and modulus of elasticity also decreased with the increase in BA content due to the same increased porous structure of the mortars containing higher replacement ratios of BA.

Analysis of Rubberized Concrete as a Three-phase Composite Material

Concrete is generally known as a two-phase composite material containing cement matrix and aggregate particles. The effect of transition zone between aggregates and cement paste on compressive strength is well known for traditional concrete but its effect on modulus of elasticity is not yet obvious. İn this study, it is aimed to apply composite material rules on estimating modulus of elasticity of rubberized concrete. İn experimental study, some cylindrical specimens are produced by using waste tire rubber aggregate (RA). RAs replace traditional sand at 15, 30, and 45% ratios by volume. Modulus of elasticity of concrete is determined by conducting experimental test. Hashin—Shtrikman (H—S) bounds are applied and it is attempted to determine whether rubberized concrete match the interval between H—S bounds or not. Consequently, it is indicated that analysis of rubberized concrete as a two-phase material is not corrected by using H—S bounds and it should be considered as a three-phase composite material. İt is also pointed out that transition zone must be considered as the third phase.

Properties of Reinforced Concrete Steel Rebars Exposed to High Temperatures

The deterioration of the mechanical properties of yield strength and modulus of elasticity is considered as the primary element affecting the performance of steel structures under fire. In this study, hot-rolled S220 and S420 reinforcement steel rebars were subjected to high temperatures to investigate the fire performance of these materials. It is aimed to determine the remaining mechanical properties of steel rebars after elevated temperatures. Steels were subjected to 20, 100, 200, 300, 500, 800, and 950∘C temperatures for 3 hours and tensile tests were carried out. Effect of temperature on mechanical behavior of S220 and S420 were determined. All mechanical properties were reduced due to the temperature increase of the steel rebars. It is seen that mechanical properties of S420 steel was influenced more than S220 steel at elevated temperatures.

Effect of Non-Ground-Granulated Blast-Furnace Slag as Fine Aggregate on Shrinkage Cracking of Mortars

This study investigated the effect of non-ground-granulated blast-furnace slag (n-GGBS) as fine aggregate in mortars on shrinkage cracking. The n-GGBS replaced fine aggregate by weight. The replacement ratios ranged from 0-100% in increments of 10%. Unit weight, ultrasonic pulse velocity, flexural strength, compressive strength, and length change due to free shrinkage were determined by producing prismatic mortar specimens for each series. The moduli of elasticity were also determined by producing cubic mortar specimens. The ring test was conducted to determine the effect of n-GGBS on shrinkage cracking. The length and width of the cracks that occurred during the ring test were measured using an optical microscope and a caliper. Consequently, it was observed that the increase in n-GGBS content decreased shrinkage cracking because of the porous structure of mortar specimens related to the structure of n-GGBS. Furthermore, the flexural strength, compressive strength, and modulus of elasticity also decreased for the same reason.

Effect of boron waste on the properties of mortar and concrete

Utilization of by-products or waste materials in concrete production are important subjects for sustainable development and industrial ecology concepts. The usages as mineral admixtures or fine aggregates improve the durability properties of concrete and thus increase the economic and environmental advantages for the concrete industry. The effect of clay waste (CW) containing boron on the mechanical properties of concrete was investigated. CW was added in different proportions as cement additive in concrete. The effect of CW on workability and strength of concrete were analysed by fresh and hardened concrete tests. The results obtained were compared with control concrete properties and Turkish standard values. The results showed that the addition of CW had a small effect upon the workability of the concrete but an important effect on the reduction of its strength. It was observed that strength values were quite near to that of control concrete when not more than 10% CW was used in place of cement. In addition to concrete specimens, replacing cement with CW produced mortar specimens, which were investigated for their strength and durability properties. The tests of SO 4 2- and Cl— effect as well as freeze—thaw behaviour related to the durability of mortar were performed. Consequently, it can be said that some improvements were obtained in durability properties even if mechanical properties had decreased with increasing CW content.

Prediction of restrained shrinkage crack widths of slag mortar composites by Takagi and Sugeno ANFIS models

Abstract Shrinkage is an important parameter affecting crack development of mortars and concrete. With the occurrence of shrinkage cracks, the concrete starts to be exposed to the corrosion which significantly decreases the durability of concrete or mortars. In this study, the results of free shrinkage tests determining the length changes and ring test determination of the restrained drying shrinkage cracks are used for predicting the crack widths of granulated blast furnace slag fine aggregate mortars using adaptive-network-based fuzzy inference system (ANFIS). Subsequently, replacement ratios, drying time and free shrinkage length changes are used as inputs and crack width as output in order to predict the shrinkage cracking of these mortar types. The experimental test and the prediction results from the ANFIS model are compared with each other. It is clear that ANFIS can be employed directly in the prediction or discussion of the drying shrinkage cracks.

Effects of bottom ash and granulated blast furnace slag as fine aggregate on abrasion resistance of concrete

Abstract Abrasion resistance is one of the most important durability properties of concrete. Especially, highway, airport and industrial floor pavements should be resistant to abrasion. Recently, many research studies have been carried out on the utilization of industrial by-products in concrete. Granulated blast-furnace slag (GBFS) and bottom ash (BA) are two of these by-products. BA is not generally utilized in concrete and has a limited usage. It is mostly dumped, leading to additional costs and environmental problems. On the other hand, both GBFS and BA have potential for concrete production to provide sustainability. They can substitute fine aggregate thanks to their positive effects on concrete durability. Therefore, the aim of this study was to investigate the abrasion resistance of concretes produced with GBFS and BA substituting fine aggregate. Three different concrete series were produced by replacing fine aggregate with GBFS, BA and both of them by mixing them at equal ratios. The replacement ratios of by-products were 10%, 20%, 30%, 40% and 50% by volume. Compressive strength and Bohme abrasion tests were conducted on series. Results were compared to each other. It can be said that abrasion resistance can be improved by these by-products.

Improvement of Khorasan mortar with fly ash for restoration of historical buildings

Abstract In this study, the effects of fly ash on Khorasan mortar composed of brick or tile powder and lime were investigated to improve its mechanical properties. In the mixtures, fly ash was used instead of 0- to 4-mm crushed tile or 0- to 1-mm tile powder as aggregate. In addition, slaked lime was used as a binder, and 0–10–20–30–40% fly ash was replaced with crushed tile or tile powder. The consistency, hardened unit weight, ultrasonic pulse velocity, compressive strength and flexural strength before and after exposure to freeze-thaw, and the microstructure and chemical composition of specimens were examined. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and thermogravimetric analysis were conducted on specimens. On the basis of the results, notable improvements were observed in the mechanical properties of specimens with addition of fly ash.

Effect of aggregate type on linear thermal expansion of self-consolidating concrete at elevated temperatures

Abstract In this study, the effects of aggregate type on the coefficient of thermal expansion of self-consolidating concrete (SCC) produced with normal and lightweight (porous) aggregate (SCLC) were investigated. In experiments, three aggregate types, gravel, volcanic tuff, and diatomite, were used. Different combinations of water/cement ratio and superplasticizer dosage levels were prepared for the SCC and SCLC mixtures. Thermal tests were performed to accurately characterize the coefficient of thermal expansion (CTE) of SCC and SCLC aged 28 days using the dilatometer. The CTEs of SCC and SCLC were defined by measuring the linear change in length of concrete specimens subjected to a range of temperatures from 20°C to 1000°C. The results, in general, showed that SCLC has a lower CTE than that of SCC above 100°C. Moreover, CTE values of SCC and SCLC were decreased with increase in porous structure. The aggregate type has significant influence on the thermal properties of SCC.

Effects of Crushed RAP on Free and Restrained Shrinkage of Mortars

Reclaimed asphalt pavement (RAP) is abundant substitute for natural aggregate in many areas. It is obtained by crushing of old road pavements in milling machine during rehabilitation and reconstruction process. In this study, reclaimed asphalt pavement mortars (RAPM) have been produced with different cement dosages and replacement ratios. The destructive and nondestructive tests have been conducted on specimens to determine physical and mechanical properties of RAPM. The free and restrained shrinkage tests on RAPM have been conducted to predict fractural behavior of mortars. The aim of the shrinkage tests was to delay crack formation and improve strain capacity of mortars before cracking. The results showed that RAPM exhibits lower elasticity modulus; however the tensile capacity was improved for deformation before cracking.