LWD testing in Nottingham.

Same-day and next-day dates are often available, subject to the schedule. Nottingham is about an hour and a half from our laboratory by the M1, and an LWD visit needs only a technician and portable equipment, so it is straightforward to fit in. We do not guarantee an attendance time. Ring 0115 786 5656 to check dates.

It tells you how stiff the layer under the plate is. The equipment drops a known weight onto a plate and records how far the surface deflects. A 10 kg weight falling onto a 300 mm plate is typical, with a few seating drops to bed the plate followed by measuring drops that are averaged. The result is a dynamic surface modulus in megapascals, calculated from the force applied and the deflection it produced. It is a stiffness measurement, not a bearing capacity test, which is why the target has to come from your designer.

Yes, well. Weathered Sherwood Sandstone is a dense, free-draining sand with a genuine elastic response, which is what the equipment needs. The surface should be trimmed level and lightly compacted so the plate seats evenly. Loose, dry sand at the surface can ravel under the plate, so we bed the plate carefully and note the surface condition.

Not reliably once it is wet. The weathered mudstone behaves as a clay, deforms plastically and gives little elastic recovery for the equipment to read. At formation level on the mudstone an in-situ CBR is the better test. Use the LWD on the capping and sub-base above it, where it gives quick, repeatable results.

Your specification or designer sets it. For pavements, DMRB CD 225 defines foundation classes by surface modulus, starting at 50 MPa, and the specification says which class applies and how it must be demonstrated. For warehouse floor slabs the engineer normally sets a project value. Tell us the target and the report shows each position against it.

Yes. Stabilised layers have a clear elastic response and the LWD is a common way to check them, usually after the curing period your specification sets. South of the Trent, where the Mercia Mudstone carries gypsum, make sure sulfate testing was done before the binder was chosen, because a stabilised layer can pass its stiffness test and still heave later if the sulfate content was high.

There is no single British Standard for the lightweight deflectometer. Testing usually follows the equipment manufacturer’s procedure alongside a recognised method such as ASTM E2583. On highway schemes the requirement comes from the specification, with performance testing of pavement foundations covered by Series 800 of the Specification for Highway Works.

Roughly one to one and a half plate diameters, so about the top 300 to 450 mm with a 300 mm plate. It checks the layer you have placed, not the ground well below it. Over backfilled gravel pits or colliery fill, a thin layer gives a composite reading of the layer and the fill beneath, so a DCP alongside is worth having.

For checking a layer is uniform, often yes. For proving a piling platform or crane hardstanding, usually no, because those designs are checked against a plate bearing result at the design pressure. Plate tests at the critical positions with LWD across the rest is a common and sensible plan. Check with your designer first.

It can be estimated, but dynamic stiffness and direct CBR are different measurements and the relationship depends on the material. Any conversion must be appropriate to the material and agreed for the project, and should be reported as derived. If the adopting authority wants a CBR at formation, a CBR test is the cleaner answer.

Hixtra holds UKAS accreditation to ISO/IEC 17025 under schedule number 8996. Accreditation is granted method by method, not to the company as a whole, so it applies only to the tests listed on our current schedule. Ask us to confirm the accreditation status of LWD testing when you enquire, particularly if your specification requires accredited results, and we will tell you before you book.

Every visit is quoted from the site postcode. With no reaction vehicle and only minutes per position, the cost per test is low compared with plate bearing. The price depends mainly on the time on site, and we can often combine Nottingham with work in Derby, Loughborough or Leicester. Send the postcode, the area and your dates.

No. Hixtra has one laboratory, in Milton Keynes, and every Nottingham visit is run from there. The 0115 number rings through to the same team as our other numbers. With the M1 between us, that makes little practical difference to dates.