Method and apparatus for testing compressive strength of concrete and the like

Claim 1

The method of determining the compressive strength of concrete composed of a mixture of sand, cement, and aggregate, comprising driving a large number of investigative probes into a plurality of series of set concrete samples at various times after setting to a depth below a shear failure cone, all samples of a given series using the same aggregate of a known hardness, cracking the coarse aggregate by driving the probes, using generally cylindrical probes with a penetrating nose portion having a conical tip whose included angle is between 60* and 135* and using a poWder charge to drive said probes through a gun barrel, all of said probes being of substantially uniform physical dimensions and structure, all of said powder charges being uniform in composition and weight with the explosive force of said charge uniformly applied to the driven probe, measuring the exposed length of said investigative probes, calibrating the exposed length of said investigative probes in terms of compressive strength of the concrete by associating the penetration of each of the probes with an independent measurement of the compressive strength of each of the respective samples tested by a standard testing procedure such as cutting a test core from the concrete sample adjacent the investigative probe or casting a test cylinder at the time of pouring the concrete sample tested and then crushing said test cores and cylinders using accepted procedures and recording the compressive strength of each concrete sample so determined with the exposed length of the associated investigative probe, the record for each series of samples being separated according to aggregate hardness, then driving a test probe into an unknown concrete sample in which the aggregate hardness is known to a depth below a shear failure cone, the test probe and driving conditions being held substantially exactly the same as in the case of driving said investigative probes, measuring the exposed length of said test probe, and the compressive strength of the unknown concrete sample then obtained by using the calibration of an investigative probe having the same exposed length as the test probe in the unknown sample when driven in the same manner into concrete in which the same aggregate occurs of the said known hardness.

Claim 2

The method of determining the compressive strength of concrete composed of a mixture of sand, cement, and aggregate, comprising driving a large number of investigative probes into a plurality of series of set concrete samples at various times after setting to a depth below a shear failure cone, all samples of a given series using the same aggregate of a known hardness, cracking the coarse aggregate by driving the probes, using generally cylindrical probes with a penetrating nose portion having a conical tip whose included angle is between 60* and 135* and using a poWder charge to drive said probes through a gun barrel, all of said probes being of substantially uniform physical dimensions and structure, all of said powder charges being uniform in composition and weight with the explosive force of said charge uniformly applied to the driven probe, measuring the exposed length of said investigative probes, calibrating the exposed length of said investigative probes in terms of compressive strength of the concrete by associating the penetration of each of the probes with an independent measurement of the compressive strength of each of the respective samples tested by a standard testing procedure such as cutting a test core from the concrete sample adjacent the investigative probe or casting a test cylinder at the time of pouring the concrete sample tested and then crushing said test cores and cylinders using accepted procedures and recording the compressive strength of each concrete sample so determined with the exposed length of the associated investigative probe, the record for each series of samples being separated according to aggregate hardness, then driving a test probe into an unknown concrete sample in which the aggregate hardness is known to a depth below a shear failure cone, the test probe and driving conditions being held substantially exactly the same as in the case of driving said investigative probes, measuring the exposed length of said test probe, and the compressive strength of the unknown concrete sample then obtained by using the calibration of an investigative probe having the same exposed length as the test probe in the unknown sample when driven in the same manner into concrete in which the same aggregate occurs of the said known hardness.

Claim 5

The method of determining the compressive strength of concrete composed of a mixture of sand, cement and aggregate, comprising driving a large number of investigative probes into a plurality of series of set concrete samples at various times after setting, each series having the same type of aggregate of substantially uniform hardness, performing a scratch test for hardness of various aggregate found in said samples and segregating records thereof according to aggregate hardness, cracking the coarse aggregate by driving the probes using generally cylindrical probes with a penetrating portion having a conical tip whose included angles is between 60* and 135* followed by an outwardly flaring portion preventing rebound of a driven probe, and using a powder charge to drive said probes through a gun barrel, all of said probes being of substantially uniform physical dimensions and structure, all of said powder charges being uniform in composition and weight with the explosive force of said charge uniformly applied to the driven probe, measuring the exposed length of said investigative probes, calibrating the exposed length of said investigative probes segregated in series according to aggregate hardness in terms of compressive strength of the concrete by associating the penetration of each of the probes with an independent measurement of the compressive strength of each of the respective samples tested using standard testing procedures, recording the compressive strength of each concrete sample so determined with the exposed length of the associated investigative probe segregated according to aggregate hardness, then driving a Test probe into an unknown concrete sample in which the aggregate hardness is correlated with said above mentioned scratch test hardness, the test probe and driving conditions being held substantially exactly the same as in the case of driving said investigative probes, measuring the exposed length of said test probe, and the compressive strength of the unknown concrete sample then obtained by using the previously prepared calibration of an investigative probe, having the same exposed length as the test probe in the unknown sample, when driven into concrete in which the same aggregate occurs of the said known hardness.

Claim 6

The method of determining the compressive strength of concrete composed of a mixture of sand, cement and aggregate, comprising driving a large number of investigative probes into a plurality of series of set concrete samples at various times after setting, each series having the same type of aggregate of substantially uniform hardness, performing a scratch test for hardness of various aggregate found in said samples and segregating records thereof according to aggregate hardness, cracking the coarse aggregate by driving the probes using generally cylindrical probes with a penetrating portion having a conical tip whose included angles is between 60* and 135* followed by an outwardly flaring portion preventing rebound of a driven probe, and using a powder charge to drive said probes through a gun barrel, all of said probes being of substantially uniform physical dimensions and structure, all of said powder charges being uniform in composition and weight with the explosive force of said charge uniformly applied to the driven probe, measuring the exposed length of said investigative probes, calibrating the exposed length of said investigative probes segregated in series according to aggregate hardness in terms of compressive strength of the concrete by associating the penetration of each of the probes with an independent measurement of the compressive strength of each of the respective samples tested using standard testing procedures, recording the compressive strength of each concrete sample so determined with the exposed length of the associated investigative probe segregated according to aggregate hardness, then driving a Test probe into an unknown concrete sample in which the aggregate hardness is correlated with said above mentioned scratch test hardness, the test probe and driving conditions being held substantially exactly the same as in the case of driving said investigative probes, measuring the exposed length of said test probe, and the compressive strength of the unknown concrete sample then obtained by using the previously prepared calibration of an investigative probe, having the same exposed length as the test probe in the unknown sample, when driven into concrete in which the same aggregate occurs of the said known hardness.

Claim 16

The method of performing a dependably reproducible test for the compressive strength of concrete composed of a mixture of sand, cement and an aggregate of known hardness, any time after setting with commercially acceptable accuracy, comprising driving a number of investigative probes into a plurality of series of concrete samples at various times after setting, all samples of a given series using the same aggregate of a known hardness, calibrating the exposed lengths of said investigative probes segregated in series according to aggregate hardness in terms of compressive strength of the concrete as checked by an independent measurement of the compressive strength of the respective samples using standard testing procedures, and recording the respective strengths of said samples coordinated with the exposed lengths of the associated probes segregated according to aggregate hardness, all of said probes being driven by means of a powder actuated firing device having a barrel with an open-ended bore, each of said probes being an elongated metal probe having a driving head and having a penetrating nose portion including a conical point with a fixed angle between 60* to 135* capable of cracking pieces of coarse aggregate; in every such test using (1) a probe of substantially uniform physical dimensions and structure, (2) a powder charge of a carefully controlled mixture and exactly measured weight, (3) a substantially uniform spacing of the open end of said barrel close to the surface of the concrete, (4) a substantially uniform initial position of the probe relative to the powder charge in a zone in the barrel spaced from the surface of the concrete to be tested, and (5) a substantially uniform clearance between the driving head of said probe and the bore of said barrel; the powder charge being sufficient to drive each said probe below a shear failure cone in said concrete and to cause the probe to crack the coarse aggregate in the concrete; and thereafter driving a test probe into an unknown concrete sample whose aggregate hardness is known and keeping all conditions uniform with those under which the investigative probes were driven, then measuring the exposed length of said test probe as giving a measure complementary to the depth of penetration to determine the compressive strength of the concrete tested, by using said recorded calibration of an identical probe driven under the same conditions into concrete, whose aggregate is of the same hardness.

Claim 17

The method of performing a dependably reproducible test for the compressive strength of concrete composed of a mixture of sand, cement and an aggregate of known hardness, any time after setting with commercially acceptable accuracy, comprising driving a number of investigative probes into a plurality of series of concrete samples at various times after setting, all samples of a given series using the same aggregate of a known hardness, calibrating the exposed lengths of said investigative probes segregated in series according to aggregate hardness in terms of compressive strength of the concrete as checked by an independent measurement of the compressive strength of the respective samples using standard testing procedures, and recording the respective strengths of said samples coordinated with the exposed lengths of the associated probes segregated according to aggregate hardness, all of said probes being driven by means of a powder actuated firing device having a barrel with an open-ended bore, each of said probes being an elongated metal probe having a driving head and having a penetrating nose portion including a conical point with a fixed angle between 60* to 135* capable of cracking pieces of coarse aggregate; in every such test using (1) a probe of substantially uniform physical dimensions and structure, (2) a powder charge of a carefully controlled mixture and exactly measured weight, (3) a substantially uniform spacing of the open end of said barrel close to the surface of the concrete, (4) a substantially uniform initial position of the probe relative to the powder charge in a zone in the barrel spaced from the surface of the concrete to be tested, and (5) a substantially uniform clearance between the driving head of said probe and the bore of said barrel; the powder charge being sufficient to drive each said probe below a shear failure cone in said concrete and to cause the probe to crack the coarse aggregate in the concrete; and thereafter driving a test probe into an unknown concrete sample whose aggregate hardness is known and keeping all conditions uniform with those under which the investigative probes were driven, then measuring the exposed length of said test probe as giving a measure complementary to the depth of penetration to determine the compressive strength of the concrete tested, by using said recorded calibration of an identical probe driven under the same conditions into concrete, whose aggregate is of the same hardness.