Civil Engineering Association

Structural Capacity of Rammed Earth in Compression

Rammed earth walls are formed by compacting subsoil in thin layers inside temporary supporting formwork. An ancient form of construction, rammed earth has in recent years, together with other earth building methods, been increasingly used structurally in a range of contemporary buildings in many countries around the world. Though current structural design procedures for earth walls, including rammed earth, in general use provisions based on structural masonry standards, this approach has never been satisfactorily validated. This paper presents experimental results from material and large-scale testing and develops a simple theoretical model, applied to rammed earth columns subject to concentric and eccentric axial compression loading. An analytical model, using a basic strut theory, shows favorable correlation with the experimental results for all load eccentricities.

---

Soil Property Criteria for Rammed Earth Stabilization

This study relates value ranges of natural soil properties (plasticity, texture, and shrinkage) to the degree of predisposition of soils to stabilization for rammed earth wall construction. A total of 219 strength determinations were made on 104 soils compacted and stabilized with cement and/or lime and/or asphalt. Using a 2 MPa compressive strength criterion as the measure of stabilization success, soil property value ranges were related to the proportion of samples exceeding the criterion. Linear shrinkage (LS) and plasticity index (PI) are found to be the best discriminators of soil predisposition, with textural variables being useful secondary discriminators. “Favorable” soils, with stabilization success rates of ≥80%, include those with: (1) LS<6.0% and PI<15%; and (2) LS 6.0–11.0%, PI 15–30%, and sand content <64%. These soils were stabilized with treatments averaging 4.2% cement and 1.8% lime, with individual treatments ranging from 4–8% total cement and/or lime. “Unfavorable” soils, with stabilization success rates of <60%, include those with LS 6.0–11.0, PI 15–30, and sand content ≥64%, or with LS>11.0, PI>30. These findings should assist rammed earth engineers to more easily select a suitable soil and to minimize resources spent on preconstruction stabilization trials.

Both papers inside 1.16Mb Rar file / no pass.

Correlation of Rheological Properties to Durability and Strength of Hardened Concrete

Premature deterioration of concrete structures has created awareness and concern about the durability of concrete. Concrete mixtures used in the construction of residential basement walls and foundations have a high water to cement (w/c) ratio (w/c>0.6) and low cement content (<280 kg/m[sup 3]). The result is friable concrete with a highly porous surface layer and high potential for cracking. The defects have a direct impact on the durability of concrete. This experimental study examines the effects of three parameters—mix design, formwork, and consolidation—on the quality of the surface of high w/c concrete. The fresh concrete is characterized using its rheological properties—in particular, its yield stress and plastic viscosity. Pulse velocity, pull-off strength, and compressive strength were measured to evaluate the quality and the mechanical properties of the hardened concrete. The durability of the hardened concrete was evaluated by measuring its surface transport properties—namely, its air permeability and sorptivity. The results show that it is possible to correlate the rheological properties of fresh concrete to the mechanical and permeation properties of the hardened concrete.

General Viscoelastic Solutions for Multilayered Systems Subjected to Static and Moving Loads

Determination of Viscoelastic Poisson's Ratio and Creep Compliance from the Indirect Tension Test