Masonry Magazine June 1989 Page. 9
Research Investigation of MASON PRODUCTIVITY
NCMA Research & Development Laboratory
Sponsored by National Concrete Masonry Association Expanded Shale, Clay & Slate Institute
Designed by Masonry Consultants, DeBary, Florida
Preface
This research program was carried out under the supervision of Mr. Reg Miller, Masonry Consultants, and Mr. Ed Hedstrom, Director of Research and Development, National Concrete Masonry Association.
Construction of the test walls was conducted in a controlled environment to prevent the introduction of outside variables which might directly or indirectly influence the results of the study.
The National Concrete Masonry Association, the Expanded Shale, Clay And Slate Institute, and Masonry Consultants make no claims, expressed or implied, as to the relevance of production rates determined as a result of this limited investigation to actual production rates which may be expected under actual job site conditions.
Results of this study shall not be used for estimating purposes and may not be reproduced without written approval of the sponsoring organizations.
Abstract
This report presents the results of research conducted on concrete masonry to determine the effect of such properties as unit size and weight on mason productivity.
The investigation was carried out in a controlled environment to avoid the introduction of additional variables which might influence the results and/or render it impossible to duplicate the test conditions at some later date and location.
Four concrete masonry walls were constructed under close supervision using 16" and 24" long lightweight and heavyweight units. The original intent was for all four walls to be constructed of the same width. However, due to the inability to locate a source of 6"x8"x24" heavyweight units, it was decided to construct the two walls consisting of 24" long units of a different width and bonding pattern of that selected for the 16" units.
It therefore was possible to make a direct comparison of the productivity rates of only two courses of the walls constructed of 16" and 24" long units.
However, direct comparison between the courses of walls constructed of 16" long lightweight and heavyweight units and the courses of walls constructed of 24" long lightweight and heavyweight units was possible.
By summing the measured times of all the courses of each wall it can be shown that the production rate of the wall constructed of 16" long lightweight units exceeds that of the wall constructed of 16 heavyweight units by approximately 14.7%. In like manner it can be shown that the production rate of the wall constructed of 24" long lightweight units exceeds that of the wall constructed of 24" heavyweight units by approximately 18.7%.
Generally speaking, productivity increased as the weight of the units decreased and the length of the units increased.
Printed with permission of the National Concrete Masonry Association, Herndon, VA.
1.0 Research Objective
The objective of this investigation was to document the effect of concrete masonry physical properties, weight and size, on the comparative times required for a mason to place the units in a wall of predetermined length and height.
The objective also included documenting the relationship between the time required to lay units of varying size and weight at different courses (heights) within the wall, and the relationship between the time required to lay units facing the line (line along the inside face of the wall) and the time required to lay the units overhand (line along the outside face of the wall).
The investigation was designed in such a manner to insure its reproducibility at other locations across the country to establish the validity of the results obtained.
The tests results are intended to be used as a guide to develop recommendations for the implementation of materials and/or methods designed to decrease time and costs required for the construction of concrete masonry walls.
2.0 Scope
This test program involved the construction of four concrete masonry walls using concrete masonry units of different size and weight, but consisting of the same number of courses and being equal in size in total area of exposed wall surface.
Variables included size of units (width and length), weight of units, and method of placement (laid facing the line or overhand). Measurements were taken of the time required to complete the individual courses and recorded.
Although fatigue is an important consideration in any task involving manual lifting and repetitive movements, no provisions for the introduction of a fatigue factor was provided.
Economic considerations, such as those related to material costs, additional labor to place units above 4'-0", etc., are beyond the scope of this investigation.
3.0 Material Properties
# 3.1 Concrete Masonry Units
Concrete masonry units for use in this investigation were selected on the basis of two variables: unit weight (density) and length.
Unit Weight:
Lightweight units were to be manufactured from concrete having a unit weight of 85 lbs. per cu. ft.
Heavyweight units were to be manufactured from concrete having a unit weight of 135 lbs. per cu. ft.
However, unit weights of the concrete from which the units actually used during the course of this investigation were found to vary from 84.1 to 101.6 pcf for lightweight units and 126.6 to 133.8 for heavyweight units.
Length:
Two sizes of concrete units were employed: those having a nominal length of 16 inches (15% actual) and those having a nominal length of 24 inches (23% actual).
A complete description of the concrete masonry units used is as follows: