Research on the Properties and Application of Inorganic Modified Cement Grout

In the operation of municipal underground pipelines, issues such as loosened soil around pipe exteriors, gaps in pipe walls, seepage in surrounding rock, and void defects frequently occur. Ordinary cement grout has coarse particles that struggle to penetrate fine fissures, resulting in limited sealing and anti-corrosion performance. Inorganic modified cement grout, with its hydration system optimized through mineral modification, offers excellent permeability, forms a dense and stable consolidated body, and combines the advantages of slight expansion with durability and corrosion resistance. It is widely used in substrate pretreatment and defect repair projects such as filling around pipelines, pipe-wall anti-corrosion treatment, and anti-seepage reinforcement of surrounding rock along pipelines.

01 · Material Composition and Preparation Principles

Composed of four categories of raw materials: cementitious base material, ultra-fine mineral admixtures, inorganic reactive modifying components, and high-efficiency admixtures.

1. Cementitious base material: mainly ordinary Portland cement, providing basic hydration and cementing capacity;
2. Mineral admixtures: ultra-fine powders of fly ash, silica fume, and mineral powder, optimizing particle gradation;
3. Reactive modifying components: possess pozzolanic activity, regulating the later-stage hydration reaction;
4. High-efficiency admixtures: polycarboxylate high-efficiency water reducer, ensuring grout fluidity and reducing the risk of bleeding and segregation.

Mainly based on the theory of closest particle packing, with three core underlying logics:

1. Particle gradation filling: ultra-fine powders fill the gaps between cement particles, widening the grout's penetration channels and improving injectability;
2. Secondary hydration densification: the reactive components undergo a pozzolanic reaction with the calcium hydroxide produced by cement hydration, continuously generating C-S-H gel that fills internal capillary pores;
3. Shrinkage defect control: optimized component ratios achieve a slight expansion effect, offsetting hardening-induced drying shrinkage and preventing gaps or voids from forming at the interface between the consolidated body and the substrate.

02 · Core Performance and Indicators

1. Grout fluidity ≥180 mm, with good pumpability, meeting the requirements of deep grouting construction;
2. Grout bleeding rate ≤3%, more than 60% lower than that of pure cement grout, making it less prone to stratification and sedimentation;
3. 28-day compressive strength of the consolidated body ≥35 MPa;
4. Exhibits slight expansion characteristics; the later-stage drying shrinkage rate after hardening is significantly lower than that of ordinary cement grout;
5. Can penetrate micro-fissures with a width ≥0.1 mm, suitable for pretreatment and anti-corrosion applications in the surrounding rock and pipe-wall gaps around underground pipelines (referencing relevant experimental research literature on modified cement-based grouting materials in MDPI).

03 · Core Advantages

Stronger penetration capability

The raw material particles are optimized in proportion, enabling penetration into fine cracks that ordinary cement grout cannot reach, filling the micro-gaps between the pipe's outer wall and the surrounding soil, and achieving deep filling and anti-seepage sealing around the pipeline.

Dense and stable consolidated body

The pozzolanic reaction continues throughout the hardening process, optimizing the internal structure; the resulting consolidated body has few pores and outstanding impermeability and soil-corrosion resistance, providing long-term protection of the pipe's outer wall against water and soil erosion.

Slight expansion with low shrinkage

With controllable slight-expansion characteristics, it offsets the shrinkage deformation produced during hardening, preventing gaps or voids from forming between the grout and the pipe's outer wall or surrounding rock, maintaining a tight, long-lasting bond, and ensuring the anti-corrosion sealing does not fail.

Green inorganic system

Composed purely of inorganic minerals, containing no organic solvents or harmful substances — environmentally friendly. Resistant to water and to corrosion from groundwater and soil, it is suitable for long-term service in the damp operating conditions of underground pipelines, continuously providing protection to the pipe wall.

Convenient construction

The grout has excellent fluidity and a simple mixing process. It is compatible with various pipe-exterior and pipeline-substrate pretreatment scenarios, has a low operational threshold, efficiently completes gap-filling and anti-corrosion protection work, and effectively shortens the construction cycle for pipeline repair.