A repair mortar has to bond to old concrete that is denser, drier and stiffer than itself, follow the structure’s movement without debonding, and — for structural classes — reach 45 MPa with almost no shrinkage. No single additive does this. Polymer powder provides bond and ductility, cellulose ether gives the thixotropy that holds 30 mm overhead, a polycarboxylate brings the water/cement ratio down to structural levels, fibre and a defoamer control cracking and density. This page sets out the Accurate®, Landercoll® and NOVASTAR® grades for each EN 1504-3 class with starting dosages, a troubleshooting table and a laboratory starting formulation.
| Class | Use | Compressive strength (28 d) | Adhesion (EN 1542) | Other key requirements | Additive priorities |
|---|---|---|---|---|---|
| R1 | Non-structural cosmetic repair, reprofiling | ≥ 10 MPa | ≥ 0.8 N/mm² | Workability, sag resistance | Cellulose ether, 2–3 % RDP |
| R2 | Non-structural, thicker cosmetic repair | ≥ 15 MPa | ≥ 0.8 N/mm² | Crack control, adhesion after thermal cycling | Cellulose ether, 3–4 % RDP, fibre |
| R3 | Structural repair, moderate loads | ≥ 25 MPa | ≥ 1.5 N/mm² | E-modulus ≥ 15 GPa, restrained shrinkage/expansion ≥ 1.5 N/mm², chloride ≤ 0.05 % | Low w/c via PCE, 2–3 % RDP, fibre, defoamer |
| R4 | Structural repair, high loads, carbonation barrier | ≥ 45 MPa | ≥ 2.0 N/mm² | E-modulus ≥ 20 GPa, capillary absorption ≤ 0.5 kg/m²·h^0.5, carbonation resistance | PCE 540P / 590P, silica fume, 1–2 % RDP, fibre, defoamer, shrinkage control |
| Additive | Grades (TDS data) | R1 / R2 cosmetic, hand-applied | R3 structural, trowel or spray | R4 structural, high strength |
|---|---|---|---|---|
| Accurate® RDP | 5045N flexible (Tg −10 ± 5 °C; TDS lists repair mortar); 5011N rigid (Tg 10 ± 5 °C); 8048H very strong hydrophobic, instant-dissolving (TDS lists repair mortar); 9028E (Tg 5 °C) / 9055E (Tg −15 °C) acrylic–silane (TDS: repair mortars) | 5045N 3–4 % (ductility, bond on old concrete) | 5011N or 8048H 2–3 % | 5011N 1–2 % (bond, chloride barrier) |
| Landercoll® cellulose ether | K100 / EM100 (45,000–60,000 mPa·s Brookfield; TDS: repair mortar); K75 / EM80 (35,000–45,000); EM40HT (18,000–23,000; TDS: repair mortar, heat resistance “excellent”); K04 (300–500; self-leveling grade) | K100 / EM100 0.20–0.30 % (thixotropy for vertical and overhead) | EM40HT 0.08–0.15 % | K04 0.03–0.06 % (cohesion only) |
| NOVASTAR® PCE, 530P–580P series (product-page data) | 540P (sulfoaluminate-cement water reducer, water-reduction rate 34 %) recommended for rapid repair and pavement repair mortar; 530P and 580P compatible | — | 540P or 530P 0.15–0.30 % | 540P or 580P 0.30–0.50 % |
| NOVASTAR® PCE (TDS series) | 590P high water reduction (≥ 25 %, 97 % solids, chloride ≤ 0.02 %); 600P slump retention; 590FP early strength (12 h strength ratio > 240 %). TDS dosage 0.1–0.5 % of cementitious material | — | 590P 0.15–0.30 % | 590P 0.30–0.50 % (600P share for hot weather, 590FP for rapid return to service) |
| NOVASTAR® powder defoamer | P805 standard; P806 alkali-resistant; P807 low-temperature | P805 0.1 % | 0.1–0.2 % | 0.2–0.3 % |
| NOVASTAR® starch ether | ST3152 (machine-applied mortars: thixotropy, anti-sag; residue on ignition ≤ 3 %); ST1506-A (hand-applied) | ST1506-A 0.03–0.05 % (overhead work) | ST3152 0.02–0.05 % (sprayed repair) | — |
| PP fibre | 6–12 mm monofilament | 0.1 % | 0.1–0.15 % | 0.1–0.15 % |
| NOVASTAR® SHP | SHP75 / SHP80 (TDS dosage 0.1–0.5 %) | 0.2–0.3 % for exposed façades | — | — |
| Third-party components | Silica fume, shrinkage-reducing admixture, expansive agent, calcium formate | — | silica fume 3–5 % | silica fume 5–8 %, SRA, expander |
Dosages are percentages of the total dry mix for laboratory starting points; the technical data sheets do not prescribe mortar dosages. In R3/R4 mortars the cellulose ether dosage falls sharply because strength, not sag, is the limiting property.
Cause-by-cause diagnosis of bond failures, with pull-off test procedure, is in Repair mortar bond failure diagnosis.
| Symptom | Likely cause | Adjustment |
|---|---|---|
| Pull-off < 1.5 N/mm² with failure at the interface | Dry, dusty or laitance-covered substrate; low polymer | Prepare to CSP 3–5 and pre-wet to SSD; RDP ≥ 3 %; scrub first layer in |
| Hollow sound after 7 days | Shrinkage pulled the patch away | Lower w/c with 590P; fibre 0.1 %; SRA; cure 3–7 days wet |
| Sags or falls off overhead at 20 mm | Insufficient thixotropy | K100 / EM100 0.25 %; ST1506-A 0.03 %; apply in 10–15 mm passes |
| Cracks across the patch in 24 h | Plastic shrinkage in sun/wind | Fibre 0.1 %; cellulose ether +0.05 %; protect and cure |
| Low 28-day strength for R4 | w/c too high; air | 590P 0.4 %; P805 0.25 %; silica fume; check water dosing on site |
| Pinholes, low density, high permeability | Air from polymer and mixing | P805 0.2–0.3 %; slower mixing |
| Mortar sticks to the trowel, drags | Cellulose ether too high; polymer too flexible for the class | Reduce to EM40HT 0.10 %; move to 5011N |
| Rebound and blockages in wet spraying | Rheology not matched to the pump | ST3152 0.03 %; EM40HT; P805; constant water |
| Working time too short in summer | Fast slump loss | Replace part of 590P with 600P (slump retention) |
| Efflorescence on façade repairs | Water movement | SHP 0.3 %; hydrophobic RDP 8048H |
| Component | R2 cosmetic repair mortar | R4 structural repair mortar |
|---|---|---|
| CEM I 42.5 R / 52.5 R | 30–35 % | 38–42 % |
| Silica fume | — | 5–6 % |
| Quartz sand 0–1 mm / 0–2 mm | 55–60 % | 45–50 % |
| Limestone filler | 5–8 % | 3–5 % |
| Accurate® RDP | 5045N 3.5 % | 5011N 1.5 % |
| Landercoll® cellulose ether | K100 0.25 % | K04 0.04 % |
| NOVASTAR® PCE | — | 540P or 590P 0.40 % |
| NOVASTAR® defoamer P805 | 0.10 % | 0.25 % |
| NOVASTAR® starch ether ST1506-A | 0.03 % | — |
| PP fibre 6 mm | 0.10 % | 0.12 % |
| Calcium formate | 0.5 % | — |
| Shrinkage-reducing / expansive agent | — | per supplier |
| Water | ≈ 17–19 % | ≈ 13–15 % |
Starting points only; EN 1504-3 testing (strength, adhesion, restrained shrinkage, E-modulus, chloride, carbonation for R4) must be completed on the final blend.
Repair mortars are specified products: once a formulation has passed EN 1504-3, the additive grades cannot change. LANDU manufactures Landercoll® cellulose ethers, Accurate® polymer powders and NOVASTAR® PCE, defoamers and fibres in its own three plants in Shandong (75,000 t/year) under ISO 9001 with batch certificates, so a grade approved in your lab is the grade delivered for years. The portfolio is REACH-compliant; European stock is held with partners in several countries, including Greece, Spain and Italy; factory lead time 7–15 working days; 25 kg bags on pallets (cellulose ether 500–600 kg, RDP 600–1,300 kg per pallet). Shelf life per TDS: K100 / EM100 two years, RDP one year, PCE powder twelve months.
A rigid grade — Accurate® 5011N (Tg 10 ± 5 °C) at 1–3 % — so that the E-modulus requirement (≥ 15 / 20 GPa) is met while bond and chloride resistance improve; 8048H where the repair must also be a water and chloride barrier. Flexible 5045N and the acrylic–silane 9028E / 9055E are reserved for R1/R2 cosmetic repairs where ductility matters more than stiffness.
It depends on the class. Hand-applied cosmetic repair needs 0.20–0.30 % of Landercoll® K100 / EM100 for sag resistance; structural trowel mortars 0.08–0.15 % of EM40HT; high-strength R4 only 0.03–0.06 % of the low-viscosity K04 for cohesion. More than that costs strength and bond.
R3/R4 strength and the capillary absorption limit of R4 require a water/cement ratio around 0.35–0.40, which cannot be mixed and placed without a superplasticizer. NOVASTAR® 590P (water-reduction rate ≥ 25 % on the TDS) at 0.3–0.5 % provides the water reduction while keeping the mortar workable for 30–45 minutes; blend in 600P for longer placement windows. In rapid-setting and sulfoaluminate repair mortars, 540P is the recommended grade.
They do different jobs. Fibre controls plastic-shrinkage cracks in the first 24 hours; RDP provides bond and long-term ductility. Most repair mortars above 10 mm thickness use both.
Sound concrete roughened to CSP 3–5, free of laitance and dust, pre-wetted to saturated surface-dry with no standing water. With poorer preparation, no additive dosage will reach the EN 1542 adhesion values.
Our laboratory runs compressive and flexural strength, pull-off adhesion on prepared concrete slabs, restrained shrinkage screening, air content and capillary absorption on customer formulations, and recommends grades and dosages for the target class. Full certification testing is carried out by a notified body.
Yes. Landercoll® cellulose ethers, Accurate® polymer powders and NOVASTAR® PCE, defoamers and fibres are made in LANDU's own three plants in Shandong Province (75,000 t/a); headquarters and laboratory are in Jinan. Minimum order 1,000 kg per grade in 25 kg bags; stock grades ship in 7–14 days, FOB or CFR/CIF to European ports; free 500 g – 1 kg samples with TDS and batch COA.
A cellulose ether for water retention and non-sag consistency (K100 / EM100 at 0.20–0.30 % for hand-applied mortar; EM40HT where heat resistance matters), an RDP for bond to old concrete and ductility (5045N for R1–R3, 8048H or 9055E where water exposure adds to the brief; 5011N where a rigid, economical bond is enough), a PCE for strength at low water (590P, 0.15–0.50 % by class), a powder defoamer, and PP fibre for plastic-shrinkage control. Structural R4 mortars add silica fume and a shrinkage-reducing or expansive component.
Both retain water and build consistency in the same way at moderate temperature. MHEC (HEMC) keeps its viscosity and open time above 30 ℃ and is the grade family the TDS rate "excellent" for heat resistance, so it is the choice for sprayed repair in summer and for hot climates. HPMC is the cost-efficient choice for hand-applied repair in temperate conditions. The grades whose TDS list repair mortar are K75 and K100 (HPMC) and EM40HT, EM60, EM80 and EM100 (HEMC). Test the two side by side on the same substrate before fixing the formulation.
EN 1504-3 classes apply to the finished repair product, not to an individual HPMC, RDP or PCE. What we supply is the additive package and the laboratory screening (compressive strength, pull-off adhesion, restrained shrinkage) that shows whether a formulation is heading for R3 or R4 before you pay for third-party testing. The declaration of performance remains the mortar manufacturer's.
We return RDP, cellulose ether, PCE and fibre recommendations with dosages within two working days and ship samples free of charge.
LANDU — Committed to Every Gram.
