Influence of local rice husks ash on compressive strength of normal-strength concrete

Strength Concrete ◽

Normal Strength ◽

Recycled Waste ◽

Medical Glass

The possibility of using recycled waste medical-glass aggregate (RGA) as a fine aggregate in the production of normal-strength concrete was investigated in this study. The influence of RGA as crushed sand (CS) replacement at different levels (by volume) of 0 – 100% (an interval of 20%) on the engineering properties and durability of concrete was also studied. Results show that the replacement of CS by RGA insignificantly affected the workability and unit weight of fresh concrete mixtures. Besides, using RGA to replace 20 – 60% CS was beneficial in terms of compressive strength, drying shrinkage, and ultrasonic pulse velocity (UPV). At these replacement levels, the dry density values were found to increase and the water absorption values were reduced as well. However, replacing CS with RGA up to 80% and 100% caused a reduction in compressive strength, dry density, and UPV and an increase in water absorption and drying shrinkage of concretes. Closed correlations among the above-mentioned concrete properties were also found in this study. All of the concrete samples obtained compressive strength values higher than the target strength (≥ 25 MPa) and they were classified as very good quality concretes with UPV values of above 4100 m/s. The experimental results demonstrate a high possibility of producing normal-strength concrete with a fine aggregate of RGA as either partially or fully replacement of CS. This also provides an environmentally-friendly solution for recycling waste medical glass in construction materials for sustainable development.

Superplasticizer for High Strength Concrete

MRS Proceedings ◽

10.1557/opl.2015.324 ◽

2015 ◽

Vol 1768 ◽

Author(s):

Luis E. Rendon Diaz Miron ◽

Maria E. Lara Magaña

Keyword(s):

Compressive Strength ◽

Portland Cement ◽

High Strength Concrete ◽

High Strength ◽

Mineral Admixtures ◽

Strength Concrete ◽

Normal Strength ◽

Ready Mixed Concrete ◽

Mixed Concrete

ABSTRACTIn the early 1970s, experts predicted that the practical limit of ready-mixed concrete would be unlikely to exceed a compressive strength greater than 90 MPa [1]. Over the past two decades, the development of high-strength concrete has enabled builders to easily meet and surpass this estimate. The primary difference between high-strength concrete and normal-strength concrete relates to the compressive strength that refers to the maximum resistance of a concrete sample to applied pressure. Although there is no precise point of separation between high-strength concrete and normal-strength concrete, the American Concrete Institute defines high-strength concrete as concrete with a compressive strength greater than 45 MPa. Manufacture of high-strength concrete involves making optimal use of the basic ingredients that constitute normal-strength concrete. When selecting aggregates to obtain high-strength concrete, we consider strength, optimum size distribution, surface characteristics and a good bonding with the cement paste that affect compressive strength. Selecting a high-quality Portland cement and optimizing the combination of materials by varying the proportions of cement, water, aggregates, and admixtures is also necessary. Any of these properties could limit the ultimate strength of high-strength concrete. Pozzolans, such as fly ash and silica fume along with silicic acid, are the most commonly used mineral admixtures in high-strength concrete. These materials impart additional strength to the concrete by reacting with Portland cement hydration products to create additional Calcium Silicate Hydrate (CSH) gel, the part of the paste responsible for concrete strength; finally the most important admixture is polycarboxylate ether as super plasticizer. It would be difficult to produce high-strength ready-mixed concrete without using chemical admixtures. In this paper we study the use of high performance concrete (HPC) to obtain very narrow strong pre-fabricated elements for water conducting channels.

In Situ Inspection of Ultra Durable Concrete Using Electrical Resistivity Technique

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.368-373.1989 ◽

2011 ◽

Vol 368-373 ◽

pp. 1989-1992

Author(s):

Tze Yang Darren Lim ◽

Bahador Sabet Divsholi ◽

Susanto Teng

Keyword(s):

Compressive Strength ◽

Electrical Resistivity ◽

Strength Concrete ◽

Chloride Diffusivity ◽

Concrete Quality ◽

Concrete Resistivity ◽

In today’s rapid construction, a reliable method for quick evaluation of concrete quality during construction is very important. The compressive strength of concrete has been used to evaluate the mechanical properties of concrete; however compressive strength may not represent the durability of concrete. Rapid Chloride Migration Test (RCMT) and electrical resistivity can be used to evaluate the durability of concrete. Obtaining the coefficient of chloride diffusivity from RCMT usually requires a testing duration of 24 hours or less for normal strength concrete. With the inclusion of supplementary cementitious materials and lower water/cementitious ratio to achieve a higher strength and more durable concrete, testing of the concrete becomes an elaborate affair which might takes at least four to five days of testing. Electrical resistivity technique has been used to evaluate the quality of normal strength concrete. However the suggested classification of concrete quality is not applicable to ultra durable concrete. In this work, the effectiveness of using the concrete resistivity test results from electrical resistivity technique is studied. With the use of direct and four points Wenner probe methods, the concrete resistivity results were obtained and compared with the coefficient of chloride diffusivity from RCMT. Six mixes of three different grades with the inclusion of 30% granulated ground blast-furnace slag and 10% undensified silica fume were designed and tested; and high correlation coefficients (>0.94) for all the mixes were achieved. This represents the effectiveness of using the electrical resistivity technique to carry out fast and accurate in-situ test to determine the quality of the ultra durable concrete.

Effect of Maximum Aggregate Size on the Strength of Normal and High Strength Concrete

Civil Engineering Journal ◽

10.28991/cej-2020-03091537 ◽

2020 ◽

Vol 6 (6) ◽

pp. 1155-1165

Author(s):

Gaith Abdulhamza Mohammed ◽

Samer Abdul Amir Al-Mashhadi

Keyword(s):

Compressive Strength ◽

High Strength Concrete ◽

Coarse Aggregate ◽

Design Method ◽

High Strength ◽

Maximum Size ◽

Normal Concrete ◽

Strength Concrete ◽

Aggregates form 60% to 75% of concrete volume and thus influence its mechanical properties. The strength of (normal or high-strength) concrete is affected by the maximum size of a well-graded coarse aggregate. Concrete mixes containing larger coarse aggregate particles need less mixing water than those containing smaller coarse aggregates, In other words, small aggregate particles have more surface area than a large aggregate particle. In this research, about twenty-two mixtures were covered to study the effect of the MSCA, on compressive strength of (normal strength concrete) and Sixteen mixtures to study the effect of the maximum size of coarse aggregate on compressive strength for (high strength concrete). The concrete mixture is completely redesigned according to the maximum size of coarse aggregate needs and maintaining uniform workability for all sizes of coarse aggregate. The American design method was adopted ACI 211.1, for normal concrete. ACI 211-4R, the design method was adopted for high strength concrete. And use the MSCA with dimensions (9.5, 12.5, 19, 25, 37.5, and 50) mm for normal strength concrete and the MSCA (9.5, 12.5, 19, and 25) mm for high strength concrete. The slump was fixed (75-100) mm for normal strength concrete. Slump is fixed to (25-50) mm for high strength concrete before added Superplasticizer high range water reducer (HRWR). With Fineness Modulus (F.M) fixed to 2.8 for both normal concrete and high-strength concrete. According to the results of the tests, the compressive strength increases with the increase in the MSCA, of the normal concrete and also high – strength concrete. And the effect of the MSCA, on the compressive strength of normal concrete, is higher than that of high-strength concrete.

Residual properties of normal-strength concrete subjected to fire and sustained elevated temperatures: A comparative study

Journal of Structural Fire Engineering ◽

10.1108/jsfe-02-2020-0007 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Sachin V. ◽

N. Suresh

Keyword(s):

Compressive Strength ◽

Electric Furnace ◽

Elevated Temperatures ◽

Surface Hardness ◽

Maximum Temperature ◽

Content Type ◽

Strength Concrete ◽

Residual Properties ◽

Purpose Concrete is a widely used construction material which can be prepared using locally available resources (aggregates, cement and water) by following relevant standard guidelines. The residual properties of concrete determined by heating in an electric furnace may not produce a similar effect of fire. The purpose of this paper is to compare the effect of a fire with that coming from the exposure of normal strength concrete to predetermined reference temperatures, for which two sets of specimens were heated in a fire furnace provided with gas burners and an electric furnace. Design/methodology/approach The concrete cubes and cylinders were subjected to 200oC, 400oC, 600oC and 800oC temperature in a gas-controlled fire furnace and an electric furnace for 2 h. The physical properties and mechanical properties of concrete were determined after cooling the specimens in air. The quality of concrete specimens was determined using the ultrasonic pulse velocity test, and surface hardness of the heat-exposed cubes was recorded using the Schmidt rebound hammer. Findings The fire-exposed specimens were found to have lower residual compressive strength, tensile strength and higher porosity/voids/internal cracks than the specimens heated in an electric furnace at the same temperature. Further, a good agreement with compressive strength and rebound numbers was observed for each of the two heating systems (flames coming from gas burners and electric furnace). Originality/value Normal strength concrete specimens exposed to heat in an electric furnace will not give the same effect of fire having the same maximum temperature. Further, it is noticed that concrete subjected to elevated temperature is sensitive to heating modalities, be it the flames of a gas furnace or the radiation of an electric furnace.

Mechanical and Microstructure Characterization of Fresh High- and Normal- Strength Concrete with Non-Contact Electrical Resistivity Measurement

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.250-253.122 ◽

2011 ◽

Vol 250-253 ◽

pp. 122-130

Author(s):

Ye Tian ◽

Xian Yu Jin ◽

Yuan Zhan ◽

Nan Guo Jin

Keyword(s):

Compressive Strength ◽

Electrical Resistivity ◽

Resistivity Measurement ◽

Electrical Resistivity Measurement ◽

Design Quality ◽

Bulk Resistivity ◽

Archie’S Law ◽

Strength Concrete ◽

This paper reports the investigation on both high and normal strength concrete using a non-contact electrical resistivity facility. The bulk resistivity development (ρ(t)-t curves) of the fresh concretes was evaluated from casting to 72h. The relationship between the electrical resistivity and the pore structure obtained from mercury intrusion porosimetry (MIP) method was analyzed. And the compressive strength evolution of fresh high- and normal- strength concrete was studied based on the bulk resistivity at early ages. The experiment results indicated a linear relationship between the fractional porosity and electrical resistivity. A further correlation between the compressive strength and electrical resistivity was analyzed with Archie’s law. Based on these studies, it appears that the electrical resistivity test could provide information for the design, quality control, quality assurance, and utilization of both high- and normal- strength concrete.