Materials Testing & Inspection

Holt Engineering, Inc. has assembled a staff of professional engineers, licensed field technicians, and support staff to provide our clients with outstanding service and quality in materials testing and inspection services.

Our technicians are highly experienced NICET and ACI certified. We have a complete in-house laboratory for testing soils, rock, and concrete materials. Our in-house laboratory is accredited in many of the required geotechnical and testing ASTM standards. Per AASHTO accreditation requirements, we participate in the AASHTO re:source and CCRL soil and concrete proficiency testing and inspection programs. We are set up to perform Atterberg limits, sieve analyses, moisture density curves (proctors), oven dry moisture testing, permeability testing, unit weights, concrete mix designs, concrete compression testing, specific gravities, hydrometer testing, unconfined compression testing, and asphalt density testing.

Field testing services include concrete testing (slump, air content, yield, and making cylinders, cubes, and/or beams), pier hole and beam excavation inspections (diameter of hole, beam size, depth, reinforcement, cleanliness and location), structural steel and reinforced steel inspection for both above grade iron structures and below grade steel piping, wood truss inspection, post tension cable stressing, fire-proofing, and other services as needed per the project testing specifications.

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Windsor probe concrete testing is used as a non-destructive test method to test compression strength of the actual hardened concrete in a structure.

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Pier inspection includes verifying location, pier hole diameter, depth of hole, embedment, reinforcement cages, groundwater, plumbness and cleanliness of hole, tremmie length, casing and concrete testing.

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Concrete testing and inspection in the field includes noting the properties of fresh concrete such as temperature, slump and air content, verifying mix design, concrete supplier and location of concrete being placed. Cylinders or cubes made in the field are broken at a later time in order to determine compressive strength.


Holt Engineering is committed to providing quality and accurate site inspections and construction materials testing services. Our firm is AASHTO accredited in ASTM “Standard Specification for Agencies Engaged in Construction Inspection and/or Testing”; ASTM C-1077 “Standard Practice for Laboratories Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Laboratory Evaluation and AASHTO R-18 “Standard Recommended...

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Utility backfill inspections include visual observation of trenches, placement of pipe bedding material, placement of pipe and trench backfill compaction and density testing.


The goal of reinforced steel inspection is to ensure compliance with the project plans and specifications for many types of structures including slabs, bridges, columns and roadways. The reinforced steel bars are inspected for diameter, shape, grade, spacing, stirrups, tie spacing and chair supports.

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Cable stressing involves pre-pour inspections as well as observation of post-tension stressing. Holt’s engineering technicians are experienced and fully qualified to perform these types of inspections which may include checking size, grade and type of cables, spacing, groupings, layout over columns, verification of concrete compressive strengths prior to post-tension stressing, checking gauge pressures, measuring elongations and compiling...


Field Density Testing includes testing on subgrade, select fill, roadway base and utility trench backfill. Tests will be made on each lift of fill prior to placement of any subsequent lifts. The technician will verify that appropriate proctor is being used and that material used as fill (including select fill or roadway base) meets any written requirements in the plans and specifications. For lime stabilized subgrades, field sieves are...


Asphalt testing includes obtaining grab samples from the batch during each day’s placement or as specified in the plans. Bag samples will be transported to an outside accredited lab for testing extraction, gradation, specific gravity and HVEEM stability. Our firm will cut cores within the following week and verify thickness and bulk specific gravity.