Title:
Point Load Test for Estimation of Concrete Compressive Strength
Author(s):
David N. Richardson
Publication:
Materials Journal
Volume:
86
Issue:
4
Appears on pages(s):
409-416
Keywords:
compressive strength; concretes; loads (forces); mechanical tests; tensile strength; tests; Materials Research
DOI:
10.14359/2189
Date:
7/1/1989
Abstract:
The point-load index is presented as a convenient alternate method for determination of relative strength of concrete or as a method of estimation of concrete compressive strength. The test method is presently accepted in the rock mechanics field but is relatively new to the concrete area. The test is quick, inexpensive, reproducible, and the equipment is portable. The test involves the application of a load via two conical platens across the diametral or axial axis of cores or cylinders. In this study, several test variables were evaluated, including three specimen diameters (50.8, 76.2, and 101.6 mm [2, 3, and 4 in.]) two types of coarse aggregate (river gravel and crushed limestone), two types of diameter (initial and final), and two directions of loading (diametral and axial). A total of 36 mixes was evaluated for over 1000 point-load specimens. It was concluded that there is a strong relationship between point-load index and compressive strength. It is recommended that for compressive strength estimations, each job-mix relationship be individually determined. Two methods of size correction are presented. For most purposes, initial specimen diameter should be used for calculation of the point-load index, and the specimens should be loaded diametrally for testing cast cylinders and cores drilled parallel to concrete "bedding" planes.