Compression toughness tests were carried out on concrete cylinders reinforced with three different aspect ratios of hooked-end steel fibers 60, 75, and 83 and six different percentages of steel fibers 0.5, 1.0, 1.25, 1.5, 1.75, and 2.0% by volume of concrete. The w/c ratio used for the normal strength steel fiber reinforced concrete mixes (NSSFRC) was 0.55, and the water-cementitious ratio (w/c+s) for the high strength fiber reinforced concrete mixes (HSSFRC) was 0.31. For each mix, three test cylinders were tested for compression specific toughness. The effect of fiber reinforcement index: volume of fibers × length/diameter ratio on compression specific toughness and also on the relationship between these two properties is presented in this paper. As a result, (a) equations are proposed to quantify the effect of fibers on compression toughness ratio of concrete in terms of FRI, (b) equations obtained in terms of FRI and compression specific toughness of plain concrete to estimate both compression specific toughness of NSSFRC and HSSFRC (N.m), (c) equations obtained which represent the relationship between compression toughness index and FRI for NSSFRC and HSSFRC, respectively, and (d) equations obtained to quantify the relationship between compression specific toughness index and fiber reinforcement index for NSSFRC and HSSFRC, respectively. The proposed equations give good correlation with the experimental values.
This paper investigates the effects of cement content and water/cement ratio on workable fresh concrete properties with slump changing between 90 to 110 mm, and determines the relations among fresh concrete properties such as slump, compacting factor, VeBe, unit weight and setting times of mortar with temperature history. The experiments were conducted under laboratory conditions on eight different concrete mixtures prepared from ordinary Portland cement (cement contents of 300, 350, 400, 450, 500, 550, 600 and 650 kg/m3) and crushed limestone coarse and fine aggregates. Relations such as (a) VeBe time/unit weight/slump/K-slump/compacting factor/w/c ratio for cement content, (b) K-slump/compacting factor/unit weight/VeBe time for slump, (c) aggregate/cement ratio/unit weight/VeBe time for compacting factor, and (d) penetration resistance for elapsed time were determined. It was observed that increasing the cement content causes increase in the slump, K-slump, compacting factor and fresh concrete unit weight, and reduces VeBe time. Proposed fresh concrete relationships are quite appropriate for concretes without using any mineral or chemical admixtures. Key words: Fresh concrete, slump, compacting factor, VeBe time, unit weight, setting time.
Permeability plays a crucial role in determining the durability of concrete structures, particularly their susceptibility to corrosion. This study explores the potential of sulfur concrete as a protective insulator for concrete surfaces. A comparative analysis is conducted to assess the permeability of sulfur concrete (SC), conventional concrete covered with 1 mm sulfur cover (CC-SC), and conventional Portland cement concrete (CC). The investigation includes evaluations of water absorption, void percentage, and accelerated corrosion tests. The time taken for crack initiation and propagation to reach a 1 mm width is recorded. The results demonstrate that sulfur concrete exhibits lower porosity and water absorption, highlighting its waterproof properties and ability to reduce permeability. Significantly, sulfur concrete effectively blocks current flow in the accelerated corrosion test, acting as an insulating barrier. Additionally, cracks in the Portland cement concrete specimens appear after 6 and 9 days for initial crack formation and a 1 mm crack width, respectively. However, when a 1 mm sulfur layer is applied to the surface of the Portland cement concrete, the first crack occurs after 7 days, with a 1 mm crack width observed after 12 days. This indicates that the sulfur cover provides protection for the reinforced concrete and delays the corrosion process. It is important to note that although the sulfur cover delays corrosion in Portland cement concrete, it does not entirely prevent it. Further research and the implementation of additional preventive measures are recommended to address this limitation and enhance corrosion resistance.
The main disadvantage of high-strength concrete is its highly brittle behavior and this can beovercome by adding fibers to the concrete. This would also improve some other mechanical properties of high-strength concrete such as tensile strength and compressive strength. These properties are not very well established for high-strength steel-fiber reinforced concrete (HSFRC) yet. In this study the influence of silica fume on the properties of HSFRC were investigated by using silica fume of two different percentages and three different hooked-end fibers namely, 30/0.50, 60/0.80 and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different volume percentages of 0.5, 1.0 and 2.0 by volume of concrete. The results indicated that there is a linear function between splitting tensile strength (F splt) and volume percentage of fibers (V f) [i.e. F plt = A(V f) + B, where A and B are correlation coefficients] as well as between splitting tensile strength (F splt) and compressive strength (F c) of plain series A concrete [i.e. F splt = C (√F c) + D, where C and D are correlation coefficients]. These relations can describe the development of splitting tensile strength of HSFRC containing no silica fume, 5% silica fume and 10% silica fume by weight of cement. On the other hand, although silica fume has an effect on compressive strength, volume percentage and aspect ratio of steel fibers has little effect.
In this lecture note it has been tried to gather a lot of data about advanced materials of construction in different aspect.
Copper mining and processing activities at an abandoned mine in the Lefke-Xeros area of Cyprus have created a huge environmental contamination problem in the locality. As an alternative mitigation and management measure, we reported in previous studies that these tailings could be used as a concrete making material. In this paper, results of an experimental investigation of the reinforcement corrosion performance and cost efficiency of 0.57 and 0.50 w/b ratio concrete containing copper tailings either as a cement replacement or an additive material are presented. The time to initiation of corrosion and half-cell potential (HCP) of reinforcements were measured. Actual corrosion status of extracted reinforcement bars was also verified by visual inspection. Results showed that while early corrosion initiation occurred in some samples containing tailings as a cement replacement material, delayed corrosion initiation was observed in all samples containing copper tailings as an additive. Although HCP values became slightly more electronegative as tailings content of samples increased, no substantial reinforcement corrosion was observed. Based on corrosion performance and cost efficiency analyses, utilization of 5% pre-wetted tailings either as a cement replacement or an additive material is the best tailings reuse approach. Increased tourism-related businesses associated with reduced pollution of the Lefke-Xeros coastal area would have a positive impact on the socioeconomic status of the community.
The main objective of this study was to assess and identify general construction faults and to investigate the effects of construction faults on the linear performance levels of reinforced concrete buildings. For doing this, observed two common construction faults (i.e., corrosion and honeycombing) were considered to be used in linear performance analyses. Finite element method was used to model the honeycombing at the column-beam joints. The effects of corrosion on the performance levels were ensured by reducing the cross-sectional area of reinforcement bars and reduced concrete compressive strength as a function of corrosion rate. Thus, two different construction faults on the levels of structural performance were discussed and compared. The results showed that the effects of honeycombing on performance levels of reinforced concrete building with linear performance analyses was more dramatic when it was compared with the results of damage building due to corrosion having a moderate to high corrosion threshold.
Effects of crusher dust content in aggregate on properties of fresh and hardened concrete are not very well known. On the other hand, it is known that short discrete fibers delay the propagation of microcracks and improve some properties of concrete. In this research, the effect of crusher dust replacement levels of fine aggregate and hooked-end steel fibers with different aspect ratios and different volumes on some properties of concrete was investigated. All mixes were tested for compressive and splitting tensile strength, water penetration, flexural toughness energy and impact energy. Relations such as compressive strength/splitting tensile strength/water penetration depth/flexural toughness energy/impact energy-dust replacement level-fiber reinforcement index were also determined.
Compressive strength and modulus of elasticity of concrete are two important properties involved in the design of reinforced concrete members and sections. The main objective of this investigation was to investigate the effect of fiber aspect ratio (1/d) and fiber volume on the compressive strength and modulus of elasticity of fiber reinforced concrete (FRC), and to study the relationship between compressive strength and modulus of elasticity of FRC. in this investigation, 19 fiber reinforced concrete mixes were produced by adding three different hooked-end steel fibers of aspect ratio of 60, 75, and 83 and also six different volumes of fibers namely 0.5, 1.0, 1.25, 1.5, 1.75, and 2.0 % by volume of concrete were added for each aspect ratio. As a result, good relationships between compressive strength of FRC and the fiber reinforcement index (FRI = Vr .1/d) between modulus of elasticity and FRI, and between compressive strength and modulus of elasticity of FRC were obtained.
This paper presents the results of an investigation on the effect of Portland cement replaced by fly ash or granulated blast-furnace slag on the concrete strength at different curing temperatures. Compressive strength results are analysed according to the hyperbolic strength-age function by introducing a power indexn. The regression analysis is done considering different n values andt o (final setting times) values.
