Construction cost estimating is completed only when all details of the activity are scrutinized. This involves looking at all work cycles and all associated motion analyses. It becomes important to count all the minutes and seconds to arrive at the total hours of a work package. When work cycles feed into or take over from dependent work cycles, then it is important to calculate and adjust the appropriate number of resources – workers and equipment – required to accomplish the work without delaying subsequent work cycles. This article outlines the details of multiple work cycle analyses and calculates the cost of labor involved by presenting appropriate rationale based on a labor-intensive construction method and work approach. This article studies a traditional concrete pour using a concrete mixer, hoist, and workers and provides a how-to-do-it technique. The labor-intensive construction method studied is still used in many parts of the world.
The use of self-compacting concrete (SCC) is gaining significance for reasons of its high flowability without segregation. However, the flowability performance of SCC as indicated by the standard tests is different from that observed in field particularly in the congested reinforcement areas of structural elements. The congested reinforcement poses multiple lines of resistance to the flow of SCC. This paper presents an experimental investigation on the flow performance of SCC against multiple resistance from the reinforcement. For simulating the multiple lines of resistance to the flow of SCC, a new test named as ‘constrained flow test (CFT) of SCC’ has been attempted. The parameters of the investigation include the diameter and spacing of reinforcement. The results indicated that the variation of the diameter of reinforcement relative to its spacing has a significant influence on the flowability of SCC. A new parameter termed as ‘flowability coefficient’ which takes in to account the effect of spacing and diameter of reinforcement on the slump flow of SCC has been proposed and quantified.
An enormous amount of coal combustion ash is generated by Indian power industries. The storage of coal bottom ash on land pollutes the environment and endangers living beings. This study aimed to assess the viability of utilizing coal bottom ash as a fine aggregate in concrete. The use of coal bottom ash in the production of concrete will provide a cost-effective and environmentally sustainable technique of industrial waste disposal and natural sand conservation. The mechanical qualities as well as thermal performances in tropical climatic conditions of concrete with CBA (coal bottom ash) with up to 40 % replacement of sand were promising. The durability of concrete that incorporates CBA as a sand replacement is just as significant as the mechanical qualities. In this work, a guarded hot box and thermal conductivity test apparatus are used to assess the overall thermal transmittance (U value) and thermal conductivity, respectively in Indian climatic conditions. Typically used roof samples of 500*500*100 mm dimensions with different percentages of bottom ash have been tested. The results showed a correlation between the percentage increase in bottom ash substitution for sand and a subsequent reduction in the U value.
Prestressed strands in concrete can experience corrosioninduced degradation in the presence of chlorides, which involves degradation of both surface and bulk metal - leading to brittle failure. Detection of such degradation at an early stage is critical and is difficult with the conventional approaches. This paper presents an approach to locate corroding sites in pretensioned concrete (PTC) structures at an early stage, based on electrochemical and microstructural characterization. Test specimens were naturally passivated and subsequently exposed to chlorides. The evolution of electrochemical impedance spectroscopy (EIS) responses obtained from prestressed steel embedded in (a) ordinary Portland cement (OPC), and (ii) OPC with 30 % Class F fly Ash (5 specimens each) during passive-toactive transition is discussed. The magnitudes of measured EIS parameters corresponding to the passive and active stages were found to be clearly distinguishable. A significant difference in the pattern of the associated EIS responses was also observed. The correlation between the condition of the passivated steel surface and low-frequency EIS (Bode) responses is finally presented with the suggestion to utilize qualitative EIS analysis for the identification of corroding locations in a PTC structure.
The concept of modular ratio in reinforced concrete is used in the working stress method to transform the composite section into an equivalent concrete section. Different formulae are provided in different codes for the modular ratio and Ec. The formulae given in IS: 456 (2000), Draft IS: 456, Eurocode 2, ACI 318-19, and IS: 11384 (2022) codes are compared. Among the different code formulae, only the IS: 456 code gives a different expression for the modular ratio, and it is believed that this expression is based on long-term experiments and partially takes into account long term effects such as creep. As per other codes, the modular ratio is dependent of Ec. The expression for Ec given in the IS: 456 code gives higher values than that of the ACI code expression. In addition, both the codes state that the measured values of Ec may differ by ± 20 % from the values obtained from the expression given in the codes. An equation, originally suggested by Noguchi, et al., 2009, which is applicable to a wide range of aggregates and mineral admixtures used in concrete and is valid for high-strength concrete also may be used to get more accurate value of Ec. In addition, many codes state that the effects of creep can be considered by taking into account the creep coefficient, whose value may range between 1 and 3. Even if the creep coefficient is taken as 1.0, the value of the modular ratio increases by 100 %. A higher m value generally leads to less deflection
December 2024
Volume - 98
Number : 12
November 2024
Volume - 98
Number : 11
October 2024
Volume - 98
Number : 10
September 2024
Volume - 98
Number : 09
August 2024
Volume - 98
Number : 08
July 2024
Volume - 98
Number : 07
June 2024
Volume - 98
Number : 06
May 2024
Volume - 98
Number : 05
April 2024
Volume - 98
Number : 04
March 2024
Volume - 98
Number : 03
February 2024
Volume - 98
Number : 02
