97 publications from this institution
Abstract Using Test Method for Time of Setting of Concrete Mixtures Paste by Penetration Resistance (ASTM C 403), Proctor penetration resistance was determined under isothermal curing temperatures ranging from 6 to 80°C for concretes containing up to 50% of fly ash or ground-granulated blast-furnace slag. The results show that as the temperature increases, the initial and final setting times decrease for all types of concrete, with fly-ash concrete having the longest setting times. At high temperatures, slag concrete has shorter setting times than Type I cement concrete. Relationships are presented for setting time as a function of penetration resistance, temperature, and cement replacement level.
This study provides the experimental and statistical modeling in order to increase the performance of ultra high performance concrete (UHPC) within reducing the cement consumption. Also showing the effect of waste glass powder and nano silica fume on mechanical, rheological, and shrinkage properties. For this purpose, a fraction of binder was added with the range of 0–5% of nano-silica fume and fraction of Portland cement were substituted with 0–20% of waste glass powder, the maximum particle size of 63 μm. The mechanical properties were obtained by testing on 28 days compressive strength. The rheological property found by doing the flow test. Numbers and randomization orders of experiments were designed by central composite face-centered (CFC) and modeled by response surface methodology (RSM). The validity of models was controlled by analysis of variance (ANOVA). The study showed adding nano-silica and waste glass powder and especially their interaction improved the properties of UHPC.
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.
Abstract Discarding of old rubber tires is indeed a very serious environmental problem all over the world represented by a high risk for uncontrolled fires and other environmental and health hazards. It was estimated that every year about one billion tires get to the end of their life span. Recently, the construction industry has taken up the challenge to incorporate recycled materials in concrete mixtures by means aggregate replacement. Nowadays, many researches are focused on investigating rubberized concrete as a structural material due to its enhanced properties such as ductility, energy dissipation and damping ratio. Previous studies have suggested the use of fine rubber particles rather than coarse ones when high strength concrete is targeted despite the fact that using coarse ones provide enhanced energy dissipation, damping ratio and vibration behavior. This study is intended to address the effects of utilizing significant amount of well graded fine and coarse rubber aggregates on the properties of high strength concrete. On the basis of the investigations some mechanical, durability and dynamic tests will be conducted on concrete with different rubber replacement percentages. The results of the experimental works have shown that it is possible to develop high strength concrete when well graded fine and coarse rubber particles is used to replace 25% percent of the natural aggregates. Furthermore, the vibration behavior of the concrete mixture was improved considerably when high content of rubber aggregates was added into concrete.
Sulfur concrete represents a promising sustainable alternative to traditional Portland cement due to its rapid setting time, superior chemical resistance, and recyclability. Nonetheless, inherent brittleness and susceptibility to long-term deterioration limit broader applications, necessitating effective modifiers to improve mechanical and durability performance. This study investigates the influence of incorporating high density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) at dosages of 5, 10, 15, and 20 wt.% into sulfur concrete containing 30 wt.% sulfur. Comprehensive evaluations included mechanical testing (compressive, flexural, and tensile strength), non-destructive testing methods (ultrasonic pulse velocity and rebound hammer), accelerated corrosion assessments via impressed voltage technique, and microstructural analyses (SEM, FTIR, and XRD). Results revealed optimum mechanical performance at 5 wt.% polymer content, with LLDPE modification achieving maximum compressive, flexural, and tensile strengths of 25.24 MPa, 3.31 MPa, and 1.75 MPa, respectively, compared to the control’s 20.6 MPa, 2.75 MPa, and 1.21 MPa. Corrosion resistance significantly improved with polymer additions, notably at 20 wt.% LLDPE exhibiting the lowest current intensity (~0.03 A). SEM analysis confirmed enhanced matrix density with HDPE modification, whereas FTIR and XRD analyses indicated no chemical interactions, affirming physical blending. These findings highlight that carefully selected polymer modifications significantly enhance the mechanical integrity and durability of sulfur concrete for sustainable infrastructure applications.
Abstract There are many test methods to measure the impact resistance of fiber-reinforced concrete that are complicated, time consuming, and expensive. A practical test method has been developed to measure the impact resistance of high-strength fiber-reinforced concrete (HSFRC). The equipment developed can also be used for testing aggregate impact values by simply changing the base plate of the machine. A machine was developed to measure the surface abrasion resistance of HSFRC. Testing fiber-reinforced concrete for surface abrasion resistance was found to be extremely difficult if realistic and practical results were desired. In this study the influence of silica fume on the properties of HSFRC was investigated by using silica fume at two different percentages and with 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 percentages of 0.5, 1.0, and 2.0% by volume of concrete. The results show that including fibers in high-strength concrete improves impact resistance, surface abrasion, and splitting tensile strength.
Usually, a material of higher strength does not necessarily indicate in a higher structural performance. While a higher energy absorbing material usually expresses higher structural performance when failure happens. This study aims at finding the relation between 28-days compressive strength and Compression toughness factor of Ultra High Performance Concrete (UHPC) using varying range of five variables which include; Steel Fiber, Silica fume (SF), Cement 42.5, Superplasticizer (SP), and water to cemetiotious ratio (w/c) by Design of Experiments (DOE) methodology. The results shows the significant relationship between the Compression toughness factor and 28 days compressive strength of UHPC. The model is valid for the mixes made with 1.0 sand, 0.15-0.30 silica fume amount, 0.70-1.30 cement amount, 0.10- 0.20 steel fiber, 0.04- 0.08 superplasticizer (all values are by aggregate weight mass) and 0.18- 0.32 water to cementitious ratio.
One of the effective vibration control systems used for structures is the semi active tuned mass damper (STMD), which is popular since it is reliable and simple. STMD characteristics in the design for piled foundations are usually obtained by modelling the foundation raft only to incorporate the soil structure interaction (SSI). However, as it proposed in the recent studies the role of SSI and simulation of piled raft in the analyses proved to be very important in the determination of the STMD parameters. Hence, in this study, efficiency of STMD with respect to the control of seismic response of the structure, is studied by considering the soil-pile-structure interaction (SPSI). Nonlinear time history analysis is applied for a three-layered soil profile including pile foundations by using the well-known substructure (spring) model under two different ground motion records. In order to increase the accuracy of the results, soil profile with piles and building structure with STMD are considered all at once in a single model under the action of seismic loading, named as direct method. P-Y curves which are suggested by American Petroleum Institute (API) are used in the spring method for simulating soil-pile-structure interaction. The results showed that, adjusting the STMD characterizations on piled structures without considering the soil-pile-structure interaction may result to ineffective control of the seismic vibration and in the worst case may lead to amplification of the vibration of buildings.
An experimental investigation was carried out to evaluate the seismic behaviour of 200 × 200 mm2 reinforced-concrete columns with an embedded drain pipe subjected to monotonic and reversed cyclic loading. Nine full-scale specimens were prepared, including two control specimens without an embedded pipe and seven specimens with a pipe embedded in the column core. Among the latter seven columns, two were highly confined using 8 mm dia. ties with 80 mm spacing, while a 200 mm spacing was used in the other columns. The test results indicated that the pipe adversely affected the column's load-carrying capacity, load–displacement response and ductility. The extent of the adverse effect was found to depend on the level of axial load, the degree of confinement and the distance of the pipe exit from the column base. Due to local stress concentration, some local damage was observed in the vicinity of the pipe exit, but the provision of high confinement in the pipe exit region significantly improved the overall behaviour of the column under reversed cyclic loading.
No abstract is provided for this article.
This paper aims to model the effects of five different variables which includes: cement content (C), the steel fiber amount (F), the silica fume amount (SF), the superplasticizer (SP), the silica fume amount (SF), and the water to cementitious ratio (w/c) on 28 days flexural toughness of Ultra High Performance Concrete (UHPC) as well as, a study on the variable interactions and correlations by using analyze of variance (ANOVA) and response surface methodology (RSM). The variables were compared by fine aggregate mass. The model will be valid for the mixes with 0.18 to 0.32 w/c ratio, 4 to 8 percent steel fiber, 7 to 13 percent cement, 15 to 30 percent silica fume, and 4 to 8 percent superplasticizer by fine aggregate mass.
