Australian Society for Concrete Pavements The Role & Influence of Aggregates in Lean Mix Concrete Subbase (LMCS)

The Role & Influence of Aggregates in LMCS Today We will cover: What aggregates are used in Lean Mix Concrete Subbase (LMCS)? What properties of these aggregates are important? The role aggregates play in performance of LMCS How to avoid potential problems in LMCS by correct aggregate selection and monitoring.

What aggregates are used in Lean Mix Concrete Subbase (LMCS)?? The Role & Influence of Aggregates in LMCS Coarse Aggregate- normally 20mm,14mm, 10mm or 7 mm Fine Aggregate- Coarse Sand (or Manufactured Sand) and Fine Sand – Dune, river or other fine sands. R82- Aggregates-Tested & delivered from dedicated stockpiles or material onsite

Aggregates maybe: From an established source with a history of test results on aggregate performance. From a more recently established new deposit or process or won from site, tested and approved Where are these quarry aggregates from? The Role & Influence of Aggregates in LMCS Aggregates must be tested to confirm their properties are consistent and measurable – AS

AS / RTA R82 Grading- AS individual and combined Individual- 1 /400T Combined by calc- 1/800T or Wet sieved- with trial mix or within12mths prior R82- Production tolerances on Combined grading What properties of these aggregates are important? The Role & Influence of Aggregates in LMCS

Grading of each individual aggregate is important as it affects the total combined grading. What properties of these aggregates are important? The Role & Influence of Aggregates in LMCS

AS :1 (<35%) and 3:1 (<10%) Concrete Aggregates – Particle Shape The Role & Influence of Aggregates in LMCS More Desirable Less Desirable

Mat <75um ( F<10%, C< 2%) Mat <2um (F < 1%, C <1%) Organic impurities (<0.5%) Sugar Content (<1part:10,000) Salts- Cl (<0.8kg/m3), S0 3 ( <5%) from aggregates or in hardened concrete. Concrete Aggregates – Impurities The Role & Influence of Aggregates in LMCS

Durability –Wet Strength (> 50kN) –Wet/Dry Strength Variation (<35%) –Sodium Sulphate Soundness (<12%) Concrete Aggregates – Properties The Role & Influence of Aggregates in LMCS

Aggregates occupy the largest volume within the concrete mix hence have a very large influence on concrete mix performance. The Role Aggregates play in LMCS The Role & Influence of Aggregates in LMCS

Property Concrete workability Place ability Surface finish Bleed Drying shrinkage Mix Economy Effected By …..………...Grading & Shape ………….…Grading, Shape & quantity …………….Fine aggregate Grading ………………Grading, Silt and Fines content ……Type & amount of aggregate …………….Shape, grading, strength The Role & Influence of Aggregates in LMCS

Avoiding Problems in LMCS – Control charting of Individual and Combined Grading G9 = C6 x C9 + D6 x D9 + E6 x E9 + F6 x F9 =100%

The Role & Influence of Aggregates in LMCS Dedicated Stockpiles- Grading / 400T Avoiding Problems in LMCS – Lot T Lot T Lot T Lot T Lot T 5 sample increments First 2000 T Aggregate stockpile Need to understand and audit how the quarry is conducting this throughout the project?

The Role & Influence of Aggregates in LMCS Aggregate Sampling- AS Samples- at least five sample increments of approx equal mass. (E.g. 20mm aggregate- 5 sample increments of 4kg min each). Table 2 Minimum Mass per Sample Nominal size, mm <5 Mass, Kg graded material

The Role & Influence of Aggregates in LMCS Avoiding Problems in LMCS – Monitoring of Clay & silt in natural fine aggregates Monitor bleed of plastic concrete Compare Bleed with combined aggregate and individual fine aggregate grading – especially with mixes containing Man Sands.

The Role & Influence of Aggregates in LMCS Aggregates influence CONCRETE Questions?