Degree of hydration of OPC and OPC/FA pastes dried in different relative humidity

In this research; the degree of hydration of the pastes and the compressive strength of the 50 mm cubes prepared with the 100% cement and fly ash blended cement was determined. 24 hours after casting mortar cubes and the paste samples were cured for 28 days in the fog room. After 28 days curing; a set of 3 cubes and a paste sample was dried in the 100%, 75%, 65%, 40% and 12% ambient relative humidity at the constant temperature of 27oC. Drying conditions showed significant effects on the compressive strength and the degree of hydration. Highest compressive strength of 70 MPa was measured for mortar cubes dried in 100% RH; similarly 97% degree of hydration was determined for 100% cement samples dried in the 100% RH. For mortar cubes dried in 12% RH, the compressive strength was measured between 47 and 53 MPa. The similar paste samples showed the maximum degree of hydration as 81%

MAT-736: DEVELOPMENT OF HIGH STRENGTH NANO-SILICA MODIFIED RUBBERCRETE

Several research works have been carried out to study properties of concrete containing crumb rubber (rubbercrete) as a partial replacement to fine aggregate. Rubbercrete exhibits numerous benefits compared to conventional concrete such as lower in density, increased ductility, enhanced plastic capacity, higher toughness, higher impact resistance, better chloride penetration, lower thermal conductivity, higher noise reduction factor and better electrical resistivity. It has also been known to have better energy dissipation, durability and damping ratio. However, the main drawbacks of rubbercrete are decreasing in strengths and Young\u27s modulus. Therefore, to improve strengths of the rubbercrete, the crumb rubber has been pre-coated with nano-silica. Results have revealed that nano-silica modified rubbercrete can be produced with high strengths due to the densification of the interfacial transition zone (ITZ) and refining pore system of the rubbercrete

Vectors of Defects in Reinforced Concrete Structures in Onshore Oil and Gas Process Plants

There is a global outcry over the speedy deterioration of structures in oil and gas facilities. While marine environment is considered the leading factor in the deterioration of offshore structures, there is no single factor considered as the main cause of the problem in onshore structures. Therefore, the aim of this paper is to present the result of global survey on the major factors causing the deterioration of concrete structures in onshore oil and gas facilities. To realize the objectives of the paper, an e-questionnaire was administered through two International LinkedIn groups with a membership mainly dominated by experts in onshore oil and gas facilities. 159 respondents completed the questionnaires, and the reliability of the responses was calculated to be 0.950 which is considered excellent. Relative importance index was used in ranking the factors, and it was observed that environmental factors ranked as the dominant factors causing the deterioration of concrete structures in onshore process plants. Another important finding in the study is the role that experience plays on the perception of experts on the causes of defects on concrete structures

EFFECT OF SODIUM HYDROXIDE CONCENTRATION ON FRESH PROPERTIES AND COMPRESSIVE STRENGTH OF SELF-COMPACTING GEOPOLYMER CONCRETE

This paper reports the results of the laboratory tests conducted to investigate the effect of sodium hydroxide concentration on the fresh properties and compressive strength of self-compacting geopolymer concrete (SCGC). The experiments were conducted by varying the concentration of sodium hydroxide from 8 M to 14 M. Test methods such as Slump flow, V-Funnel, L-box and J-Ring were used to assess the workability characteristics of SCGC. The test specimens were cured at 70°C for a period of 48 hours and then kept in room temperature until the day of testing. Compressive strength test was carried out at the ages of 1, 3, 7 and 28 days. Test results indicate that concentration variation of sodium hydroxide had least effect on the fresh properties of SCGC. With the increase in sodium hydroxide concentration, the workability of fresh concrete was slightly reduced; however, the corresponding compressive strength was increased. Concrete samples with sodium hydroxide concentration of 12 M produced maximum compressive strength

Geopolymer concrete: effect of husk ash to compression and its microstructure properties

This research focuses on determination of cement-free geopolymer concrete capacity as an alternative to Ordinary Portland Cement concrete (OPC) for in-situ casting and the effect of utilizing waste material in polymeric concrete. pulverized fuel ash (PFA) is used as the main constituent and MIRHA as replacement by 0%, 3%, 5% and 7%. Sodium hydroxide and sodium silicate solution are used as alkali activators of silica (Si) and aluminium (Al) in main binders while sugar is added to delay the setting time of the polymeric concrete. The polymeric concrete samples are exposed to three different curing regimes namely hot gunny sack curing, ambient temperature curing and external exposure curing. Compressive strength test is carried out in 3, 7, 28 and 56 days to identify the strength of the polymeric concrete. Scanning Electron Microscopy (SEM) analysis is done to ascertain the microstructure properties of the produced polymeric concrete

SERVICEABILITY BEHAVIOR OF NORMAL AND HIGH-STRENGTH REINFORCED CONCRETE T-BEAMS

Serviceability behavior of Normal Strength Concrete (NSC) and High Strength Concrete (HSC) T-beams was experimentally evaluated. The crack pattern was observed, the effect of flange dimensions (breadth and thickness) on the crack pattern and load-deflection response was evaluated experimentally for 10 beams comprising the two studied groups, NSC and HSC T-beams. The short-term deflections were measured experimentally and predicted empirically under mid-span concentrated loading. It was found that increasing the flange width and thickness resulted in higher loads and lower deflections under service loads to a different extent. Prior to failure, the increment in the maximum loads was up to 22% while the deflection reduced by 31% for NSC and 23% for HSC beams. The available equations for determining the effective moment of inertia (Ie) were reviewed and used in predicting the Ie of the cracked beam. The results were compared with the experimental values (Iexp). The Ie showed a noticeable difference, especially for the HSC T-beams. New equations were proposed in which the tensile reinforcement ratio was considered. Compared with the other available equations, the proposed equations demonstrated a better agreement and repeatability of predicting experimental results studied herein. In addition, the proposed equations were used to predict the Ie for experimentally tested T-beams available in the literature. The proposed models showed a high degree of accuracy

Impact of construction waste minimization at construction site: case study

Waste reduction in the construction sector is essential not just from the position of overall performance, but also interests escalated recently about the detrimental impact of the waste of construction materials on the natural surroundings. The reuse and recycling of construction elements used to be substantial due to material scarcity during the war and post-war era, specifically when the price of virgin materials keep inflating. Nevertheless, the motivation to reuse and recycle construction materials has fallen ever since the flow of raw materials has grown more consistent and satisfactorily. This paper involves an ongoing sequence of waste audits at Universiti Teknologi Petronas (UTP) R&D construction sites. The methodology consists of discussion, observation and quantitative evaluations of the kinds and distribution of wastes. The finding of this study demonstrates that the project aimed at both minimizing the volume of waste generated and diverting as much waste as possible from landfill that contribute to the recycle with over 1200 tonnes of material which constitute about 73% of recycle and reused rate mainly from timber and metal

Effectiveness of used engine oil on improvement of properties of fresh and hardened concrete

Use of mineral admixtures, processed and unprocessed industrial by-products and domestic and agricultural wastes as raw materials in cement and concrete is becoming popular. This has a positive environmental effect as the cost of safe disposal of waste is significantly higher and there are strict environmental regulations. Some references indicate that the leakage of oil into the cement in older grinding units resulted in concrete with greater resistance to freezing and thawing. This effect is similar to adding an air-entraining chemical admixture to the concrete. However, the hypothesis is not backed by significant research study reported in the available literature. This research study was conducted to investigate the effects of used engine oil on properties of fresh and hardened concrete. The main variables included the type and dosage of an airentraining agent (SIKA AER commercially available air entraining agent, used engine oil, and new engine oil). Results showed that used engine oil increased the slump between 18 to 38% and air content between 26 to 58% with respect to the control mix containing no admixture, used engine oil reasonably reduced the porosity and did not adversely affect the strength properties of hardened concrete

Properties of concrete containing used engine oil

Since last few years cement replacement materials, industrial by-products and agricultural wastes in concrete production are widely used. It imparts positive environmental effect because the waste materials are not released to the environment. It was reported that the leakage of motor oil onto concrete surfaces in old grinding units increased the resistance such concrete to freezing and thawing, it made to understand that the effect is similar to adding an air-entraining chemical admixture to the concrete. However, the hypothesis is not backed by significant research study and not reported in the available literature. This paper presents results of the experimental study conducted to investigate the effects of used engine oil on properties of fresh and hardened concrete.  With the addition of used engine oil, concrete slump was increased by 18% to 38% and air content by 26% to 58% as compare to the slump of control concrete. Porosity and oxygen permeability of concrete containing used engine oil was also reduced and the compressive strength was obtained approximately same as that of the control mi

Performance Comparison between EAFD and Conventional Supplementary Cementing Materials

Sustainability of concrete construction necessitates exploring potential renewable resource, especially from industrial waste products.  Electric arc furnace dust (EAFD), a by-product of the modern electric arc furnace (EAF) process from the steel manufacturing industry has an adverse impact on the environment. Utilizing EAFD in concrete production as a cement replacement material together with silica fume (SF) and fly ash (FA) has raised the interest of many researchers.  This study investigates the use optimum 5% EAFD content refers to both 15% SF and 20% FA in water binder ratio of 0.5 and sand to cement ratio of 2. The aim of this study is to obtain the percentage replacement levels of EAFD that are equivalent to the SF and FA regarding workability, setting time, compressive strength and resistance to rapid chloride permeability. The compressive strength results showed that replacement of 5% SF and 15% FA are the equivalent replacement levels to 3% EAFD. Similarly, results from resistance to rapid chloride permeability showed that the optimum EAFD content performed better than the replacement levels of FA.  However, SF replacement levels showed the best resistance to rapid chloride permeability. Therefore, 3% replacement of EAFD provided an intermediate performance between the optimum SF and FA contents and exceeded that of the control